Erectile dysfunction alprostadil
Erectile dysfunction gained huge public awareness with the introduction of Pfizer's sildenafil (Viagra), and a condition that was once taboo became a huge topic of conversation. It rapidly became a big potential moneyspinner for the pharmaceutical companies, with the number of sufferers estimated at more than 70 million around the world.1
The big advantage of sildenafil is that, as an oral formulation, it is simple to take. On the down side, its origins as a heart drug mean that it cannot be taken by men with certain cardiac conditions, notably those who have to take organic nitrate heart drugs like glyceryl trinitrate.
Alprostadil, which is being developed by MacroChem under the brand name Topiglan, can be taken by such patients. The active is already on the market for the treatment of erectile dysfunction, being sold by Pharmacia as Caverject, which must be administered by intracavernosal injection. Although not a tablet formulation, Topiglan is a topical gel, which is still an infinitely preferable route of administration to the alternative of unpleasant local injections.
The compound is a synthetic version of prostaglandin E1, a hormone found naturally in human semen. The gel is applied to the glans of the penis prior to intercourse. It contains 1% of the active, and 5% of MacroChem's SEPA (soft enhancer of percutaneous absorption), a patented excipient that promotes drug absorption.
Initial Phase III trials have shown its effectiveness in use.2 Early results show that more patients using the gel achieved acceptable rigidity than those in the control group. Responses to alprostadil were greater than to the placebo at all time points after the gel was applied, and the greatest differences were seen at 45 and 60min.
However, the target for maintaining erection was not hit, which may be a result of an unexpected decrease in potency seen in returned, unused samples. This was attributed to an interaction with components of the unit dose dispenser being used. The company has since developed a blister-type dispenser, which it plans to use in future trials, and it hopes this will solve the problem of potency reducing on storage.