Men who take prescription drugs for erectile dysfunction (ED) may be at increased risk for sexually transmitted diseases, according to an observational study in the Annals of Internal Medicine.

U.S. researchers used insurance benefits databases to assess STD rates and ED drug use among some 1.4 million men older than 40. They found that men who used ED drugs were more likely than nonusers to be treated for STDs both in the year before filling their first ED drug prescription (odds ratio, 2.8) and in the year afterward (OR, 2.7). The increased risk was mainly driven by higher rates of HIV and chlamydia.

An editorialist notes the study’s limitations but finds the results “both believable and alarming.” He concludes that it’s “critical that all ED drug prescriptions be accompanied by assessment of STD risk and counseling about safe sex” — although “routine STD testing of men requesting ED drugs may not be [warranted].”