TORONTO—Chronic use of 5-alpha-reductase inhibitors is associated with mild decreases in sperm count and semen volume, but these recover when men stop taking the drugs, according to data presented here at The Endocrine Society’s annual meeting (ENDO 07).


The effect on fertility is unknown, but use of these drugs should be evaluated when treating men with unexplained oligospermia, researchers say.

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They conducted a randomized, double-blind, placebo-controlled study in 99 healthy men with a mean age of 35 years (range 18-52 years). The men were randomized to treatment with either dutasteride 0.5 mg (33 subjects), finasteride 5 mg (34 subjects), or placebo (32 subjects). Twenty-three men withdrew from the study; 29 men in the dutasteride group, 22 in the finasteride group, and 25 in the placebo group completed the 52-week treatment phase of the study.


All the men provided semen samples in triplicate over two weeks during the baseline phase before drug administration, and again after 26 and 52 weeks of treatment.  Samples were also collected 24 weeks after treatment ended.


Total sperm counts decreased by 28.6% and 34.3% in the dutasteride and finasteride groups, respectively, at week 26, and by 24.9% and 16.2% at week 52 compared with the placebo arm. Semen volume decreased by 24% and 21.1% in the dutasteride and finasteride groups, respectively, at week 26 and by 29.7% and 14.5% at week 52. Semen concentration decreased by 12.9% and 21.5% in the dutasteride and finasteride groups at week 26 but only 3.2% and 7.4% at week 52, according to investigators.


In addition, sperm motility was significantly reduced in both groups by 6%-12%. Sperm morphology was unaffected in both groups.


Investigator John Armory, MD, associate professor of medicine at the University of Washington in Seattle, pointed out that three men (5%) had decreases in their total sperm concentrations that were low enough for them to be at increased risk of infertility.


“For most men, these drugs are safe in terms of sperm production and are not associated with any increased risk of infertility, but for a small subset of men there were significant decreases in sperm concentrations,” Dr. Armory said.


All men in the treatment arms showed partial or nearly complete recovery in their semen parameters after drug discontinuation.


“If a practicing urologist is seeing someone with a low sperm count and he is on one of these medications, then he may want to consider stopping the medicine to see if the sperm counts improve,” Dr. Armory advised.