Dr. Ridwan Shabsigh, associate professor of urology at Columbia University College of Physicians & Surgeons and director of the New York Center for Human Sexuality at NewYork-Presbyterian Hospital/Columbia was the lead investigator in the study, which is published in the August issue of the Journal of Urology.
"Our data support the potential benefits of a combination therapy with testosterone gel for men with erectile dysfunction and low testosterone who find sildenafil by itself ineffective," said Dr. Shabsigh. "When assessing erectile dysfunction, doctors and patients should consider using a simple blood test to determine if low testosterone is a contributing factor. If the root cause is low testosterone, sildenafil alone won't fix the problem."
It is estimated that four to five million American men have low testosterone. Furthermore, low testosterone, also called hypogonadism or "low T," affects about one in 10 men between the ages of 40 and 60. Low testosterone may lead to decreased libido, erectile dysfunction, osteoporosis, reduced lean body mass, depressed mood and fatigue.
Sildenafil enhances the effects of nitric oxide, a chemical in the body that allows increased blood flow to the penis during sexual stimulation. "Research suggests nitric oxide may be dependent on testosterone to function properly," said Dr. Shabsigh. "While further studies are needed, this concept may explain why testosterone replacement therapy could help hypogonadal men who do not respond to sildenafil."
In the trial, 75 hypogonadal men (18 to 80 years old) were randomized to testosterone gel plus sildenafil versus placebo plus sildenafil. Participants were in a stable heterosexual relationship. Ninety-one percent had experienced erectile dysfunction for at least one year prior to the study. All participants had testosterone levels in the low to low/normal range (<400ng/dL) and had failed to respond to 100mg doses of sildenafil, based on questions from the International Index of Erectile Function (IIEF) scale.
Analysis of 70 men at four weeks found the population randomized to receive a daily dosage of 5mg testosterone gel in addition to a 100mg sildenafil (n = 37) taken as needed, had a significantly improved response to treatment, when compared to those on 100mg sildenafil plus a placebo (n = 33). Results of the Erectile Function Domain, Orgasmic Function Domain, Overall Satisfaction and Total Score on the IIEF were used to compare the groups. For Erectile Function Domain, the men receiving testosterone gel reported an average increase double those receiving a placebo, with a 34 percent and 17 percent improvement from baseline, respectively. On average, participants in the testosterone gel group reported a 28 percent increase from baseline in Orgasmic Function Domain compared to a 4 percent improvement in the placebo group, after four weeks of treatment. Overall Satisfaction improved 32 percent in the testosterone gel group, compared to 10 percent in the placebo group. The results at eight and twelve weeks showed a trend in favor of testosterone gel compared to placebo, but no statistical significance.
Dr. Shabsigh is the author of "Back to Great Sex: Overcome E.D. and Reclaim Lost Intimacy," a book developed to help men with erectile dysfunction communicate effectively with their physicians.
* Manufactured by Pfizer Inc.
** Manufactured by Unimed Pharmaceuticals, Inc., a Solvay Pharmaceuticals, Inc. company