Alprostadil

This drug is safe for most men to use (it can be used by the majority of men who cannot be safely prescribed Viagra) and it can either be injected directly into the penis or inserted in the form of a small pellet into the urethra.

When injected, seven out of ten men achieve an erection sufficient for sexual intercourse that lasts for at least 30 minutes.

The main problem with injections is that they can be painful and some men develop nodules in the shaft of their penis. If the dose is too high, a prolonged erection (a condition known as priapism) can also occur. The side-effects cause significant numbers of men to stop using this method of treatment.

The pellets are slightly less effective than injections, working for about two-thirds of men. The most common side-effect is penile pain, and partners may also experience some burning if the drug leaks out during intercourse.