Health and Prostate

Question: What are the short and long-term side effects of finasteride (Proscar)?

Answer: The main side effect is impotence, but only in about 6% compared to 3% on placebo. That is to be expected with men of that age who are followed for a long time. Some men will for one cause or another will report impotence – that’s just the natural history of aging. No other significant side effects have been reported, either biochemical or subjectively perceived. This has been very thoroughly studied under the Good Clinical Practice international rules – any disorder that any subject has during the study period is registered, even if it’s unrelated to the drug. In our trial, 40% of the men already reported sexual dysfunction at the start of the trial, and we estimated that we might have had over-reporting of impotence because it was listed in the patient information as a possible side effect. When you alert the patients to anticipate a side effect, it is more frequently reported because they’re watching for it and they’re going to attribute it to the medication. We have data now for six years of treatment, which hasn’t altered the picture – the side effects have not increased or changed. The patients who have had a good response find that efficacy is maintained over that time – tolerance has not developed.

Question: How many benign prostatic hyperplasia (BPH) sufferers could benefit from finasteride (Proscar)? Which factors determine who should receive it?

Answer: This comes down to the question of who is a good responder, and what is a good response. Is it complete abolition of symptoms or just a 50% improvement, enough to make the patient feel just like a normal elderly man? The degree of prostate gland enlargement is the key factor that predicts outcome of treatment. We performed a meta-analysis, pooling the results from similar trials, so we now have data from over 4,000 patients. This analysis clearly showed that men with more enlarged prostates, over 40 g, have a more significant benefit from the drug. The mean size of the prostates in our study was about 41 g, meaning half the men had prostates larger than that, and half smaller. In our estimation, about 40% of patients have the best effect from the drug, significantly better than reported in the trial. About 20% dropped out over the two years of the study, and the main reason was lack of expected efficacy. If you use the principle “intention to treat”, which means including results from every patient initially enrolled in a study, you get a true picture of what happens to the whole population you treat. It actually diminishes the end results, but it’s regarded as state of the art statistics. The intention is to see in a large group of patients what happens to the whole group, whether they stay in the trial or drop out.