Promethazine has been one of the most widely used medicines in UK pharmacy since the 1950s.
The compound was developed by Rhône-Poulenc as part of the phenothiazine research that also produced chlorpromazine, the first antipsychotic medicine. As a result, promethazine has structural similarity to phenothiazine antipsychotics. However, it has primarily antihistamine and sedating effects rather than antipsychotic effects.
Four licensed uses in one tablet
Promethazine 25mg Tablets are licensed in the UK for four distinct clinical uses:
Allergic conditions: symptomatic treatment of allergic conditions of the upper respiratory tract and skin, including allergic rhinitis, urticaria, and as an adjunct in anaphylactic reactions to drugs and foreign proteins
Nausea, vomiting, and motion sickness: the antiemetic and anti-motion-sickness effects make promethazine useful for short-term travel sickness and for nausea from various causes
Sedation: for both adults and children over 6, where short-term sedation is clinically appropriate
Short-term insomnia in adults: as a sedating antihistamine for sleep, typically alongside addressing underlying sleep hygiene factors
Few medicines cover this breadth of indications in one tablet. However, in modern UK practice, each indication is often better served by a more targeted alternative.
The shift away from first-generation antihistamines
Second-generation antihistamines (cetirizine, loratadine, fexofenadine, bilastine, desloratadine, levocetirizine, rupatadine) were developed to retain the histamine-blocking efficacy with substantially reduced CNS penetration. As a result, they produce equally effective allergy symptom control with much less drowsiness and far fewer anticholinergic effects.
For most UK patients with allergic conditions in 2026, the first-line choice is a non-sedating second-generation antihistamine. Furthermore, NHS, NICE, and BSACI guidance reflect this. The MHRA has issued multiple statements over the years recommending careful consideration before using first-generation sedating antihistamines.
Where promethazine still fits in modern practice
Despite the shift to newer alternatives, promethazine retains specific clinical roles:
Allergic symptoms disrupting sleep: where the sedation at bedtime is genuinely useful. For example, urticaria with night-time itching
Patients not responding adequately to non-sedating antihistamines: some patients with refractory urticaria benefit from adding or switching to a first-generation antihistamine at night
Severe acute allergic skin conditions with prominent itching: where the combination of histamine blockade plus sedation provides better symptom relief
Short-term sedation for specific situations: pre-operative anxiety, anticipated stressful events under medical guidance
Motion sickness: promethazine is one of the more effective anti-motion-sickness medicines, used either prophylactically before travel or for established motion sickness
Nausea and vomiting where ondansetron, cyclizine, or metoclopramide aren’t suitable or available
Short-term insomnia in adults: as an option when other approaches haven’t worked. However, behavioural approaches and CBT-I are first-line
How promethazine compares to other antihistamines
The UK antihistamine landscape in 2026 offers a range of options:
Second-generation non-sedating (first-line for most patients): loratadine 10mg, cetirizine 10mg, fexofenadine 180mg, bilastine 20mg, desloratadine 5mg, levocetirizine 5mg, rupatadine 10mg. Notably, these provide once-daily dosing, minimal sedation, minimal anticholinergic effects, and no significant interactions for most patients
First-generation sedating (specific situations): promethazine (Phenergan), cyproheptadine (Periactin), chlorphenamine (Piriton), hydroxyzine (Atarax), diphenhydramine (Nytol original). Used where sedation is wanted or where non-sedating options haven’t been enough
Intranasal antihistamines: azelastine (alone or as Dymista with fluticasone propionate), levocabastine. Useful for localised nasal allergic symptoms with faster onset
H2 antagonists used in allergic contexts: famotidine, nizatidine. These can be combined with H1 antihistamines for refractory urticaria
Intranasal corticosteroids: Beconase, Nasacort, Benacort, mometasone, fluticasone. Address the inflammatory component rather than blocking histamine
Leukotriene receptor antagonists: montelukast, with appropriate caution per MHRA neuropsychiatric warnings
Allergen-specific immunotherapy: Grazax, Acarizax, Itulazax for severe disease driven by specific allergens
Promethazine’s distinctive profile
Within the first-generation antihistamine class, promethazine has features that distinguish it from alternatives:
Strongest sedating profile: substantially more sedating than chlorphenamine, somewhat more than cyproheptadine. Therefore, this is most useful when sedation is wanted
Anti-emetic effects: more pronounced than other first-generation antihistamines. As a result, this makes promethazine particularly useful for motion sickness and nausea
Phenothiazine class effects: structural similarity to antipsychotics produces additional pharmacological effects but also additional precautions (QT prolongation, dystonic reactions, photosensitivity)
Long history: over 75 years of clinical use with well-characterised safety profile
Multiple indications in one tablet: useful where patients need multiple effects from one medicine
Patient groups where promethazine warrants extra caution
Several patient groups should generally avoid promethazine or use it with particular caution:
Children under 6 years: contraindicated. Promethazine carries serious respiratory depression risk in this age group, with reported fatalities particularly under age 2
Older patients (typically over 65): MHRA guidance and the Beers Criteria caution against routine sedating antihistamine use. The reasons: fall risk, cognitive impairment, urinary retention, anticholinergic burden, and CO2 retention risk. Therefore, non-sedating alternatives are strongly preferred
Patients with significant respiratory disease (COPD, severe asthma): respiratory depression risk and reduced respiratory drive
Patients with prostate enlargement: anticholinergic effects can cause urinary retention
Patients with glaucoma: anticholinergic effects can precipitate acute angle-closure
Patients with significant cardiovascular disease, particularly with QT prolongation risk or arrhythmias
Patients taking MAOI antidepressants (or within 14 days of stopping): contraindicated
Patients taking other sedating medicines: alcohol, benzodiazepines, opioid analgesics, sedating antidepressants. Cumulative sedation can be significant
Patients taking other anticholinergic medicines: amitriptyline, oxybutynin, hyoscine, some Parkinson’s disease medicines. Cumulative anticholinergic burden
Patients with cognitive impairment, dementia, or delirium: sedating antihistamines worsen cognitive function
Patients driving or operating machinery: significant impairment risk
Patients with epilepsy: theoretically lowers seizure threshold
Children with suspected Reye’s Syndrome features
We at Courier Pharmacy supply Promethazine 25mg Tablets under prescriber supervision. Our prescriber screens carefully for these considerations.
Key features and specifications
Active ingredient: promethazine hydrochloride 25mg per tablet
Form: pale blue film-coated tablet (Phenergan brand marked PN 25; generic appearance may vary)
Pack size: 28 tablets (lasts 9 to 28 days depending on indication and dose)
Licensed indications: allergic conditions (allergic rhinitis, urticaria, anaphylactic reactions); nausea, vomiting, motion sickness; sedation in adults and children over 6; short-term insomnia in adults
Standard adult dose for allergic conditions: 25mg at night, or 10mg to 20mg two to three times daily; maximum 75mg per day
Sedation/sleep dose: 25mg to 50mg at night
Motion sickness dose: 25mg taken 1 to 2 hours before travel; can repeat every 6 to 8 hours up to maximum 75mg per day
Onset of action: 20 minutes for sedating effect; 1 to 2 hours for peak antihistamine effect
Duration of effect: 4 to 6 hours for antihistamine effect; sedation can persist into the next day, particularly at higher doses
Supplied by: Courier Pharmacy, UK GPhC-registered, with prescriber and pharmacist support
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Promethazine has been one of the most versatile medicines in UK pharmacy for over 75 years. As a result, it covers several quite different uses in one tablet. These include allergic conditions, nausea and motion sickness, sedation, and short-term insomnia in adults. However, modern UK practice has shifted. For most of these indications, newer alternatives offer better safety profiles. Therefore, promethazine still has a place, but in specific situations rather than as first-line treatment.
At Courier Pharmacy, we believe in treatment that fits the person.
That means being honest about where promethazine fits in modern UK practice. Furthermore, it means careful screening for the patient groups where promethazine warrants particular caution. This page covers the four main licensed uses, how promethazine compares to modern alternatives, and how to use it safely.
Five key takeaways
Promethazine 25mg Tablets is a UK Prescription-Only Medicine (POM) containing promethazine hydrochloride 25mg per tablet. It is a first-generation sedating antihistamine licensed for four main uses: allergic conditions (urticaria, allergic rhinitis, anaphylactic reactions); nausea, vomiting, and motion sickness; sedation in adults and children over 6; and short-term insomnia in adults
For most patients in 2026, modern alternatives offer better safety profiles for each indication. Non-sedating second-generation antihistamines (cetirizine, loratadine, fexofenadine, bilastine) work for allergies; ondansetron, cyclizine, or metoclopramide for nausea; CBT-I and behavioural approaches for insomnia. Therefore, promethazine is now reserved for specific clinical situations
Standard adult dose for allergic conditions: 25mg at night or 10mg to 20mg twice or three times daily, up to maximum 75mg per day. For sedation or sleep: 25mg to 50mg at night. For motion sickness: 25mg taken 1 to 2 hours before travel. The 28-tablet pack lasts 9 to 28 days depending on dose
Significant precautions apply. Specifically, promethazine is contraindicated in children under 6, in coma or CNS depression, and within 14 days of MAOI antidepressants. Furthermore, it should be avoided in older patients where safer alternatives exist, and in patients with significant respiratory disease, glaucoma, or prostate enlargement
Critical paediatric warning: promethazine must not be used in children under 2 years. The reason: serious risk of fatal respiratory depression. Furthermore, the MHRA cautions against use in children with suspected Reye’s Syndrome features. As a result, paediatric use should be coordinated with your child’s GP rather than self-supplied
Product description: Promethazine 25mg Tablets
Promethazine has been one of the most widely used medicines in UK pharmacy since the 1950s.
The compound was developed by Rhône-Poulenc as part of the phenothiazine research that also produced chlorpromazine, the first antipsychotic medicine. As a result, promethazine has structural similarity to phenothiazine antipsychotics. However, it has primarily antihistamine and sedating effects rather than antipsychotic effects.
Four licensed uses in one tablet
Promethazine 25mg Tablets are licensed in the UK for four distinct clinical uses:
Allergic conditions: symptomatic treatment of allergic conditions of the upper respiratory tract and skin, including allergic rhinitis, urticaria, and as an adjunct in anaphylactic reactions to drugs and foreign proteins
Nausea, vomiting, and motion sickness: the antiemetic and anti-motion-sickness effects make promethazine useful for short-term travel sickness and for nausea from various causes
Sedation: for both adults and children over 6, where short-term sedation is clinically appropriate
Short-term insomnia in adults: as a sedating antihistamine for sleep, typically alongside addressing underlying sleep hygiene factors
Few medicines cover this breadth of indications in one tablet. However, in modern UK practice, each indication is often better served by a more targeted alternative.
The shift away from first-generation antihistamines
Second-generation antihistamines (cetirizine, loratadine, fexofenadine, bilastine, desloratadine, levocetirizine, rupatadine) were developed to retain the histamine-blocking efficacy with substantially reduced CNS penetration. As a result, they produce equally effective allergy symptom control with much less drowsiness and far fewer anticholinergic effects.
For most UK patients with allergic conditions in 2026, the first-line choice is a non-sedating second-generation antihistamine. Furthermore, NHS, NICE, and BSACI guidance reflect this. The MHRA has issued multiple statements over the years recommending careful consideration before using first-generation sedating antihistamines.
Where promethazine still fits in modern practice
Despite the shift to newer alternatives, promethazine retains specific clinical roles:
Allergic symptoms disrupting sleep: where the sedation at bedtime is genuinely useful. For example, urticaria with night-time itching
Patients not responding adequately to non-sedating antihistamines: some patients with refractory urticaria benefit from adding or switching to a first-generation antihistamine at night
Severe acute allergic skin conditions with prominent itching: where the combination of histamine blockade plus sedation provides better symptom relief
Short-term sedation for specific situations: pre-operative anxiety, anticipated stressful events under medical guidance
Motion sickness: promethazine is one of the more effective anti-motion-sickness medicines, used either prophylactically before travel or for established motion sickness
Nausea and vomiting where ondansetron, cyclizine, or metoclopramide aren’t suitable or available
Short-term insomnia in adults: as an option when other approaches haven’t worked. However, behavioural approaches and CBT-I are first-line
How promethazine compares to other antihistamines
The UK antihistamine landscape in 2026 offers a range of options:
Second-generation non-sedating (first-line for most patients): loratadine 10mg, cetirizine 10mg, fexofenadine 180mg, bilastine 20mg, desloratadine 5mg, levocetirizine 5mg, rupatadine 10mg. Notably, these provide once-daily dosing, minimal sedation, minimal anticholinergic effects, and no significant interactions for most patients
First-generation sedating (specific situations): promethazine (Phenergan), cyproheptadine (Periactin), chlorphenamine (Piriton), hydroxyzine (Atarax), diphenhydramine (Nytol original). Used where sedation is wanted or where non-sedating options haven’t been enough
Intranasal antihistamines: azelastine (alone or as Dymista with fluticasone propionate), levocabastine. Useful for localised nasal allergic symptoms with faster onset
H2 antagonists used in allergic contexts: famotidine, nizatidine. These can be combined with H1 antihistamines for refractory urticaria
Intranasal corticosteroids: Beconase, Nasacort, Benacort, mometasone, fluticasone. Address the inflammatory component rather than blocking histamine
Leukotriene receptor antagonists: montelukast, with appropriate caution per MHRA neuropsychiatric warnings
Allergen-specific immunotherapy: Grazax, Acarizax, Itulazax for severe disease driven by specific allergens
Promethazine’s distinctive profile
Within the first-generation antihistamine class, promethazine has features that distinguish it from alternatives:
Strongest sedating profile: substantially more sedating than chlorphenamine, somewhat more than cyproheptadine. Therefore, this is most useful when sedation is wanted
Anti-emetic effects: more pronounced than other first-generation antihistamines. As a result, this makes promethazine particularly useful for motion sickness and nausea
Phenothiazine class effects: structural similarity to antipsychotics produces additional pharmacological effects but also additional precautions (QT prolongation, dystonic reactions, photosensitivity)
Long history: over 75 years of clinical use with well-characterised safety profile
Multiple indications in one tablet: useful where patients need multiple effects from one medicine
Patient groups where promethazine warrants extra caution
Several patient groups should generally avoid promethazine or use it with particular caution:
Children under 6 years: contraindicated. Promethazine carries serious respiratory depression risk in this age group, with reported fatalities particularly under age 2
Older patients (typically over 65): MHRA guidance and the Beers Criteria caution against routine sedating antihistamine use. The reasons: fall risk, cognitive impairment, urinary retention, anticholinergic burden, and CO2 retention risk. Therefore, non-sedating alternatives are strongly preferred
Patients with significant respiratory disease (COPD, severe asthma): respiratory depression risk and reduced respiratory drive
Patients with prostate enlargement: anticholinergic effects can cause urinary retention
Patients with glaucoma: anticholinergic effects can precipitate acute angle-closure
Patients with significant cardiovascular disease, particularly with QT prolongation risk or arrhythmias
Patients taking MAOI antidepressants (or within 14 days of stopping): contraindicated
Patients taking other sedating medicines: alcohol, benzodiazepines, opioid analgesics, sedating antidepressants. Cumulative sedation can be significant
Patients taking other anticholinergic medicines: amitriptyline, oxybutynin, hyoscine, some Parkinson’s disease medicines. Cumulative anticholinergic burden
Patients with cognitive impairment, dementia, or delirium: sedating antihistamines worsen cognitive function
Patients driving or operating machinery: significant impairment risk
Patients with epilepsy: theoretically lowers seizure threshold
Children with suspected Reye’s Syndrome features
We at Courier Pharmacy supply Promethazine 25mg Tablets under prescriber supervision. Our prescriber screens carefully for these considerations.
Key features and specifications
Active ingredient: promethazine hydrochloride 25mg per tablet
Form: pale blue film-coated tablet (Phenergan brand marked PN 25; generic appearance may vary)
Pack size: 28 tablets (lasts 9 to 28 days depending on indication and dose)
Licensed indications: allergic conditions (allergic rhinitis, urticaria, anaphylactic reactions); nausea, vomiting, motion sickness; sedation in adults and children over 6; short-term insomnia in adults
Standard adult dose for allergic conditions: 25mg at night, or 10mg to 20mg two to three times daily; maximum 75mg per day
Sedation/sleep dose: 25mg to 50mg at night
Motion sickness dose: 25mg taken 1 to 2 hours before travel; can repeat every 6 to 8 hours up to maximum 75mg per day
Onset of action: 20 minutes for sedating effect; 1 to 2 hours for peak antihistamine effect
Duration of effect: 4 to 6 hours for antihistamine effect; sedation can persist into the next day, particularly at higher doses
Supplied by: Courier Pharmacy, UK GPhC-registered, with prescriber and pharmacist support
Why choose Courier Pharmacy for Promethazine
At Courier Pharmacy, our approach starts with a simple idea: treatment should fit the person, not force the person to fit the system.
Dr Ada Jex-Cori
Our service is shaped by the philosophy of Dr Ada Jex-Cori, our brand pharmacist.
Dr Ada represents the spirit of the pharmacy: evidence-led, community-rooted, and willing to challenge the one-size-fits-all approach to medicine.
She is named in honour of three pioneering women in science: Ada Lovelace, the mathematician and visionary; Sophia Jex-Blake, the first female doctor in the UK who fought the medical establishment; and Gerty Cori, the biochemist and Nobel Prize winner.
In our fictional world of Ethrewell, Dr Ada fights against pharma’s standardised approach to medicine. In the real world, she represents what we stand for. Her view is straightforward: you are not broken. The system is. And we are here to change that.
Honest framing of where promethazine fits
We won’t supply promethazine routinely without consideration of whether it’s the right choice for you.
For most patients with allergic conditions, a non-sedating second-generation antihistamine is a better first choice. Furthermore, for routine sleep difficulties, behavioural approaches and CBT-I are first-line. For most causes of nausea, alternative anti-emetics are usually preferred.
Promethazine is appropriate for specific situations:
Allergic symptoms disrupting sleep, where the sedation is genuinely useful
Refractory allergic conditions where non-sedating antihistamines haven’t been enough
Motion sickness prophylaxis
Short-term insomnia after other approaches haven’t worked
Nausea where alternative anti-emetics aren’t suitable
Our prescriber will discuss your situation honestly. Furthermore, if an alternative would suit you better, we’ll say so.
Treatment that fits, not one-size-fits-all
Most online pharmacies supply promethazine without thinking through the wider picture. Courier Pharmacy is different.
We think through your situation: what symptoms you have, what you’ve already tried, what you tolerate well, what fits with your wider life including driving and work safety, and what your wider clinical picture looks like.
Promethazine may be the right answer for you. Alternatively, a non-sedating antihistamine may suit better. Furthermore, a combination approach with intranasal corticosteroid may be needed. Or specialist allergy assessment may be what’s really worth considering.
Careful screening for safety
Our prescriber screens carefully for the patient groups where promethazine warrants extra caution:
Children under 6 (contraindicated)
Older patients over 65 (alternatives strongly preferred)
Patients on MAOI antidepressants or within 14 days of stopping (contraindicated)
Patients with significant respiratory disease (COPD, severe asthma, sleep apnoea)
Patients with prostate enlargement or bladder outflow obstruction
Patients with glaucoma or family history of glaucoma
Patients on other sedating or anticholinergic medicines
Patients on QT-prolonging medicines
Patients who drive for work or operate machinery
Patients with significant medical conditions warranting prescriber assessment
If any of these apply, we’ll discuss the trade-offs and consider alternatives before supplying.
Pharmacist support before and after purchase
Our pharmacist is available to discuss:
Whether promethazine is the right medicine for your situation, or whether a non-sedating alternative would suit you better
How to take promethazine for best effect, including dosing timing to minimise daytime sedation
Managing side effects, particularly daytime drowsiness, dry mouth, and photosensitivity
Combining promethazine with other treatments like intranasal corticosteroids or H2 antagonists for refractory urticaria
Drug interactions and what to be aware of
When your situation warrants GP review, allergy testing, or specialist referral
This is free and available before and after purchase.
Care for specific patient groups
We provide tailored support for:
Patients with chronic spontaneous urticaria where standard antihistamines haven’t given full control
Patients with severe allergic skin conditions where night-time itching disrupts sleep
Patients with refractory allergic conjunctivitis alongside other symptoms
Patients needing motion sickness prophylaxis for travel
Patients with MCAS, CFS, fibromyalgia, or other long-term conditions where allergic symptoms or sleep disturbance overlap with the broader picture
Patients with multiple comorbidities and medicines where careful interaction and anticholinergic burden review is worthwhile
Coordination with your GP and other care
If you have a GP, allergist, dermatologist, sleep specialist, or other healthcare professional involved in your care, we are happy to coordinate.
Joined-up care across primary care, pharmacy, and specialist services produces better outcomes than fragmented care.
Trust earned, not claimed
We are GPhC-regulated. Furthermore, we ground our content in NHS, NICE, BNF, EMC, BSACI, and MHRA guidance.
We will tell you honestly if promethazine isn’t the right answer for your situation. We would rather give you the right advice than a quick sale.
How to buy Promethazine from Courier Pharmacy
Promethazine 25mg tablets is a Prescription Only Medicine (POM). Therefore, our prescriber issues a prescription following an online consultation. Alternatively, you can supply your own prescription from your GP or another prescriber.
How our service works
Add Promethazine 25mg Tablets to your basket and complete a brief online consultation. The consultation covers your symptoms, what you’ve already tried, current medicines, relevant medical conditions, your driving and work situation, and your alcohol intake
Our prescriber reviews your answers to confirm promethazine is suitable. If the prescriber needs additional information or wants to recommend alternatives, we will get in touch
Once approved, your prescription is dispensed and dispatched discreetly
Free pharmacist support is available before and after your purchase
When alternatives might suit better
If promethazine isn’t the right product for your situation, we will explain why. Alternatives may include:
Loratadine 10mg, cetirizine 10mg, or fexofenadine 180mg (non-sedating, over the counter) for routine allergic conditions
Bilastine 20mg, desloratadine 5mg, levocetirizine 5mg, or rupatadine 10mg (prescription, non-sedating) as alternatives
Up to fourfold standard dose of non-sedating antihistamines under prescriber guidance for refractory urticaria
Famotidine 40mg combined with H1 antihistamine for refractory chronic urticaria
Intranasal corticosteroids (Beconase, Nasacort, Benacort, mometasone, fluticasone) for allergic rhinitis with significant nasal symptoms
Dymista combination intranasal spray for severe allergic rhinitis
Cyclizine for nausea where antihistamine effect is wanted but less sedation preferred
Hyoscine hydrobromide (Kwells) for motion sickness as an alternative to promethazine
Sleep hygiene improvements and CBT-I for routine sleep difficulties before considering sedating antihistamines
Short-course melatonin for sleep difficulties, particularly in older adults
Allergen-specific immunotherapy (Grazax, Acarizax, Itulazax) for severe disease driven by specific allergens
Referral to an allergist or dermatologist for chronic, refractory, or complex allergic conditions
GP appointment if you have features warranting medical assessment
Our community service
Our free fortnightly drop-in clinics at Insomnia, Derby run every other week from 10am to 12pm.
Healthcare shouldn’t only happen when you’re paying for it. We show up, even when it’s free.
We cover allergies, hayfever, chronic urticaria, asthma, MCAS, CFS, fibromyalgia, anaphylaxis, immunotherapy, sleep difficulties, hair loss, men’s health, weight management, and whatever else people bring through the door. No appointment needed, no charge, no pressure.
Active ingredients
Each tablet contains:
Promethazine hydrochloride 25mg (active ingredient): a first-generation phenothiazine antihistamine. Notably, it has H1 receptor antagonist activity plus additional anticholinergic, anti-emetic, anti-motion-sickness, and sedating effects. Furthermore, promethazine blocks histamine at H1 receptors throughout the body. As a result, it reduces histamine-mediated symptoms. In addition, the central nervous system effects produce sedation and anti-emetic action
Excipients
Excipients commonly include:
Lactose monohydrate (173.52mg per tablet): a substantial amount; patients with severe lactose intolerance or galactose intolerance should be aware
Maize starch
Povidone
Magnesium stearate
Polyethylene glycol
Titanium dioxide (E171)
Hypromellose (E464)
Indigo carmine aluminium lake blue (E132): produces the characteristic pale blue colour
Lactose content matters
The 173.52mg of lactose per tablet is substantial. Therefore, patients with severe lactose intolerance, total lactase deficiency, or glucose-galactose malabsorption should not take this medicine.
For most patients with mild lactose sensitivity, the amount is unlikely to cause clinical problems. However, alternative antihistamines without lactose may suit better if you are highly sensitive.
Branded versus generic
Promethazine 25mg Tablets are available as branded Phenergan and as generic promethazine hydrochloride from various manufacturers. The active ingredient and clinical effect are identical. However, generic versions are typically more affordable.
Phenergan tablets are pale blue film-coated tablets marked PN 25 on one side. Generic versions may vary in appearance.
Where Promethazine fits in modern UK practice
Promethazine covers four distinct clinical areas. Furthermore, in each, modern UK practice has evolved toward newer alternatives for most patients. However, promethazine retains a place in specific situations.
Allergic conditions
Promethazine's licensed allergic indications cover three main presentations:
Allergic rhinitis (hayfever and perennial): symptoms of sneezing, itchy nose, watery rhinorrhoea, and ocular itching
Urticaria (hives): itchy raised wheals on the skin, ranging from a few isolated lesions to extensive eruption. Both acute urticaria (less than 6 weeks) and chronic spontaneous urticaria respond to antihistamines
Anaphylactic reactions to drugs and foreign proteins: as an adjunct alongside adrenaline (which is the primary life-saving treatment for anaphylaxis)
For most patients with these conditions, non-sedating second-generation antihistamines are now first-line. However, promethazine can suit:
Patients with significant night-time symptoms where the sedation is genuinely helpful
Patients with refractory urticaria not adequately controlled on non-sedating antihistamines at standard or up-to-fourfold standard doses
Patients with severe itching from acute allergic skin conditions where the combination of histamine blockade plus sedation provides better symptom relief
Anaphylaxis is not an antihistamine indication
Despite its licensed indication as an adjunct in anaphylactic reactions, promethazine is not a treatment for anaphylaxis.
Anaphylaxis is a medical emergency requiring intramuscular adrenaline as the first-line life-saving intervention. Antihistamines (sedating or non-sedating) should never delay adrenaline. Therefore, patients with known anaphylaxis risk should carry adrenaline autoinjectors (EpiPen, Jext, or Eurneffy nasal adrenaline).
Promethazine's role as an adjunct in anaphylactic reactions is limited to supporting management once adrenaline has been given and the patient is in a safe clinical setting.
Nausea, vomiting, and motion sickness
Promethazine has substantial anti-emetic and anti-motion-sickness effects. As a result, it is one of the more effective options in this category.
Clinical uses include:
Motion sickness prophylaxis (travel sickness): take 1 to 2 hours before travel for best effect. Furthermore, this approach generally works better than taking promethazine after motion sickness has started
Treatment of established motion sickness once symptoms are present
Nausea and vomiting from various causes: pregnancy-related nausea (under specialist guidance), vestibular disorders, post-operative nausea, drug-induced nausea where ondansetron and metoclopramide aren't suitable
However, modern UK practice prefers other anti-emetics for most causes of nausea:
Ondansetron: serotonin antagonist, very effective for chemotherapy and post-operative nausea
Metoclopramide: dopamine antagonist, useful for nausea associated with delayed gastric emptying
Cyclizine: another first-generation antihistamine with anti-emetic effect, often preferred where antihistamine effect is wanted
Prochlorperazine (Buccastem): phenothiazine class with anti-emetic effect, available as buccal tablets useful when oral intake is impaired
Hyoscine hydrobromide (Kwells, scopolamine): the most established anti-motion-sickness option, available as tablets or patches
Promethazine's place is for patients where other options aren't suitable, or for motion sickness where its sedating profile is acceptable.
Sedation
Promethazine has strong sedating effects, more pronounced than most other first-generation antihistamines.
Clinical uses for sedation include:
Pre-operative anxiety reduction (in hospital settings)
Anticipated stressful events under medical guidance
Short-term sedation in children over 6 years where clinically appropriate (typically under paediatric specialist guidance)
The strong sedating effect is also the limiting factor for routine antihistamine use. Therefore, where sedation is unwanted, a non-sedating antihistamine should be the first choice.
Short-term insomnia in adults
Promethazine is licensed for short-term insomnia in adults.
However, NICE guidance and most sleep medicine practice consider it a third-line or fourth-line option. The hierarchy in modern UK practice:
First-line: sleep hygiene improvements (consistent sleep schedule, dark cool bedroom, no screens before bed, no caffeine in afternoon, regular exercise)
Second-line: cognitive behavioural therapy for insomnia (CBT-I), available through online programs (Sleepio, Sleep Station) or face-to-face therapy
Third-line for specific patients: short-course melatonin (particularly for older adults or where circadian rhythm is involved); short-course Z-drugs (zopiclone, zolpidem) or short-acting benzodiazepines under careful prescribing
Sedating antihistamines including promethazine: an option where other approaches haven't worked, but not first-line
Tolerance to the sedating effect develops with regular use of promethazine. As a result, this can lead to dose escalation and rebound insomnia on stopping. Therefore, short-course use is appropriate; long-term use is not.
Where Courier Pharmacy positions promethazine
We supply promethazine for patients in specific clinical situations:
Allergic conditions where sedation is genuinely useful (night-time urticaria, severe itching)
Refractory urticaria not adequately controlled by non-sedating antihistamines
Motion sickness prophylaxis
Short-term insomnia in adults after other approaches haven't worked
Nausea and vomiting where alternatives aren't suitable
For patients with routine allergic conditions, mild sleep difficulties, or occasional nausea, we'll discuss whether a different approach would suit better. The right answer depends on your specific situation.
How promethazine works
Promethazine has multiple mechanisms of action. As a result, these contribute to its therapeutic and side effect profile.
H1 histamine receptor antagonism
The primary therapeutic effect for allergic conditions. Promethazine competitively blocks histamine binding to H1 receptors throughout the body.
This reduces the typical histamine-mediated symptoms of allergic reactions:
Itching, sneezing, watery eyes, rhinorrhoea
Urticaria and angioedema
Capillary leak and oedema in allergic responses
Central nervous system effects
Promethazine readily crosses the blood-brain barrier. As a result, it produces significant CNS effects:
Sedation through central H1 receptor blockade and additional CNS receptor effects
Anti-emetic effect through blockade of histamine and dopamine receptors in the vomiting centre and chemoreceptor trigger zone
Anti-motion-sickness effect through additional vestibular system effects
Anti-cholinergic effect on cognitive function
Anticholinergic effects
Promethazine has substantial muscarinic acetylcholine receptor antagonist activity. As a result, this contributes to:
Drying of secretions (the basis for some uses, but also causes dry mouth)
Mild bronchodilation
Urinary retention (problem in patients with prostate enlargement)
Blurred vision (from pupil dilation and reduced lens accommodation)
Constipation
Cognitive effects (confusion, particularly in older patients)
The anticholinergic effects are a significant reason why second-generation antihistamines (with much less anticholinergic activity) are preferred for routine allergy care.
Additional phenothiazine class effects
Promethazine is structurally a phenothiazine, related to antipsychotic medicines. As a result, it has additional pharmacological effects:
Alpha-adrenergic antagonism: can cause orthostatic hypotension
Dopamine receptor antagonism (mild): contributes to anti-emetic effect but rarely also produces extrapyramidal effects
Effects on cardiac repolarisation: QT prolongation potential at higher doses or with predisposing factors
Photosensitivity: increased skin sensitivity to sunlight, sometimes producing severe sunburn
Pharmacokinetics
After oral administration, promethazine is well-absorbed from the GI tract. Peak plasma concentrations occur 1 to 3 hours after dosing.
The half-life is around 10 to 14 hours. Therefore, this allows once-daily dosing for sustained allergic condition control. However, the antihistamine effect is shorter than the half-life suggests (around 4 to 6 hours), while the sedating effect can persist into the next day.
Metabolism is primarily hepatic via CYP2D6 and other enzymes. Notably, promethazine is a moderate inhibitor of CYP2D6 itself. As a result, this creates a number of clinically relevant drug interactions.
How to take Promethazine 25mg tablets
This summary is for reference only. The definitive guide is the patient information leaflet supplied with the product. If you are uncertain about any aspect of dosing, contact our pharmacist for support.
Adult dosing for allergic conditions
Standard dose: 25mg taken at night, or 10mg to 20mg two to three times daily
Maximum daily dose: 75mg per day
Many patients find a single 25mg dose at night provides good control while limiting daytime sedation
Adult dosing for sedation and short-term insomnia
25mg to 50mg as a single dose at bedtime
Use for short courses only (typically 7 to 10 days) to avoid tolerance and dependence patterns
Combine with sleep hygiene improvements and consider CBT-I for sustained benefit
Adult dosing for motion sickness
25mg taken 1 to 2 hours before travel
Can repeat every 6 to 8 hours during travel; maximum 75mg per day
Taking before symptoms develop generally works better than taking after motion sickness has started
Adult dosing for nausea and vomiting
25mg taken at the start of nausea symptoms
Can repeat every 6 to 8 hours; maximum 75mg per day
Older patients
Promethazine is generally not recommended for patients over 65 because of fall risk, cognitive effects, and anticholinergic burden.
Where promethazine is judged the right choice despite these concerns, start at lower doses (12.5mg, half a tablet) and titrate carefully. Furthermore, non-sedating alternatives are strongly preferred in this age group.
Children
Critical age restrictions:
Children under 2 years: absolutely contraindicated. Serious risk of fatal respiratory depression, with reported deaths
Children under 6 years: not for use in this age group at all
Children 6 years and over: paediatric dosing depends on indication and weight; should be prescribed by a paediatrician or GP rather than self-supplied
Furthermore, promethazine should be avoided in children with suspected Reye's Syndrome features.
Pregnancy and breastfeeding
Pregnancy: limited human data. Manufacturer advises against use in pregnancy unless considered essential by the prescriber.
For allergic conditions in pregnancy, loratadine and cetirizine have more extensive safety data and are preferred. For pregnancy-related nausea, alternative anti-emetics (cyclizine, prochlorperazine, ondansetron) have more established pregnancy safety profiles.
Breastfeeding: promethazine is excreted in breast milk and can cause sedation, irritability, and feeding effects in the infant. As a result, it is not recommended during breastfeeding.
How to take
Swallow the tablet whole with a glass of water
Can be taken with or without food; food doesn't significantly affect absorption
Time doses to suit your symptom pattern: bedtime dose for night-time symptoms or sleep; daytime doses spread across the day for sustained allergy control
Tablets can be split if needed for half-dose titration (12.5mg)
When to expect results
Sedating effect begins within 20 to 30 minutes. Therefore, take 30 to 60 minutes before bedtime for sleep effect.
Peak antihistamine effect occurs at 1 to 2 hours; duration of antihistamine effect is 4 to 6 hours. However, sedation can persist for 6 to 12 hours at standard doses.
How long to take
Duration depends on indication:
Acute allergic reactions: short course of a few days
Seasonal allergic rhinitis: through the dominant pollen season
Chronic urticaria: longer-term use with periodic prescriber review; consider whether switching to non-sedating antihistamine would now suit
Motion sickness: single dose before travel or short course during travel
Sedation/insomnia: short courses only (7 to 10 days typically) to avoid tolerance and dependence
Nausea and vomiting: short course addressing the underlying cause
Missing a dose
If you miss a dose, take it as soon as you remember. However, skip the missed dose if it's nearly time for the next one. Don't double-dose to catch up.
Stopping promethazine
Promethazine can be stopped without a taper after short-course use. However, after prolonged use for insomnia, you may experience rebound insomnia for a few nights. This typically settles within 1 to 2 weeks.
For chronic urticaria use, symptoms of the underlying condition will return if promethazine was effectively controlling them.
Storage
Store at room temperature, below 25°C, in the original packaging to protect from moisture and light. Keep out of sight and reach of children.
Warnings and precautions for Promethazine
Absolute contraindications
Promethazine must not be used in:
Children under 2 years of age (with under 2 years carrying serious respiratory depression risk and reported fatalities)
Patients with known hypersensitivity to promethazine, other phenothiazines, or any tablet excipient
Patients in coma or suffering from CNS depression of any cause
Patients taking monoamine oxidase inhibitors (MAOIs) or within 14 days of stopping MAOIs
Patients with severe lactose intolerance, total lactase deficiency, or glucose-galactose malabsorption (because of the lactose content)
Breastfeeding women
Critical paediatric warning
The MHRA has issued specific warnings about promethazine in young children. Critical points:
Under 2 years: absolutely contraindicated. Reported fatalities from respiratory depression
Children with suspected Reye's Syndrome features: avoid because of risk of worsening the condition
Older patients
MHRA guidance and the Beers Criteria (an international list of medicines best avoided in older patients) advise against routine use of first-generation sedating antihistamines including promethazine in patients over 65.
The reasons:
Increased fall risk from sedation and dizziness
Cognitive impairment, particularly in patients with dementia or delirium risk
Urinary retention with prostate enlargement
Worsening of glaucoma
Cumulative anticholinergic burden contributing to longer-term cognitive decline
Driving safety concerns
CO2 retention risk in patients with chronic respiratory disease
For older patients with allergic conditions, non-sedating second-generation antihistamines (cetirizine, loratadine, fexofenadine) are strongly preferred.
Driving and operating machinery
Promethazine causes significant sedation in most patients.
The MHRA has issued specific guidance on driving with sedating medicines. Patients on promethazine should:
Not drive or operate machinery until they know how the medicine affects them personally
Avoid driving if they experience any drowsiness, slowed reactions, or impaired concentration
Be aware that the legal drug-driving regulations in the UK include certain medicines; impairment from prescribed medicines can still result in driving offences
Be aware that sedation can persist into the next day, particularly after evening doses
Consider non-sedating alternatives if regular driving is essential
If you have a job that involves driving (lorry, taxi, bus), operating machinery, working at heights, or other safety-critical roles, discuss this with our prescriber. Furthermore, a non-sedating antihistamine is likely to be a better choice.
Alcohol and other sedating substances
Avoid alcohol while taking promethazine. The combined sedation can be substantial and dangerous.
Other sedating antihistamines (cyproheptadine, chlorphenamine, diphenhydramine, hydroxyzine)
Combination of promethazine with these substances substantially increases sedation, impaired coordination, respiratory depression risk (particularly with opioids), and accident risk.
Respiratory disease
Promethazine should be used with caution in patients with significant respiratory disease. Specifically:
COPD: risk of CO2 retention from reduced respiratory drive
Severe asthma: theoretical risk of bronchospasm from histamine receptor effects
Sleep apnoea: worsening of respiratory depression during sleep
Acute respiratory infection: caution in patients with reduced respiratory reserve
Anticholinergic burden
Promethazine contributes significantly to overall anticholinergic burden. Furthermore, high anticholinergic burden is associated with:
Confusion and cognitive impairment, particularly in older patients
Increased dementia risk with long-term use
Urinary retention
Constipation
Falls
Hospital admissions in vulnerable patients
Patients already on anticholinergic medicines (amitriptyline, nortriptyline, oxybutynin, tolterodine, hyoscine, some Parkinson's disease medicines, some antipsychotics) should generally avoid adding promethazine. Therefore, non-sedating antihistamines are a better choice for cumulative burden reasons.
Photosensitivity
Promethazine, like other phenothiazines, can cause significant photosensitivity. As a result, skin becomes more sensitive to ultraviolet light, sometimes producing severe sunburn or skin reactions with relatively low sun exposure.
Patients taking promethazine should:
Use high-factor sunscreen (SPF 30 to 50)
Wear protective clothing in strong sun
Avoid prolonged sun exposure during peak UV hours
Be aware that the photosensitivity can persist for several days after stopping promethazine
QT prolongation
Promethazine can prolong the QT interval at higher doses or in patients with predisposing factors. As a result, this increases the risk of torsades de pointes arrhythmia.
Special caution is required when combining promethazine with other QT-prolonging medicines:
Some antiarrhythmics (amiodarone, sotalol)
Some antimicrobials (macrolides, fluoroquinolones, antimalarials)
Some antidepressants (citalopram, escitalopram at higher doses)
Some antipsychotics
Pregnancy and breastfeeding
Pregnancy: limited human data. Avoid use in pregnancy unless considered essential by the prescriber.
Loratadine and cetirizine have more extensive pregnancy safety data and are preferred for allergic conditions in pregnancy. For pregnancy-related nausea, cyclizine, prochlorperazine, and ondansetron are alternatives with more established pregnancy use.
Breastfeeding: not recommended. Promethazine is excreted in breast milk and can cause sedation, irritability, and feeding effects in the infant.
Surgery and anaesthesia
Stop promethazine at least 72 hours before any allergy testing because it interferes with skin prick test results.
For surgery, mention promethazine use to the anaesthetist. The medicine can interact with anaesthetic agents and contribute to anticholinergic effects.
Side effects of Promethazine
Promethazine has a more extensive side effect profile than newer non-sedating antihistamines. The reasons: its sedating, anticholinergic, and phenothiazine-class effects.
Very common side effects (more than 1 in 10 patients)
Sedation, drowsiness, fatigue (the most common and limiting side effect; particularly pronounced at the start of treatment)
Dry mouth
Common side effects (up to 1 in 10 patients)
Dizziness
Impaired concentration and slowed reaction time
Headache
Blurred vision
Constipation
Urinary retention or difficulty starting urination
Hangover effect into the next day after evening doses
Nausea (paradoxical, though promethazine is also used for nausea)
Restlessness or agitation (paradoxical, particularly in children and older patients)
Less common side effects
Confusion, particularly in older patients
Insomnia or sleep disturbance (paradoxical, more common in children)
Tremor
Skin rash
Photosensitivity (significant sun sensitivity, sometimes producing severe sunburn)
Hypotension and dizziness on standing
Palpitations
Tinnitus
Rare but more significant side effects
Severe hypersensitivity reactions including anaphylaxis (very rare)
Hepatic dysfunction with jaundice or significant abnormal liver function tests
Blood dyscrasias (rare reports of leucopenia, agranulocytosis, thrombocytopenia)
Seizures (very rare)
Significant cardiovascular effects including QT prolongation, arrhythmias, and significant hypotension
Extrapyramidal effects: dystonic reactions, tardive dyskinesia (rare with promethazine; more associated with antipsychotic-dose phenothiazines)
Neuroleptic malignant syndrome (very rare)
Severe anticholinergic syndrome (overdose or excessive cumulative anticholinergic burden)
Acute angle-closure glaucoma in susceptible patients
Severe respiratory depression (particularly in children and patients with respiratory disease)
Stop and seek advice if
You develop severe drowsiness affecting safety or daily functioning
You develop significant urinary retention (cannot pass urine, severe lower abdominal discomfort)
You develop new visual symptoms (sudden blurring, eye pain, halos around lights; possible angle-closure glaucoma)
You develop significant confusion, particularly in an older patient
You develop signs of severe allergic reaction (significant swelling, difficulty breathing, severe rash)
You develop jaundice (yellowing of skin or eyes), persistent significant nausea, or right upper abdominal pain
You develop persistent headache, dizziness, or symptoms affecting your ability to drive safely
You develop unexplained bruising, bleeding, or frequent infections (possible blood dyscrasia)
You develop irregular heartbeats, fainting, or palpitations (possible QT prolongation)
You develop severe sunburn with relatively low sun exposure (photosensitivity)
You develop muscle stiffness, fever, confusion, and sweating (possible neuroleptic malignant syndrome; very rare but medical emergency)
Yellow Card reporting
You can report suspected adverse drug reactions to the MHRA via the Yellow Card scheme at yellowcard.mhra.gov.uk. Reporting helps build the safety picture for everyone.
Drug interactions with Promethazine
Promethazine has multiple clinically significant interactions. Our pharmacist checks the picture during your consultation.
Absolute contraindications (do not combine)
Monoamine oxidase inhibitors (MAOIs): phenelzine, tranylcypromine, isocarboxazid, moclobemide. Concurrent use is contraindicated. Prolonged and intensified anticholinergic effects, severe hypotension, and other significant effects can occur. Wait at least 14 days after stopping MAOI before starting promethazine
Significant interactions requiring care
Alcohol: significant additive sedation; avoid alcohol while taking promethazine
CYP2D6 substrates: promethazine is a moderate inhibitor of CYP2D6. As a result, it can increase the plasma concentrations of medicines metabolised by this enzyme. Notable substrates include tricyclic antidepressants (amitriptyline, nortriptyline), some beta-blockers (metoprolol), some antiarrhythmics, codeine, tramadol
QT-prolonging medicines: some antiarrhythmics (amiodarone, sotalol), some antimicrobials (macrolides, fluoroquinolones, antimalarials), some antidepressants (citalopram, escitalopram), some antipsychotics. Increased risk of QT prolongation and torsades de pointes
Allergy testing (skin prick tests, intradermal tests): stop promethazine at least 72 hours before testing to avoid false-negative results
Less significant interactions
Antihypertensives: theoretical reduction in antihypertensive effect; usually not clinically significant
Phenytoin and other antiepileptics: theoretical seizure threshold lowering; usually not clinically significant at standard doses
Anticoagulants (warfarin, DOACs): no significant pharmacokinetic interaction, but sedation may mask early signs of bleeding
Not significant interactions
Most other antibiotics not in the QT-prolonging or CYP2D6-interacting categories
Most blood pressure medicines, statins, hormonal contraceptives at standard doses
PPIs and H2 antagonists: no significant interaction
Intranasal corticosteroids and other allergy medicines: compatible with promethazine
For patients on multiple medicines, particularly sedating, anticholinergic, antidepressant, antipsychotic, or QT-prolonging medicines, our prescriber will check the picture carefully before supplying promethazine.
Frequently asked questions about Promethazine
What is Promethazine used for?
Promethazine 25mg Tablets is licensed in the UK for four main uses: allergic conditions (allergic rhinitis, urticaria, anaphylactic reactions as adjunct); nausea, vomiting, and motion sickness; sedation in adults and children over 6; and short-term insomnia in adults.
Is Promethazine the same as Phenergan?
Yes. Phenergan is the originator brand name. Generic Promethazine 25mg Tablets contain the same active ingredient at the same dose. The clinical effects are identical.
Why is Promethazine a prescription medicine?
Promethazine is a first-generation sedating antihistamine with significant side effects and interactions. Substantial sedation, anticholinergic effects, photosensitivity, and contraindications in several patient groups mean prescriber supervision is appropriate. Furthermore, the paediatric warnings (no use under 6 years; contraindication under 2 years) are critical safety considerations.
How is Promethazine different from non-sedating antihistamines?
Non-sedating second-generation antihistamines (cetirizine, loratadine, fexofenadine, bilastine) block the same H1 histamine receptors as promethazine. However, they don't cross the blood-brain barrier significantly.
As a result, they provide equal efficacy for histamine-mediated symptoms with much less sedation and far fewer anticholinergic effects. For most patients, these newer antihistamines are a better first choice.
When would I want a sedating antihistamine like Promethazine?
Specific situations:
Allergic symptoms disrupting your sleep, where bedtime sedation is wanted
Refractory urticaria or other allergic conditions not responding adequately to non-sedating antihistamines
Severe itching from acute allergic skin conditions
Motion sickness prophylaxis
Short-term insomnia after other approaches haven't worked
Nausea and vomiting where alternative anti-emetics aren't suitable
For routine seasonal hayfever or mild allergic conditions, a non-sedating option is usually better.
How quickly does Promethazine work?
Sedating effect begins within 20 to 30 minutes. Peak antihistamine effect occurs at 1 to 2 hours. Duration of antihistamine effect is 4 to 6 hours; sedation can persist for 6 to 12 hours.
Can I drive while taking Promethazine?
Not until you know how the medicine affects you personally. Promethazine causes significant sedation in most patients.
If you experience any drowsiness, slowed reactions, or impaired concentration, don't drive. The legal drug-driving regulations in the UK include certain medicines; impairment from prescribed medicines can still result in driving offences.
Furthermore, sedation can persist into the next day after evening doses. For patients who drive for work, a non-sedating alternative is strongly preferred.
Can I drink alcohol while taking Promethazine?
Avoid alcohol while taking promethazine. The combination produces substantial additive sedation that can be dangerous.
Can older patients take Promethazine?
Generally not recommended. MHRA guidance and the Beers Criteria advise against routine sedating antihistamine use in patients over 65 because of fall risk, cognitive effects, urinary retention with prostate enlargement, glaucoma worsening, and cumulative anticholinergic burden. Non-sedating alternatives are strongly preferred.
Can I take Promethazine during pregnancy?
Limited human data. Manufacturer advises against use in pregnancy unless considered essential by the prescriber.
Loratadine and cetirizine have more extensive pregnancy safety data and are preferred for allergic conditions in pregnancy. For pregnancy-related nausea, cyclizine, prochlorperazine, and ondansetron have more established pregnancy use.
Can I take Promethazine while breastfeeding?
No, not recommended. Promethazine is excreted in breast milk and can cause sedation, irritability, and feeding effects in the infant. Loratadine and cetirizine are considered safer during breastfeeding.
Can children take Promethazine?
Children under 6 years: not for use at all.
Children under 2 years: absolutely contraindicated because of fatal respiratory depression risk.
Children 6 and over: paediatric use should be coordinated with the child's GP or paediatrician rather than self-supplied through online pharmacy.
Does Promethazine help me sleep?
Yes, promethazine has strong sedating effects and is licensed for short-term insomnia in adults. However, NICE guidance considers sedating antihistamines a third-line or fourth-line sleep option.
First-line is sleep hygiene improvements and CBT-I. Furthermore, tolerance to the sedating effect develops with regular use, which can lead to dose escalation and rebound insomnia on stopping. Therefore, use promethazine for sleep in short courses only.
Does Promethazine help with motion sickness?
Yes, promethazine is effective for motion sickness, particularly when taken 1 to 2 hours before travel. Hyoscine hydrobromide (Kwells) is an alternative that some patients prefer because of less sedation.
Can I take Promethazine with my other allergy medicines?
Promethazine is compatible with intranasal corticosteroids (Beconase, Nasacort, Benacort, mometasone, fluticasone), H2 antagonists (famotidine), and most other allergy treatments. The combination of promethazine with H1 plus famotidine H2 antagonist is sometimes used for refractory urticaria.
However, avoid combining promethazine with other sedating antihistamines (cyproheptadine, chlorphenamine, diphenhydramine, hydroxyzine) because of additive sedation.
How long can I take Promethazine for?
Duration depends on the condition. For acute allergic reactions: a few days. For chronic urticaria: longer-term use under prescriber review. For motion sickness: single dose or short course around travel. For sleep: short courses only (7 to 10 days typically).
Periodic prescriber review is sensible for long-term use to confirm ongoing benefit and consider whether a non-sedating alternative would now suit better.
What if Promethazine makes me too sleepy the next day?
Common after evening doses. Options:
Take earlier in the evening (around 7 to 8pm rather than just before bed)
Reduce to a lower dose (half a tablet, 12.5mg)
Take with food
Consider switching to a non-sedating alternative
Discuss with our pharmacist or prescriber.
Does Promethazine cause weight gain?
Some patients gain weight on promethazine, related to increased appetite from the antihistamine effects and possibly to sedation reducing physical activity. Weight gain is usually modest at standard doses but can be more significant at higher doses or with prolonged use.
Why do I need to avoid sun while taking Promethazine?
Promethazine, like other phenothiazines, can cause significant photosensitivity. Your skin becomes more sensitive to ultraviolet light, sometimes producing severe sunburn with relatively low sun exposure.
Use high-factor sunscreen, wear protective clothing, and avoid prolonged sun exposure during peak UV hours.
Can I stop Promethazine suddenly?
After short-course use, yes. After prolonged use for insomnia, you may experience rebound insomnia for a few nights. This typically settles within 1 to 2 weeks.
For chronic urticaria use, symptoms of the underlying condition will return if promethazine was effectively controlling them.
How should I store Promethazine?
Store at room temperature, below 25°C, in the original packaging to protect from moisture and light. Keep out of sight and reach of children.
How do I order Promethazine from Courier Pharmacy?
Add the product to your basket on courierpharmacy.co.uk and complete the online consultation. Our prescriber will review your answers and confirm suitability.
If you already have a prescription from another prescriber, you can supply that. Free pharmacist support is available before and after your order.
More than a prescription: our community
Healthcare shouldn't only happen when you're paying for it.
Every fortnight we run free drop-in talks and clinics at Insomnia, Derby, from 10am to 12pm. We show up, even when it's free.
Bring a question, bring a friend, bring a stack of bewildering letters from another clinic. We'll sit with you.
We cover allergies, hayfever, chronic urticaria, asthma, MCAS, CFS, fibromyalgia, anaphylaxis, immunotherapy, sleep difficulties, hair loss, men's health, weight management, and whatever else people bring through the door. No appointment. No cost. No pressure. Just real support and treatment that fits.
Disclaimer: This article is for information only and isn't a substitute for personal medical advice. Always speak to a qualified prescriber before starting or changing treatment.
How this content was created
Written by the Courier Pharmacy editorial team and reviewed by a GPhC-registered pharmacist.
The content is grounded in the latest NHS, BNF, and EMC guidance. Furthermore, it draws on the real questions patients bring to our drop-in clinics in Derby.
