Moinpour's team studied data from a prostate cancer prevention study of more
than 17,000 men aged 55 and older.
The study lasted for seven years. When it began, the men completed a survey
about their sexual function.
Survey topics included the men's ability to have an erection when desired,
degree of satisfaction with sexual activities, change in sexual performance,
frequency of sexual activities, age, medical conditions, and smoking
Survey scores could range from zero to 100. Higher scores indicated worse
The men repeated the survey at least one other time during the seven-year
study. During that time, they were given either Proscar or placebo pills
without knowing the difference.
Proscar Study's Results
Proscar "increased sexual dysfunction only slightly and its impact
diminished over time," write Moinpour and colleagues.
Six months after the men started taking their assigned drugs, the survey
scores were about three points higher for the men taking Proscar. By the end of
the study, that gap narrowed to about two points.
Sexual problems can happen for many reasons. For instance, the researchers
note that getting older worsened survey scores by about eight points during the
study. That makes Proscar's impact look "small," write Moinpour and
However, the researchers note that the data only include men who stuck with
the study -- not those who quit taking their assigned drugs.
"Sexual dysfunction was often cited as the reason for dropping out,"
Moinpour's team notes, adding that there were more dropouts taking Proscar than
However, the researchers argue that dropouts probably didn't affect the
Proscar is made by the drug company Merck, which provided Proscar and the
placebo for the study. Merck also gave the researchers small grants to promote
study participation and adherence.
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