Tablets and PDE-5 inhibitors such as Spedra, Viagra, Levitra and Cialis aren’t suitable for everyone experiencing ED. Some men may have serious side effects, such as blisters or serious skin reactions, or an allergic response to the treatment.

Having had difficulties with tablets, you may find that injections are a suitable alternative. Their effects can generally be felt more quickly than oral medication; because the product is injected directly into the penis itself, it becomes active in the body very rapidly (within five to 15 minutes). 

An injection into the penis may sound unnerving, but having been shown how to administer it by a doctor or nurse, men typically grow accustomed to the process after the first few uses. 

Injections for ED contain a drug called alprostadil, which is the same chemical that the penis produces when it becomes erect naturally. Alprostadil enables the muscles and blood vessels in the penis to relax, and this facilitates greater blood flow to it, making it easier to get and sustain an erection. 

There are currently two alprostadil-based injectable products on the market: Viridal and Caverject. They are available in a range of dosages, but you should consult your doctor prior to purchase for guidance on how to use them. Your doctor will also determine what dosage you start on.


Viridal 10mcgOnce you have established what the most suitable dose is for you, Viridal should enable you to achieve an erection between five and 15 minutes. It usually works for up to one hour. 

In utilising the chemical alprostadil, Viridal provides men with a replacement synthetic for another chemical, prostaglandin E1 (PGE1). PGE1 instructs blood vessels near the penis to allow blood in. If this chemical isn’t working as it should, it makes it difficult for men to get an erection. This is where alprostadil comes in.


caverjectThere are two types of Caverject available to buy: Caverject Vials and Caverject Dual Chamber. While their functionality is the same, they’re calibrated for use slightly differently. The vial contains a powder and a solution, which need to be mixed together before the vial can be utilised and injected into the base of the penis. The Caverject dual chamber however just requires the plunger to be turned to mix the solution.  

Both products are manufactured by Pfizer and consist of alprostadil in freeze-dried, or ‘lyophilised form’. This gives the drug greater protection from heat, light and other risk factors in the external environment. 

You (or your partner) will be shown by a doctor or nurse how to inject the drugs into the shaft of the penis when you want to achieve an erection (up to three times per week and no more than once daily). 


Invicorp 25mcgIn the event that you find injections of alprostadil ineffective or uncomfortable, Invicorp may be the solution. It’s made up of two different active ingredients, aviptadil and phentolamine mesilate, which work in tandem to enhance blood flow to the penis and reduce blood flow away from the penis. 

Phentolamine mesilate reduces arterial blood pressure, making blood flow into the penis easier. Aviptadil functions similarly, but allows blood to remain in the penis once it’s stimulated, producing improved and more extensive erections. 

How long can I sustain an erection for with ED injections? 

Erections via injections can typically be sustained for an hour. They may, in rare circumstances, persist for longer if an excessive dosage has been administered.  

Although injections can usually take effect more rapidly than ED tablets, their half-life is comparatively considerably shorter. Oral medication can remain active in the body for as long as five hours at a time - five times the length of injections, on average. Nevertheless, this shorter window should be sufficient from an intercourse perspective for the majority of men. 

Side Effects 

Like tablets, injections may produce side effects, ranging from pain (infrequent), to a burning sensation or a small swelling in the penis shaft (this will disappear provided you rotate the site of injection, which you should do regularly). Priapisms (when an erection endures for four hours) are also a potentiality, and require medical attention immediately. 

What if neither ED tablets or injections are suitable for me?

If you discover that neither ED tablets or injections are suitable for you, you may want to try a cream. Vitaros cream works slightly differently to oral medication and alprostadil-based treatments. You can find out more about Vitaros and other creams for ED here

It may also be worth discussing pumps, implants or surgery, or lifestyle fixes and counselling, as potential solutions with your doctor. 

Page last reviewed:  29/09/2021