Caverject Injections for Erectile Dysfunction: A UK Patient Guide

Caverject is a prescription injection containing alprostadil (prostaglandin E1) that produces an erection directly, without needing sexual arousal to trigger the process. It is injected into the side of the penis and works within 5 to 20 minutes. For men whose ED has not responded to tablets like sildenafil or tadalafil, it remains one of the most effective options available.

How Caverject Works#

Alprostadil relaxes the smooth muscle inside the corpora cavernosa (the two chambers that run along the length of the penis) and widens the local blood vessels. Blood fills those chambers and stays there, producing a firm erection. Because the drug acts locally rather than through general circulation, it bypasses the nitric oxide pathway that PDE5 inhibitors depend on. This is why it works for men with vascular disease, nerve damage after prostatectomy, or diabetes-related ED, even when tablets have failed.

The erection produced by Caverject is not dependent on arousal, which is useful medically but worth knowing before your first injection.

Who Is It For?#

Caverject is licensed in the UK for erectile dysfunction as a second-line treatment. It is particularly well-suited to:

• Men who have not responded to sildenafil or tadalafil at maximum doses
• Post-prostatectomy ED, where nerve-sparing surgery was not possible or has left residual dysfunction
• Diabetes-related ED, where vascular and neuropathic changes reduce the effectiveness of oral treatments
• Men who cannot take PDE5 inhibitors because of nitrate use for heart disease

Research has found that intracavernosal alprostadil can produce satisfactory erections in a significant proportion of men with diabetes-related ED, a group who typically respond poorly to tablets.

NHS Access and Private Prescribing#

This is where UK patients are often poorly informed. Caverject can be prescribed on the NHS, but access depends on your underlying condition.

NICE Technology Appraisal TA11 restricts NHS funding of PDE5 inhibitors to men with specific conditions (diabetes, prostate cancer treatment, kidney dialysis, severe pelvic injury, and others). Alprostadil is governed by different rules and NHS access is determined by local formulary decisions and clinical pathway, typically via urology. Men with post-prostatectomy ED in particular are often eligible for NHS alprostadil prescriptions via urology. Your GP can refer you to a urologist or NHS sexual health clinic, where your first injections will be supervised and your technique assessed before you self-inject at home.

Privately, Caverject is available on prescription from a GP, urologist, or online prescribing service registered with the CQC. It is not a controlled drug. The cost varies, but expect to pay roughly £15 to £30 per vial privately depending on dose and pharmacy. It is not available over the counter.

Dose Titration#

Dosing is individual. Your prescriber will start low and adjust based on your response. The table below gives a typical starting framework:

The maximum doses shown represent the licensed upper limits, not routine treatment targets. Most men are managed on considerably lower doses, and any increase must be directed by your prescriber. Your first injection should always be given under clinical supervision. Do not attempt dose titration alone. The goal is an erection lasting 30 to 60 minutes that resolves on its own.

You should not inject more than once in 24 hours, and the recommended maximum is three injections per week. Exceeding this raises your risk of penile fibrosis (scar tissue), which over time can cause curvature similar to Peyronie's disease.

How to Inject Safely at Home#

Once trained by a clinician, the process follows these steps:

1. Reconstitute the powder with the supplied diluent if using standard Caverject vials (Caverject Dual Chamber comes pre-mixed).
2. Draw up the prescribed dose using the needle recommended by your clinician during your training session.
3. Sit or stand. Stretch the penis gently to the side with your non-dominant hand.
4. Inject at the 3 o'clock or 9 o'clock position (the side, never the top, bottom, or tip) into the corpus cavernosum.
5. Apply gentle pressure to the injection site for 1 to 2 minutes after withdrawing the needle.
6. Dispose of used needles in a sharps bin. UK local councils provide free sharps bins, and many pharmacies will accept used containers under take-back schemes. Do not put needles in household bins.

Reconstituted Caverject should be stored in a refrigerator and used within 24 hours. Storage requirements for unreconstituted vials vary by formulation — Caverject Dual Chamber must be refrigerated, while other presentations have different requirements. Always follow the specific instructions in your pack, as conditions and shelf life differ.

Priapism: The One Serious Risk#

Priapism is a prolonged erection not caused by arousal. With Caverject, the risk is low when doses are correctly titrated, but it is a medical emergency if it occurs.

If your erection lasts more than 4 hours, go to A&E immediately. Tell the triage team you have had an intracavernosal alprostadil injection. Treatment typically involves an injection of a vasoconstrictive drug (phenylephrine) directly into the penis to reverse the blood flow. If left untreated beyond 6 hours, permanent damage to erectile tissue can occur.

Do not wait and see. Four hours is the threshold, not a rough guide.

Other Side Effects#

Most side effects are mild and local:

• Pain or aching at the injection site (the most common complaint, affecting around 1 in 3 men)
• Mild bruising
• Small haematoma (blood pooling under the skin)
• Prolonged erection (managed by correct dosing)

With repeated long-term use, a small proportion of men develop penile fibrosis, felt as a firm nodule along the shaft. Report any new lumps or curvature to your prescriber. Regular injection site rotation reduces this risk.

Caverject is not suitable for men with sickle cell disease, penile anatomical abnormalities, or hypersensitivity to alprostadil. Men taking anticoagulants such as warfarin or direct oral anticoagulants (DOACs) require careful assessment before starting injection therapy, as there is an increased risk of bruising or haematoma at the injection site; this does not automatically exclude use but must be discussed with your prescriber, who can advise on appropriate technique and precautions.

Caverject vs Other Options#

MUSE is a urethral pellet containing the same drug. It avoids needles but is generally less effective than injection. Trimix is a compounded mixture of alprostadil, phentolamine, and papaverine; it is not a licensed UK product and is private-only, but some men tolerate it better with less injection site pain.

For men whose ED does respond to oral treatment, options like sildenafil and tadalafil remain simpler to use. You can see the full range of oral ED treatments available in the UK at Totiva's ED service page.

Injection Anxiety and Spontaneity#

Many men worry that self-injection will feel clinical or disrupt intimacy. This is a real concern and worth discussing with your prescriber rather than abandoning the treatment before trying it. Most men find that after their first few successful injections at home, the process becomes routine. Some couples involve the partner in preparation, which can reduce the sense of interruption. The injection takes about two minutes and acts within 5 to 20 minutes, which is similar to the planning window needed for a PDE5 inhibitor on an empty stomach.

If injection anxiety is significant, speaking to a psychosexual therapist alongside physical treatment often helps. Your GP or urologist can refer you.

For a broader look at ED treatments available in the UK, including how oral and injectable options compare, the British Society for Sexual Medicine publishes guidelines that your clinician will follow when recommending a treatment pathway.