Men who have failed treatment with sildenafil (Viagra) may respond to another phosphodiesterase inhibitor, vardenafil (Levitra), according to findings presented here May 18th at the American Geriatric Society Annual Meeting.

The trial was carried out internationally, including Canada, Europe, and the United States. The investigators looked at the effects for three different age groups, including men older than 65 years. The statistical analysis was carried out for the study patients as a whole, comparing the active drug to placebo. The study’s primary end point was erectile function domain score on a 1-30 point scale.

Enrollment criteria were four of six attempts at sexual intercourse that failed after taking Viagra according to package directions, failure after using 100-mg dose of Viagra, and the patient and his doctor had concluded Viagra was not working.

All men enrolled had moderate to severe erectile dysfunction, most with comorbidities. Forty percent had hypertension and about a quarter in each treatment arm had diabetes. The study excluded men with radical prostatectomy and men using nitrates or with unstable angina.

In the intent-to-treat analysis, 30% of the 229 men recorded their response to vardenafil as a return to normal; this included 26% of men older than 65 years. Of the 225 men on placebo, 6% recorded a response as a return to normal (P < .001).

“There is a fair [number] of patients who are nonresponders to Viagra,” said GlaxoSmithKline investigator Trish McBride, RN, MBA, who presented the poster. Studies have shown that some can be rechallenged with the same drug successfully, she said.

“I think we have good efficacy,” she said, “It’s a comparison to placebo, but based on criteria, those that did not respond to Viagra did [respond] to our drug.”

The research was funded by GlaxoSmithKline.