Erectile dysfunction injections — how they work and what to expect
Quick answer
Erectile dysfunction injections, usually alprostadil, are placed into the side of the penis to widen blood vessels and produce an erection within minutes. They are generally considered when tablets have not worked well or are not suitable, and are prescribed only after a clinical assessment covering technique, dosing limits and safety.
What are erectile dysfunction injections?
Erectile dysfunction (ED) injections are a prescription-only treatment given directly into the penis to help produce an erection. In the UK, the medicine used is almost always alprostadil, a substance closely related to one the body already makes, which relaxes and widens blood vessels so more blood can flow in.
They are sometimes described as "self-injection therapy" because, after training from a clinician, most men learn to give the injection themselves at home before sexual activity. This route bypasses the digestive system entirely, which is one reason it can work for men who do not respond well to tablets, and why it is often grouped with other "second-line" treatments alongside a vacuum pump.
The name can sound daunting, and it is common to feel apprehensive before trying it for the first time. In practice, a clinician talks through every step in advance, and the equipment used is designed to make self-injection as straightforward and low-anxiety as possible.
How do ED injections work?
A fine needle is used to deliver a small, individually calculated dose of alprostadil into the side of the penis. Because the medicine acts locally, at the site where it is needed, it does not rely on the same absorption process as a tablet taken by mouth, and it is not affected by food or by how the digestive system is working that day.
Many men notice an erection begins within around five to twenty minutes, and unlike tablets, which support an erection during arousal, an ED injection can produce an erection with or without sexual stimulation. This is one of the key differences clinicians discuss during an assessment, since it changes how and when the treatment is used, and means it can suit men whose ED has more to do with reduced blood flow than with arousal itself.
Who might be offered ED injections?
Injections are usually considered a second-line option, meaning they tend to be discussed after tablets such as PDE5 inhibitors have not worked well enough or cannot be taken, for example because of an interaction with other medicines such as certain nitrates. They may also suit men whose ED has a strong physical or vascular component, such as after prostate surgery or with long-standing diabetes, where tablets alone have limited effect.
They are not right for everyone. A clinician will ask about your medical history, current medicines, and any conditions affecting blood clotting or the structure of the penis, such as Peyronie's disease, before deciding whether injections are suitable. They will also explain the alternatives, including a vacuum pump or an alprostadil cream such as Vitaros (Alprostadil Cream), which is applied rather than injected, so you can weigh up which approach fits your circumstances and preferences.
How are the injections given?
If injections are agreed as suitable, the first dose is usually given and observed in a clinical setting so technique and response can be checked safely, and so any questions about the process can be answered in person. After that, most men are taught to inject themselves at home, typically into the side of the penis at the base, avoiding visible veins, using a fine needle designed to make the process as comfortable as possible.
Dosing is individual and is built up gradually to find the amount that produces a comfortable, functional erection without lasting too long, since too high a dose raises the risk of a prolonged erection. To reduce the risk of scarring or nodules developing inside the penis, injections are not used more than once in any 24-hour period, and there is a limit on how many times they can be used each week. Your clinician will give you a specific dosing schedule to follow, along with guidance on rotating the injection site.
Side effects and safety
The most common side effects are mild discomfort or aching at the injection site, and occasionally minor bruising, both of which usually settle quickly. Some men notice a change in the angle or firmness of an erection over time with repeated use, or small areas of firmness under the skin, which is worth mentioning at a review so your clinician can adjust the approach if needed.
The most important safety issue is priapism, an erection that does not go down on its own after sexual activity has finished. An erection lasting longer than around two hours should be treated as urgent and discussed with a pharmacist, GP or NHS 111 promptly; one lasting four hours or more is a medical emergency and needs immediate attention at A&E, because prolonged priapism can cause lasting damage to the tissue of the penis if it is not treated quickly. This is explained clearly as part of any assessment for injection therapy, along with exactly what to do and who to contact if it happens, so you feel prepared rather than caught out.
How do injections compare with tablets and other options?
Tablets remain the usual starting point for most men because they are straightforward to take and do not involve a needle. Injections are generally reserved for when tablets are not effective enough, are not tolerated because of side effects, or are ruled out by another health condition or medicine, such as certain heart medicines.
Some men are understandably put off by the idea of self-injecting, and this reaction is common and plays a real part in the decision. A vacuum pump is a non-drug alternative that some prefer, working mechanically to draw blood into the penis rather than using medicine, while Vitaros (Alprostadil Cream) offers a non-injected way of using the same type of medicine, applied to the tip of the penis rather than injected into the shaft. There is no single "best" option among these; the right choice depends on how quickly you need it to work, how long you want the effect to last, your other health conditions, and personal preference, all of which a clinician can talk through with you at your own pace.
Practical considerations and talking to a partner
Alprostadil injections need to be stored correctly, usually in a fridge, and any unused doses should be disposed of following the instructions given with the prescription. Needles and sharps should always be disposed of in an approved sharps container rather than in household waste, and your pharmacy can advise on arranging safe collection.
Many men also find it helpful to involve a partner in the conversation, both to explain what to expect and to reduce any awkwardness around timing, since the injection is usually given a short while before sexual activity. There is nothing unusual about needing a period of adjustment; most men become more confident with the technique after the first few attempts, and follow-up appointments are a normal part of getting the dose and routine right.
What to expect from a consultation
A consultation for ED injections typically covers your medical history, current medicines, and any previous ED treatments you have tried, along with a discussion of what has and has not worked and why. Your clinician will explain how alprostadil injections are given, the dosing limits, storage and disposal, and the warning signs of priapism to watch for, so you leave with a clear, practical understanding of the treatment.
If injections are agreed as an appropriate option, you will usually be shown the technique and given a starting dose to try under supervision, with a follow-up to review how it is working and adjust the dose if needed. Ongoing prescribing is subject to clinical suitability at each review, and you can raise any concerns, including whether a different treatment might suit you better, at any point.
Frequently asked questions
Do ED injections hurt?
Most men describe a brief pinprick or mild sting rather than significant pain, since a very fine needle is used. Any discomfort usually settles quickly, and a clinician can advise on technique to help minimise it.
How quickly do ED injections work and how long do they last?
An erection typically begins within around five to twenty minutes of the injection. How long it lasts varies with the dose and the individual, which is why doses are adjusted gradually under clinical guidance.
Can I use ED injections if tablets have not worked for me?
Injections are often considered specifically for this situation, as they work locally rather than relying on the digestive system. A clinician can assess whether they are a suitable next step for you.
Is Trimix available in the UK?
Compounded mixtures such as Trimix are not routinely prescribed in the UK. The standard prescription option is alprostadil, given as an injection or as a cream such as Vitaros.
What should I do if the erection does not go down?
An erection lasting more than around two hours should be discussed promptly with a pharmacist, GP or NHS 111. One lasting four hours or more is a medical emergency and needs immediate attention at A&E.
Are ED injections available on the NHS?
Access varies by local NHS trust and individual circumstances. A clinician can discuss the options available to you, including private prescription where appropriate, subject to suitability.