Older men are not the only ones using impotence pills. New research shows the fastest growing segment of Viagra (sildenafil) users is men ages 18 to 55.

The study by Express Scripts, a prescription drug tracking firm, examined Viagra use among 5 million insured males, ages 18 and older, from 1998 to 2002. The fastest growing segment of Viagra users was men under 55. In men 18 to 45 years, use increased 312 percent. In men 46 to 55 years, use increased 216 percent.

            

Overall, use of Viagra increased 84 percent in the study group, with men older than 56 years receiving the majority of prescriptions. In addition, researchers found Viagra use for a medical reason declined in all age groups. They say these findings imply increased use of Viagra for enhancement and recreation.

The authors say that prescription benefit plans of erectile dysfunction drugs vary from unrestricted coverage to no coverage, and the large increase in Viagra users could be bad for insurers. ''Already concerned with the impact Viagra has had on their pharmacy budgets, health plan sponsors now face the prospect of increased use among a younger, healthier generation of patients,'' says Tom Delate, Ph.D., lead author of the study.

''In addition, marketing approval of other erectile dysfunction drugs, such as Levitra (vardenafil) and Cialis (tadalafil), will likely increase utilization of such drugs,'' Delate concludes.