Home » Treatment » Viridal Duo 10mcg injections (alprostadil)
Viridal Duo 10mcg injections (alprostadil)
from£64.99
Viridal Duo is a UK Prescription Only Medicine and a dual-chamber injection system delivering alprostadil (synthetic prostaglandin E1) for intracavernosal self-injection in the treatment of erectile dysfunction.
Onset is within 5 to 20 minutes and duration is around 30 to 60 minutes.
Courier Pharmacy supplies Viridal Duo as a continuation service for men already established on the medicine through an NHS urology service, private men’s health clinic, or other appropriate specialist pathway.
Viridal Duo is a UK Prescription Only Medicine (POM) for erectile dysfunction (ED). It contains alprostadil, which is a man?made version of a natural body chemical called prostaglandin E1.
It comes in a dual?chamber injection system. One chamber holds the dry powder. The other holds the liquid. You mix them just before use, then inject the solution into the penis (intracavernosal injection).
Most men get an erection in 5 to 20 minutes. The effect often lasts 30 to 60 minutes, depending on the dose and the person.
How Viridal Duo works (in plain English)
Alprostadil helps the blood vessels in the penis open up. This increases blood flow and helps the erectile tissue fill and stay firm.
This erection does not rely on sexual stimulation. That is different from tablets like sildenafil or tadalafil, which usually need arousal to work.
Why the injection route matters
Viridal Duo delivers the medicine directly to where it needs to work. It does not go through the gut first. It also avoids “first?pass” breakdown in the liver.
This is one reason it can help when ED tablets have not worked well. For example, it may help some men:
after prostate surgery
with diabetes?related nerve damage
with spinal cord injury
with more severe blood?flow related ED
Where Viridal Duo fits in ED treatment
Clinicians often treat ED in steps. Viridal Duo usually sits as a second?line option.
A typical stepped approach is:
First line: lifestyle changes and oral ED tablets
Second line: injection therapy (like alprostadil), vacuum devices, or intraurethral alprostadil
Third line: penile implant surgery
Viridal Duo can be useful if you:
cannot take ED tablets (for example, because you use nitrates)
did not get a good response from tablets
have a clinical reason injection therapy may work better
Viridal Duo at Courier Pharmacy (continuation service)
Courier Pharmacy supplies Viridal Duo as a continuation service. This means you should already have been started on it through an appropriate clinical pathway.
Our online consultation checks:
that you have been initiated on Viridal Duo (or alprostadil injection therapy)
your current dose and how you use it
your prescriber involvement and follow?up plan
If you want to start Viridal Duo for the first time, we can explain the usual initiation pathway and point you to the right service.
Key features and specifications
Active ingredient: alprostadil (synthetic prostaglandin E1)
Form: dual?chamber system; powder and solvent mixed before injection
Common strengths in UK practice: 10 micrograms (mcg), 20mcg, 40mcg
Pack size: often 5 syringes per pack (strength?specific)
Indication: erectile dysfunction in adult men (various causes)
Onset: usually 5 to 20 minutes
Duration: often 30 to 60 minutes
Maximum frequency: no more than 1 injection in 24 hours, and no more than 3 injections per week
Dose: personalised and set by titration (often 5mcg to 40mcg)
Legal category: Prescription Only Medicine (POM)
Supply route: UK GPhC?registered pharmacy, continuation after initiation elsewhere
Safety note (important)
Viridal Duo is not suitable for everyone. Use it only as prescribed. Do not increase your dose or frequency on your own.
Speak to a clinician urgently if you have:
an erection lasting longer than expected (especially over 4 hours)
What is Viridal Duo (Alprostadil Intracavernosal Injection)?
When oral erectile dysfunction medicines (sildenafil, tadalafil, vardenafil, avanafil) haven’t worked, can’t be taken because of nitrate use or other contraindications, or aren’t a clinical fit for your situation, intracavernosal injection therapy is one of the established next-line options. Viridal Duo is the UK-licensed alprostadil dual-chamber injection system used by men whose erectile dysfunction has been assessed clinically and who have been initiated on injection therapy under appropriate medical supervision.
At Courier Pharmacy, we believe healthcare should suit the person, not the marketing budget. This page is here for men who have already been started on Viridal Duo through a urology clinic, men’s health service, or specialist prescriber, and who are looking for a reliable continuation supply with ongoing pharmacist support. Whether you’re managing erectile dysfunction following prostate surgery, after spinal cord injury, due to diabetes-related nerve and vessel changes, or where oral medicines have not been right for you, this page covers what Viridal Duo is, how it works, and how we can support your ongoing use.
Important note: continuation supply, not initiation
Viridal Duo is not a medicine we initiate through remote online consultation. First-dose titration needs to happen under direct medical supervision because of the risk of prolonged erection (priapism), the need for hands-on injection technique training, and the dose individualisation that depends on your clinical observation and response. Initial assessment and first-dose administration should take place at an NHS urology clinic, a private men’s health service, or with a prescriber experienced in intracavernosal injection therapy who can observe the first administration.
We supply Viridal Duo as a continuation service for men who have already completed this initiation process elsewhere, have an established maintenance dose, and need ongoing supply with the support of a UK GPhC-registered pharmacy. The online consultation will confirm your initiation history, your current maintenance dose, the prescriber who initiated you, and any ongoing clinical follow-up. If you have not yet been initiated, we will explain the pathway and signpost appropriate services.
Five key takeaways
Viridal Duo is a UK Prescription Only Medicine containing alprostadil (synthetic prostaglandin E1), delivered as a dual-chamber injection system for direct intracavernosal injection into the corpus cavernosum of the penis to produce an erection.
The medicine is licensed for erectile dysfunction of neurogenic, vasculogenic, psychogenic, or mixed aetiology in adult men. It is typically used when oral PDE5 inhibitors (sildenafil, tadalafil, vardenafil, avanafil) have been ineffective, contraindicated, or not a clinical fit.
Available strengths in UK practice are typically 10mcg, 20mcg, and 40mcg per dose, with starter packs containing mixed strengths for titration. Maintenance dose is individualised after clinical initiation, and most patients settle on a dose between 5mcg and 40mcg per injection.
First-dose titration and injection technique training need to happen under direct medical supervision in a clinic, urology service, or with a prescriber experienced in intracavernosal injection therapy. Courier Pharmacy supplies Viridal Duo as a continuation service, not for first-time initiation.
The most clinically important risk is priapism (prolonged erection lasting more than 4 hours), which is a urological emergency. Patients on Viridal Duo need clear emergency planning and rapid access to urology care if priapism develops.
The clinical context: where Viridal Duo fits
Erectile dysfunction in adult men is common, affecting around 40 to 50% of men over 40 to varying degrees, with prevalence increasing with age. The underlying causes are typically a mix of cardiovascular (atherosclerosis affecting the small arteries supplying the corpus cavernosum), neurological (diabetic neuropathy, post-surgical nerve damage, spinal cord injury, multiple sclerosis, Parkinson’s disease), endocrine (low testosterone, thyroid dysfunction, hyperprolactinaemia), psychological (anxiety, depression, relationship factors, performance concerns), and pharmacological (antihypertensives, antidepressants, finasteride, some psychiatric medicines, recreational substance use).
The first-line pharmacological treatment for erectile dysfunction in most clinical settings is an oral PDE5 inhibitor: sildenafil (Viagra), tadalafil (Cialis), vardenafil (Levitra), or avanafil (Spedra). These medicines work by inhibiting phosphodiesterase type 5, the enzyme that breaks down cyclic GMP in the corpus cavernosum. With PDE5 inhibited, cGMP builds up in response to sexual stimulation (which triggers nitric oxide release), and the smooth muscle of the corpus cavernosum relaxes, allowing blood flow and erection.
For around 70% of men with erectile dysfunction, oral PDE5 inhibitors at appropriate doses produce a satisfactory response. For the remaining 30%, the response is inadequate, the medicines are not tolerated, or there are contraindications that prevent their use. This group includes:
Men taking nitrate medicines (GTN sprays or tablets for angina, isosorbide mononitrate, isosorbide dinitrate). The combination of nitrate and PDE5 inhibitor produces dangerous hypotension and is absolutely contraindicated.
Men with severe cardiovascular disease where the haemodynamic effects of PDE5 inhibitors are not acceptable.
Men after radical prostatectomy where the cavernous nerves have been damaged or removed, particularly in non-nerve-sparing procedures. The nitric oxide / cGMP pathway depends on intact neural input, which oral PDE5 inhibitors cannot restore.
Men with severe diabetic neuropathy affecting the cavernous nerves.
Men with spinal cord injury affecting the relevant neural pathways.
Men with anatomical or vascular changes that prevent adequate response to oral medicines.
Men who cannot tolerate the side effects of PDE5 inhibitors (headache, flushing, nasal congestion, dyspepsia, visual changes).
For this group, intracavernosal injection therapy with alprostadil is one of the most established next-line options. Intracavernosal alprostadil produces an erection without requiring an intact nitric oxide / cGMP pathway and without requiring sexual stimulation. The mechanism is independent of the neural pathways that oral PDE5 inhibitors depend on, which is why injection therapy often works when oral medicines do not.
Alternatives within the second-line space include intraurethral alprostadil (MUSE), which is a small pellet inserted into the urethra rather than an injection; combination intracavernosal injections (alprostadil with papaverine and/or phentolamine, sometimes called “trimix” or “bimix”, typically prepared as specials by compounding pharmacies); and non-pharmacological options including vacuum erection devices. Each has a place; the choice between them depends on the patient’s preferences, anatomy, ability to use the device, partner involvement, and clinical response.
Intracavernosal injection therapy is not the right answer for every man. It requires confidence with self-injection, an anatomical site that can be reliably injected, partner acceptance in many cases, and willingness to engage with the safety considerations including priapism risk. For men who do engage with the technique, response rates are typically in the 70 to 90% range for satisfactory erection, which is higher than oral PDE5 inhibitor response rates in selected populations.
Why initiation needs in-person supervision
The reasons we will not initiate Viridal Duo through remote online consultation are worth setting out clearly, because they are clinical rather than administrative.
First-dose response is unpredictable
The right dose for a given man cannot be determined in advance from clinical history alone. Men with similar erectile dysfunction patterns can have widely different responses to the same alprostadil dose. The standard initiation pathway involves a low test dose (typically 1.25mcg to 5mcg) administered in a clinic setting, with observation of the response over the following hour. If the response is inadequate, a higher dose is tried at a subsequent visit. The aim is to find the lowest dose that produces a satisfactory erection lasting around 30 to 60 minutes, without producing a prolonged erection.
This titration process needs direct clinical observation because the consequences of an overdose include prolonged erection (priapism), which is a urological emergency. A man self-administering a first dose at home without supervision has no way to know in advance whether the dose will produce a normal-duration erection or a prolonged one.
Injection technique training matters
Intracavernosal injection technique is genuinely important. The injection site is on the lateral aspect of the proximal third of the penile shaft, avoiding the dorsal nerve and vein, the urethra on the ventral surface, and any visible surface veins. The needle is inserted at 90 degrees to the skin, the medicine is injected slowly over 5 to 10 seconds, and the site is compressed for several minutes after injection to reduce bruising and ensure adequate dispersion.
Done correctly, the technique is straightforward and the injection is well-tolerated. Done incorrectly, it can cause haematoma (significant bruising), pain, fibrosis of the corpus cavernosum, and over time the development of Peyronie’s-like plaques that can permanently affect erection quality and penile curvature. Repeated injections at the same site, injections too superficial or too deep, and inadequate post-injection compression all contribute to these complications.
In-person training by a clinical nurse or experienced prescriber, with the patient performing the first injection under observation, dramatically reduces these risks. Remote video instruction can supplement but cannot fully replace this hands-on initial training.
Priapism is a real and urgent risk
Priapism, defined as an erection lasting more than 4 hours, is a urological emergency. If not treated within around 4 to 6 hours of onset, the prolonged engorgement of the corpus cavernosum compromises blood flow to the cavernosal tissue and can cause permanent damage to the smooth muscle, leading to permanent erectile dysfunction. Untreated priapism beyond 24 hours typically causes irreversible cavernosal damage.
The risk of priapism with intracavernosal alprostadil is around 1 to 5% across studies, mostly in the early titration phase and at higher doses. Patients on Viridal Duo need a clear plan for what to do if priapism develops: ice packs, gentle physical activity (walking, climbing stairs), pseudoephedrine if available and not contraindicated, and most importantly, when and where to seek urgent urological care. The plan needs to be clear before the first injection, not figured out during the crisis.
This emergency planning is part of the initiation conversation that needs to happen in person, with the clinical team identifying which local A&E or urology service the patient should go to, what to say, and how to ensure prompt assessment.
Ongoing urological review
Men on long-term intracavernosal injection therapy benefit from periodic urological review for fibrosis, plaque formation, response changes, and the wider picture of their erectile function and general health. This is not always needed every visit, but the pathway should include access to urological assessment when relevant.
For all these reasons, Viridal Duo initiation is properly a clinical pathway involving direct medical supervision. Courier Pharmacy is well-placed to support the continuation phase of that pathway, but we are not the right place to start it.
Why choose Courier Pharmacy for Viridal Duo continuation supply
At Courier Pharmacy, our whole approach is built around the idea that healthcare should fit the person, not the marketing budget. For Viridal Duo specifically, that means honest framing about what we can and cannot offer: continuation supply for men already established on the medicine, with ongoing pharmacist support, careful interaction with your initiating clinical team, and clear signposting if your situation changes. Our service is shaped by the philosophy of Dr Ada Jex-Cori, our brand pharmacist, who has built her practice around accessible, honest, personalised care. Her view is straightforward: you are not broken. The system is the problem. We are here to change that.
What we offer
For men already initiated on Viridal Duo through an NHS urology clinic, private men’s health service, or other appropriate specialist pathway:
Reliable continuation supply at the maintenance dose established during your initiation
Discreet packaging and delivery
Ongoing pharmacist support for technique reminders, side effect questions, and practical advice
Coordination with your initiating prescriber where appropriate
Honest discussion if your situation has changed and you may need re-assessment
What we do not offer
First-time initiation of Viridal Duo through remote consultation. This needs to happen under direct clinical supervision in a clinic setting.
Continuation supply for men whose initiation history is unclear or who have not had appropriate clinical assessment.
Continuation supply where the dose or pattern of use suggests a need for re-titration or urological review.
If you are interested in starting Viridal Duo for the first time, we will be honest about the appropriate pathway. The standard route is referral from your GP to NHS urology, or a private men’s health clinic that offers intracavernosal injection initiation with in-person assessment and first-dose observation. We can talk you through this and signpost suitable services.
Men’s health that takes you seriously
For men dealing with erectile dysfunction, the NHS pathway can be variable in quality and access. Some men receive excellent care; others are dismissed, undertreated, or left without ongoing support. We see continuation supply of Viridal Duo as part of the wider work of supporting men’s health honestly and respectfully, without judgement and without the awkwardness that sometimes characterises this area of care.
For men with specific clinical situations (post-prostatectomy, spinal cord injury, severe diabetic ED, complex cardiovascular history), we recognise that intracavernosal injection therapy is often the right answer, and that maintaining a reliable supply with knowledgeable pharmacist support matters for quality of life. We will treat your situation with the seriousness it deserves.
Trust earned, not claimed
We are GPhC-regulated, we ground our content in NHS, NICE, BNF, MHRA, and European Association of Urology guidance, and we will tell you honestly if Viridal Duo continuation supply is not the right service for your situation. We would rather refer you on than supply where the clinical fit is not right.
How to order Viridal Duo (Prescription Only) from Courier Pharmacy
Viridal Duo is a Prescription Only Medicine. Supply through Courier Pharmacy is restricted to men who have already been initiated on the medicine through an appropriate clinical pathway and who are seeking ongoing continuation supply.
Here is how our service works:
Complete a quick online consultation answering questions about your erectile dysfunction history, your Viridal Duo initiation (when, where, by whom), your current maintenance dose, your ongoing clinical follow-up arrangements, and your current medicines and medical history.
A UK-qualified prescriber reviews your answers to confirm Viridal Duo continuation supply is appropriate for you. Where the prescriber needs additional information (a letter from your initiating clinic, evidence of ongoing follow-up, confirmation of dose), we will ask for it directly.
If approved, a prescription is issued and your order is prepared for dispatch.
We dispense and deliver discreetly to your door.
If Viridal Duo continuation supply isn’t the right service for you, we will explain why and suggest the next best option. That might be:
A referral to NHS urology through your GP if you need re-titration or specialist re-assessment.
A referral to a private men’s health clinic offering intracavernosal injection initiation if you are first-time treatment.
An oral PDE5 inhibitor (sildenafil, tadalafil) if oral medicine might be appropriate for your situation and you have not had a fair trial of these.
A different second-line option (intraurethral alprostadil MUSE, vacuum erection device) if injection therapy is not the right fit.
A discussion with your GP about wider cardiovascular and metabolic factors that may be contributing.
Our free fortnightly drop-in clinics at Insomnia, Derby run every other week from 12 to 1pm. Men’s health, erectile dysfunction, hair loss, mental health, cardiovascular and metabolic questions, and the broader conversations about ageing and wellbeing are all conversations we have regularly at these sessions. No appointment needed, no charge, no pressure.
What is the active ingredient in Viridial 10mcg injections?
Viridal 10 micrograms injection contains alprostadil as the active ingredient. Alprostadil is a man?made version of prostaglandin E1 (PGE1), a naturally occurring substance in the body. In erectile dysfunction treatment, it works by helping blood vessels in the penis relax and widen, which increases blood flow and supports an erection. Each dose delivers 10 micrograms (10 mcg) of alprostadil. Use it exactly as prescribed, and follow the training you’ve been given for safe injection technique and dosing.
What are Viridal 10 micrograms injection used for?
Viridal 10 micrograms injection is a prescription treatment for erectile dysfunction (ED) in adult men. ED means you find it difficult to get, or keep, an erection firm enough for sex. Viridal is used as a penile injection (an intracavernosal injection). Because it works locally, it can be a helpful option when ED tablets (such as sildenafil, tadalafil, vardenafil, or avanafil) haven’t worked well, aren’t suitable, or cause side effects you’d rather avoid.
Viridal contains alprostadil, which helps the blood vessels in the penis relax and widen. As a result, more blood can flow in and an erection can develop. It’s typically used when needed, shortly before sexual activity, rather than as a daily medicine. Your prescriber will usually start with a supervised “test dose” or a clear titration plan, because the goal is a reliable erection while avoiding an erection that lasts too long.
Viridal does not increase sexual desire, and it won’t work without sexual stimulation for everyone. However, many men like it because it can work even when stress, diabetes, nerve issues, or certain medicines make tablet treatments less effective.
Because it’s an injection, it’s important that you:
use the exact dose prescribed (do not guess or “top up”)
follow the training on where and how to inject
know when to get urgent help (for example, if you get a painful erection that lasts too long)
How do the Viridal 10 micrograms injections work
Viridal 10 micrograms contains alprostadil, a medicine that acts locally in the penis to help you get an erection. Alprostadil is a man?made version of prostaglandin E1 (PGE1), a substance your body naturally produces.
What it does in the body
When alprostadil is injected into the erectile tissue of the penis (the corpora cavernosa), it triggers a chain reaction that helps the smooth muscle relax and improves blood flow. In simple terms, it:
relaxes the muscle in the penile blood vessels, so they open wider
increases blood flow into the penis
helps trap blood inside the penis, which supports firmness
This effect happens because alprostadil binds to prostaglandin receptors and increases a messenger chemical inside cells called cAMP (cyclic adenosine monophosphate). Higher cAMP leads to smooth muscle relaxation, which is what allows the blood vessels to widen.
Why this is different from ED tablets
Many ED tablets (like sildenafil or tadalafil) rely on the nitric oxide pathway and sexual stimulation. Viridal works more directly at the site of action. That’s why it can still work for some men when tablets haven’t helped, including men with:
diabetes
nerve injury (including after prostate surgery)
reduced blood flow problems
certain medication?related ED
What you should expect
Most men who respond will notice an erection developing within a short time after injection. The aim is a firm erection suitable for sex, then a return to normal afterwards. Your prescriber will help find the lowest effective dose, because too much alprostadil can increase the risk of side effects.
Important safety note
Because Viridal can cause a prolonged erection, it’s important to follow your prescribed dose and the training you’ve been given. Seek urgent medical help if you develop an erection that lasts longer than you’ve been advised is safe, especially if it becomes painful.
How to use Viridal Duo
The information below is a summary for reference. The definitive guide is the patient information leaflet supplied with the product, supplemented by the training you received during initiation. If you are unsure about any aspect of technique or timing, contact our pharmacist or your initiating prescriber.
Preparing the device
Wash your hands thoroughly with soap and water.
Remove a single Viridal Duo dual-chamber syringe from the refrigerator and allow it to come to room temperature (around 10 to 15 minutes if it has been refrigerated, or skip this step if storing at room temperature).
Inspect the device for damage; do not use if the syringe is cracked, leaking, or shows visible damage.
Follow the device instructions to combine the powder chamber and the diluent chamber. The Viridal Duo system is designed to make this straightforward, with the activation mechanism integrated into the syringe body.
Gently rotate or shake the combined chambers as directed to dissolve the powder fully. The solution should be clear and colourless. Do not use if the solution appears cloudy, discoloured, or contains visible particles.
Attach the needle as directed (the needle is supplied with the device).
Expel any air bubbles by holding the syringe needle-up and gently tapping or expressing a small amount of solution.
Injecting
Choose an injection site on the lateral aspect of the proximal third of the penile shaft (the side of the upper third of the penis). Alternate sides between injections to avoid repeated trauma at the same site.
Avoid visible surface veins, the dorsal (top) midline (where the dorsal nerve and vein run), and the ventral (underneath) midline (where the urethra runs).
Clean the chosen injection site with an alcohol wipe and allow it to dry.
Hold the penis straight along its length with one hand, with the head of the penis between thumb and forefinger and the body of the penis stretched away from the body.
Insert the needle at 90 degrees to the skin surface, with a brisk, confident push to penetrate to the depth indicated in the device instructions (typically the full needle length is appropriate, depending on the device).
Slowly inject the contents of the syringe over 5 to 10 seconds.
Withdraw the needle in a single steady movement.
Apply firm pressure to the injection site with a clean tissue or cotton swab for at least 3 to 5 minutes to minimise bruising and ensure adequate medicine dispersion.
Dispose of the used needle and syringe in a sharps container.
After injection
The erection should begin within 5 to 20 minutes. Sexual activity can usually proceed as the erection develops. The erection should subside naturally within 30 to 60 minutes after injection, depending on dose.
If your erection lasts longer than 4 hours from the time of injection, this is priapism and a urological emergency. Follow your priapism action plan:
Apply ice packs to the perineum and penis.
Walk, climb stairs, or do light physical activity to redistribute blood flow.
Take pseudoephedrine 60mg if available and not contraindicated for you.
If the erection has not subsided within 4 hours of injection, go to your nearest A&E or urology service immediately. Tell them you have used intracavernosal alprostadil and have priapism; this is a recognised emergency and they will know what to do.
Do not try to manage prolonged priapism beyond 4 hours at home. The longer the priapism continues, the higher the risk of permanent damage to your erectile function.
Frequency
Do not use more than one Viridal Duo injection in any 24-hour period. Do not use more than three injections per week. Spacing injections appropriately reduces the cumulative risk of fibrosis and priapism.
Storage
Viridal Duo can be stored at room temperature (below 25°C) or refrigerated (2 to 8°C), depending on the specific product packaging. Check the patient information leaflet for the specific storage requirements of the version supplied. Do not freeze. Protect from light. Keep out of sight and reach of children.
The shelf life is indicated on the packaging. Do not use after the expiry date.
Warnings and precautions for Viridal Duo
Priapism
The most clinically important warning. An erection lasting more than 4 hours is a urological emergency. Follow your priapism action plan and seek urgent urology care if the erection does not subside within 4 hours of injection. Untreated priapism can cause permanent erectile dysfunction.
Patients who have had priapism before, who have a higher dose requirement (suggesting higher cavernosal sensitivity to alprostadil), or who have certain blood disorders (sickle cell disease, leukaemia, multiple myeloma) face higher priapism risk and need particularly careful dose management.
Bleeding and bruising at injection site
Minor bleeding and small bruises at the injection site are common, particularly in the first few weeks. Significant haematoma is uncommon but can occur if the technique is poor or if a vein is punctured. Adequate post-injection compression (3 to 5 minutes of firm pressure) reduces this risk.
Patients on anticoagulants (warfarin, DOACs like apixaban, rivaroxaban, edoxaban, dabigatran) have a higher bleeding risk. Discuss with your prescriber whether intracavernosal injection therapy is appropriate for you, and consider longer post-injection compression times.
Fibrosis and Peyronie's-like changes
Long-term intracavernosal injection therapy can cause development of fibrotic nodules or plaques in the corpus cavernosum, particularly when injection technique is suboptimal or when the same site is used repeatedly. These changes can affect erection quality and cause penile curvature similar to Peyronie's disease.
Strategies to reduce risk: alternate injection sites with each injection (left and right sides), use the correct injection technique, do not exceed the recommended frequency, and have periodic urological review to assess for early fibrotic changes.
Cardiovascular considerations
Intracavernosal alprostadil has minimal systemic effects at standard doses, but men with significant cardiovascular disease should still be assessed for fitness for sexual activity itself before being initiated on injection therapy. Sexual activity is exercise; men whose cardiovascular condition makes them unfit for moderate exercise need cardiology review before pursuing pharmacological erectile dysfunction treatment.
Sickle cell disease and blood disorders
Men with sickle cell disease, multiple myeloma, leukaemia, or thrombocythaemia face higher priapism risk and need particularly careful assessment before intracavernosal injection therapy. Alprostadil is generally not the first-choice approach in these conditions.
Anatomical considerations
Men with significant penile deformity, anatomical abnormalities (such as severe Peyronie's disease, penile implant, severe phimosis), or conditions predisposing to priapism may not be suitable for intracavernosal injection therapy. The initiating clinician will have assessed this.
Bleeding disorders and anticoagulation
Men with bleeding disorders or on anticoagulant medicines face higher bleeding risk at the injection site. Discuss with your prescriber.
HIV transmission
The needle used for intracavernosal injection is a sharp object that should be disposed of safely. If the device or needle is shared (which it should never be), there is a theoretical risk of HIV, hepatitis B, and hepatitis C transmission. Always use a fresh syringe and needle for each injection. Never share devices.
Partner safety
Alprostadil is essentially not systemically absorbed and does not cross into ejaculate in pharmacologically active amounts. However, partners of men using intracavernosal alprostadil who are pregnant or trying to become pregnant should discuss any concerns with the prescriber. The data on partner exposure during sexual activity is limited but reassuring.
Driving and machinery
Intracavernosal alprostadil does not impair driving or machinery operation directly. After injection, the medicine should not affect alertness or coordination.
Side effects of Viridal Duo
Common side effects (affecting up to 1 in 10 patients)
Penile pain or discomfort, particularly in the first few uses
Minor bleeding or bruising at the injection site
Prolonged erection (1 to 4 hours; priapism is the more serious category beyond 4 hours)
Penile fibrosis (over time with long-term use)
Penile angulation or curvature (related to fibrosis or injection technique)
Less common side effects
Significant haematoma at injection site
Penile rash or skin reaction
Local infection (rare with appropriate hygiene)
Hypotension (uncommon with intracavernosal use; more relevant with higher doses or alternative routes)
Dizziness (uncommon)
Headache (uncommon, unlike oral PDE5 inhibitors)
Rare but serious side effects
Priapism lasting more than 4 hours (urological emergency)
Significant cavernosal fibrosis or Peyronie's-like plaque formation
Severe allergic reactions (anaphylaxis is very rare with alprostadil)
Penile gangrene (very rare, associated with severe untreated priapism)
Stop and seek urgent help if
Your erection lasts longer than 4 hours from injection (priapism: go to A&E or urology service immediately)
You develop severe penile pain that does not settle
You develop signs of infection at the injection site (significant redness, warmth, swelling, fever)
You develop a severe allergic reaction (swelling of face/lips/tongue, difficulty breathing)
You notice new penile curvature, lumps, or plaques developing
Yellow Card reporting
Suspected adverse drug reactions can be reported to the MHRA via the Yellow Card scheme at yellowcard.mhra.gov.uk. Reporting helps build the safety picture for everyone.
Drug interactions with Viridal Duo
Intracavernosal alprostadil has minimal systemic absorption, so drug interactions are largely not pharmacologically significant. The interactions to consider are mostly about combining alprostadil with other medicines that affect erectile function or that affect bleeding.
Significant considerations
Anticoagulants (warfarin, DOACs): increase the risk of bleeding and haematoma at the injection site. Use longer post-injection compression and discuss with your prescriber.
Antiplatelet medicines (aspirin, clopidogrel): minor increase in bleeding risk at the injection site.
Other erectile dysfunction medicines: do not combine intracavernosal alprostadil with oral PDE5 inhibitors (sildenafil, tadalafil, vardenafil, avanafil), other intracavernosal injections (papaverine, phentolamine), or intraurethral alprostadil (MUSE) without specific prescriber guidance. The combination can cause prolonged erection and priapism.
Recreational substances: cocaine, amphetamines, and other vasoactive recreational drugs can interact unpredictably with alprostadil and increase priapism risk. Discuss honestly with your prescriber.
Not significant interactions
Because alprostadil is not significantly systemically absorbed, most commonly co-prescribed medicines do not interact with it in a clinically meaningful way. Antihypertensives, statins, antidepressants, acid-suppression medicines, antihistamines, and most other systemic medicines can be taken normally.
Importantly, nitrate medicines (GTN, isosorbide mononitrate, isosorbide dinitrate) do not have the same dangerous interaction with intracavernosal alprostadil as they do with oral PDE5 inhibitors. This is one of the reasons alprostadil injection therapy is sometimes appropriate for men with cardiovascular disease who cannot take oral PDE5 inhibitors.
Frequently asked questions about Viridal Duo
What is Viridal Duo?
Viridal Duo is a UK Prescription Only Medicine containing alprostadil, a synthetic version of prostaglandin E1. It is delivered through a dual-chamber injection system designed for self-injection directly into the corpus cavernosum of the penis. It is used for erectile dysfunction in men where oral PDE5 inhibitors (sildenafil, tadalafil, vardenafil, avanafil) have not been effective, contraindicated, or not the right fit.
How does Viridal Duo work?
Alprostadil acts directly on the smooth muscle of the corpus cavernosum, causing relaxation, dilation of the small arteries, and reduced venous outflow. The combined effect is engorgement of the erectile tissue and erection. The mechanism is independent of the nitric oxide pathway that drives normal physiological erection, which is why it works in men where oral PDE5 inhibitors do not.
How quickly does it work?
The erection begins within 5 to 20 minutes of injection and lasts approximately 30 to 60 minutes depending on dose and individual response.
Does the erection need sexual stimulation?
No. The erection produced by intracavernosal alprostadil does not depend on sexual stimulation, although stimulation may enhance the response in some men. This is different from oral PDE5 inhibitors, which require sexual stimulation to produce an erection.
Why won't Courier Pharmacy initiate me on Viridal Duo?
Because first-dose titration needs direct clinical supervision in a clinic setting. The right dose cannot be predicted from clinical history alone, and the risk of prolonged erection (priapism) makes unsupervised first dosing unsafe. Injection technique training is also better done in person with hands-on supervision. We supply Viridal Duo as a continuation service for men already established on the medicine.
How do I get started if I have not used Viridal Duo before?
The standard route is referral from your GP to NHS urology services, or self-referral to a private men's health clinic that offers intracavernosal injection initiation. The initiating service will assess your suitability, perform first-dose titration under observation, and provide injection technique training. Once you are established on a maintenance dose with confirmed safe technique, you can come to us for continuation supply.
What strengths are available?
Viridal Duo is typically available in 10mcg, 20mcg, and 40mcg strengths in UK practice. Most men settle on a maintenance dose between 5mcg and 40mcg per injection, established during clinical titration.
How often can I use Viridal Duo?
Not more than one injection per 24 hours, and not more than three injections per week. Spacing injections appropriately reduces the risk of fibrosis and priapism.
What is priapism and what should I do if it happens?
Priapism is an erection lasting more than 4 hours and is a urological emergency. If your erection has not subsided within 4 hours of injection, apply ice packs, do light physical activity, take pseudoephedrine 60mg if available and not contraindicated, and most importantly go to your nearest A&E or urology service immediately. Tell them you have used intracavernosal alprostadil. Untreated priapism beyond 4 to 6 hours can cause permanent damage to your erectile function.
Is Viridal Duo painful?
There is often some discomfort during and immediately after the first few injections. With practice and correct technique, most men find the procedure becomes very manageable. The discomfort is usually mild and brief. Significant or persistent pain warrants discussion with the prescriber, because it may indicate technique issues or early fibrosis.
Where do I inject?
On the lateral aspect (side) of the proximal third (upper third) of the penile shaft. Alternate sides between injections to avoid repeated trauma at one site. Avoid visible surface veins, the dorsal midline (where the dorsal nerve runs), and the ventral midline (where the urethra runs).
Will my partner be affected?
Alprostadil is essentially not systemically absorbed at intracavernosal doses and does not cross into ejaculate in pharmacologically active amounts. Partners are not significantly exposed. Partners of men using intracavernosal alprostadil who are pregnant or trying to become pregnant should discuss any concerns with the prescriber for reassurance.
Can I drink alcohol on Viridal Duo?
Moderate alcohol is not specifically contraindicated, but heavy alcohol intake reduces erectile function regardless of medicine use. Sensible drinking is sensible.
Can I use Viridal Duo with nitrate medicines?
Yes. Unlike oral PDE5 inhibitors, intracavernosal alprostadil does not have the dangerous interaction with nitrates that sildenafil, tadalafil, vardenafil, and avanafil have. This is one of the main reasons men taking nitrates are offered intracavernosal injection therapy.
Can I use Viridal Duo if I have heart disease?
Often yes, but the assessment is about your fitness for sexual activity itself rather than the medicine specifically. Sexual activity is exercise; men whose cardiovascular condition is not stable enough for moderate exercise need cardiology review before pursuing pharmacological erectile dysfunction treatment. The lack of systemic effects of intracavernosal alprostadil is an advantage compared to oral PDE5 inhibitors in some men with cardiovascular disease.
Can I use Viridal Duo if I am on anticoagulants?
Often yes, but with extra care about injection technique and longer post-injection compression to minimise bleeding and haematoma. Discuss with your prescriber.
What if Viridal Duo is not producing an erection anymore?
Loss of response over time can happen and warrants urological review rather than self-managed dose escalation. The review will consider whether the dose needs adjustment, whether fibrosis or other anatomical changes have developed, whether your cardiovascular or metabolic situation has changed, and whether alternative or additional treatments would be appropriate.
Are there alternatives to Viridal Duo?
Yes, several. Oral PDE5 inhibitors (sildenafil, tadalafil, vardenafil, avanafil) remain first-line for most men. Intraurethral alprostadil (MUSE) is an alternative non-injection route. Combination intracavernosal injections (alprostadil with papaverine and/or phentolamine, "trimix" or "bimix" preparations) are used in some specialist settings. Vacuum erection devices are a non-pharmacological option. Penile prosthesis surgery is the third-line option for men where medical management has not been sufficient.
How should I store Viridal Duo?
Check the patient information leaflet for the specific storage requirements of the version supplied. Viridal Duo can typically be stored at room temperature (below 25°C) or refrigerated (2 to 8°C). Do not freeze. Protect from light. Keep out of sight and reach of children. Do not use after the expiry date.
How do I dispose of used syringes?
Used syringes and needles should be disposed of in a sharps container. If you do not have one, contact our pharmacist or your GP for advice on obtaining one. Do not put used needles in domestic waste.
How do I order Viridal Duo continuation supply from Courier Pharmacy?
Complete the online consultation at courierpharmacy.co.uk. The consultation covers your initiation history, maintenance dose, current clinical follow-up, and medical history. A UK-qualified prescriber will review your answers and confirm whether continuation supply is appropriate. We may ask for evidence of your initiation (a letter from your initiating clinic, for example). If approved, the order is dispatched discreetly to your door.
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 10 am to 12 pm. Bring a question, bring a friend, bring a stack of bewildering letters from another clinic; we'll sit with you. We cover men's health, erectile dysfunction, hair loss, weight management, mental health, MCAS, fibromyalgia, low-dose naltrexone, and whatever else people bring through the door. No appointment. No cost. No pressure. Learn more about our community talks.
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. Grounded in the latest NHS, NICE, BNF, EMC, MHRA, European Association of Urology, and British Association of Urological Surgeons guidance, peer-reviewed studies, and the real questions patients bring to our drop-in clinics in Derby.
