“There were lots of reasons to think that it would work," Boston University researcher Matthew Spitzer, MD, says of the common practice of combining the two treatments. “It was surprising to me that it didn’t.”
The study, published in the Annals of Internal Medicine, was a good one and the largest of its kind, “but will it change practice? In my opinion, no," says urologist Jason Hedges, MD, PhD, of Oregon Health and Science University in Portland. He was not involved in the study.
“While low testosterone and [erectile dysfunction] ED can be related, they are separate issues, and I treat them as such,” says Michael Eisenberg, MD, who also was not involved in the study. “I don’t expect that treating low testosterone will improve ED, but it will likely improve libido and interest in sex," says Eisenberg, an assistant professor of urology at Stanford University School of Medicine.
“There is no benefit to adding testosterone to [Viagra]," Spitzer says. He notes, though, that every case is different. “Treatment is a highly individual situation, and this study does not represent all men. If you benefit from both, you should be comfortable continuing this combined therapy.”
Testosterone and Viagra
Spitzer's team studied 140 men with low testosterone for 14 weeks. All of the men took Viagra. Some also received testosterone gel, while others got a placebo.
During the study, the men reported how often they had sex and rated their sexual satisfaction, sexual desire and orgasms, and their ability to achieve and maintain an erection.
In every category, both groups had similar scores. On average, the men’s erectile function improved, with or without testosterone.
Treatment for the men in the study was “not a complete cure, but the improvements were substantial,” Spitzer says.
The study, Spitzer says, also reminds us that we don’t yet know all the ways in which drugs like Viagra work. One surprising discovery, he says, is that Viagra (sildenafil) appears to increase testosterone levels somewhat.
“Prior to this investigation, I had not thought of sildenafil as a drug that would raise testosterone,” says Spitzer. “This raises a lot of questions. It’s difficult to say why this happened, and I’m going to look into it in the future.”
When a patient has ED, Hedges says he always tests for low testosterone. If it proves to be low and the patient has other symptoms of low testosterone, the first thing he often prescribes is testosterone replacement therapy.
“Testosterone seems to raise or turn on signaling pathways that are important for erections,” says Hedges. “What’s common is to try testosterone and then add [Viagra or another ED drug] if you need it. Most of the time, testosterone won’t fix everything.”
Hedges and Spitzer report no disclosures related to the study. Eisenberg discloses receiving a drug company grant to study the association between testosterone and health.