In what might be the most sterling example of the cure being worse than the disease, a recently published study in Hormone Molecular Biology and Clinical Investigation has found that a popular drug used to treat benign prostate enlargement may worsen its users’ sexual dysfunction and lower their testosterone levels to the point of nonexistence.

Spearheaded by Dr. Abdulmaged M. Traish, professor of biochemistry and urology at Boston University School of Medicine, the study took a look at the measured outcomes of a large cohort study involving older men around the ages of 50 to 70 being treated for benign prostate hyperplasia (BPH) — a condition caused by the increased production of prostate cells that restricts the flow of urine between the bladder and urethra.

Specifically, the authors looked at 470 men who were treated with finasteride and 230 men who were treated with tamsulosin. The groups were followed up with for 45 months, with measurements taken regularly of plasma testosterone levels and sexual function via the international index of erectile function (IIEF-EF) questionnaire.

"Long-term treatment with finasteride therapy is associated with worsening of erectile dysfunction (ED) as shown by the significant decrease in the IIEF-EF scores in men treated with finasteride," the authors concluded. "No worsening of ED was observed in men treated with tamsulosin."

Even worse, for many men, these side-effects didn’t resolve with continued finasteride use, eventually contributing to a drastic drop in testosterone production altogether, known as hypogonadism. There were no changes in testosterone levels for the tamsulosin group.

As the researchers note, there has been some debate about how lasting the known side effects of erectile dysfunction truly are when taking finasteride, part of a class of drugs known as 5α-reductase inhibitors. These drugs are often used to reduce the rate of testosterone being converted into dihydrotestosterone, a more potent sex hormone whose overproduction has been linked to BPH and male pattern baldness.

Tamsulosin, an alpha blocker that relaxes muscles in the bladder and prostate to reduce symptoms of BPH has also been linked to some sexual dysfunction among men, but it seems these side-effects are relatively fleeting compared to finasteride.

Though both classes of drugs can be effective for mild to moderate BPH. the authors believe that a change in how clinicians discuss BPH treatment options is in order, especially considering that as many as 80 to 90 percent of men will develop some form of BPH as they approach their 70’s, according to a 2005 review in Urology.

"Since sexual function is considered an integral part of overall health, it is important that physicians are aware of the adverse side effects of this class of drugs on human health in general and on sexual function in particular," said Dr. Traish in a statement released by the university. "Our study emphasized that the effect on erectile function is a serious concern and needs to be considered more carefully."

Source. Traish, A, Haider K, Doros G, et al. Finasteride, not tamsulosin, increases severity of erectile dysfunction and decreases testosterone levels in men with benign prostatic hyperplasia. Hormone Molecular Biology and Clinical Investigation. 2015