Proscar (finasteride) is making a return visit as our Drug of the Month, following some sensational revelations. Manufactured by Merck, it has quickly established itself as the treatment of choice for benign enlarged prostate in the US and the UK.

But this has suddenly been thrown into question by a new study conducted by the University of Washington which shows that finasteride is no more effective than a sugar pill. Researchers tracked 1,229 patients, aged between 45 and 80, for a year to see if the drug was effective compared to terazosin, an alpha blocker, and a placebo. They found no difference between the finasteride and placebo groups, using quality of life measures.

The finding is contrary to an earlier trial which showed that the drug was very effective in reducing the prostate over a year. But the original trial apparently involved men with larger prostates, whereas those in the University of Washington survey had prostates of a size found more generally "in the real world," as research team leader Professor Michael Brawer put it to a conference recently.

All of this may be bad news for earlier finasteride patients who suffered from one of the side effects that come with the drug. These include impotence, reduced sexual interest, breast tenderness and enlargement, and hypersensitive reactions, such as lip swelling and skin rash.

These reactions have been observed among patients taking the standard, recommended dose of 5 mg a day. In tests on mice, death has occurred with single dosages of 1500 mg.

One piece of good news for prostate sufferers: the Washington study did find that terazosin was very effective in treating patients with prostates that had enlarged to a more usual size. Improvements were noted within two weeks.