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CHICAGO -- Intracavernosal platelet-rich plasma (PRP) injections were no better than placebo for treating mild-to-moderate erectile dysfunction, a found.

At 1 month after the second round of injections, no significant difference was seen between the PRP and placebo groups for the study's primary endpoint, the percentage of men attaining a minimum clinically important difference (MCID) in erectile function (58.3% vs 53.6%, respectively, P=0.730), reported Braian Ledesma, a research scholar at the Miller School of Medicine at the University of Miami.

Among the 61 men randomized, mean scores on the International Index of Erectile Function–Erectile Function domain (IIEF-EF) increased for both groups by that time point, from 17.4 at baseline to 21 with each round of 5-mL PRP injections, and from 18.6 to 21.6 with placebo.

No significant differences were seen between groups at 3 and 6 months as well, according to findings presented at the American Urological Association (AUA) annual meeting and published in the .

"This is the first human study in the U.S. to test safety and efficacy of PRP for erectile dysfunction," Ledesma said during a late-breaking abstract session at the meeting. "PRP appears to be safe for erectile dysfunction, but not more efficacious than placebo."

The moderator of the AUA session, Hossein Sadeghi-Nejad, MD, director of the Center for Male Reproductive Medicine at Rutgers New Jersey Medical School in Newark, called the study "very important ... because there is so much going on with PRP in so many clinics."

He noted that there are data, particularly in the orthopedic literature, showing that PRP appears to work. He asked AUA study co-author Ranjith Ramasamy, MD, director of Reproductive Urology at the Miller School, about the significance of PRP volume and surface site for these procedures.

"We pretty much followed orthopedic protocols on the amount of injections and surface area that gets injected and chose [the dose] based on what's been published before," Ramasamy said. "There are studies outside the U.S. showing in a randomized, double-blind fashion that this does work."

For example, a randomized involving 60 men with mild-to-moderate erectile dysfunction at 6 months showed a MCID in 76% of those who received two intracavernosal injections of PRP (10 mL), as compared with only 25% for a placebo group. In another of 31 patients with erectile dysfunction associated with metabolic syndrome, 61% had improved IIEF-EF scores after three injections of intracavernosal PRP.

"Maybe these studied different patient populations ... maybe they used a different PRP machine," Ramasamy said. "But we don't see it."

In their paper, the researchers explained that PRP contains multiple growth factors involved in "complex healing processes," including platelet-derived growth factor, transforming growth factor-beta, vascular endothelial growth factor, epidermal growth factor, insulin-like growth factor, and fibroblast growth factor.

These properties have made PRP "an attractive treatment for orthopedic injures and sports medicine," the team wrote, with some studies suggesting it may also be beneficial in erectile dysfunction.

However, "despite the hypothesized mechanisms and benefits that may make PRP an attractive treatment, there is remarkably little clinical evidence supporting its use in ED [erectile dysfunction]," Ledesma, Ramasamy, and co-authors observed. "Even without supporting data, numerous clinics in the largest metropolitan areas of the United States are charging patients for PRP treatments for ED."

The current study included men ages 30 to 75 with mild-to-moderate erectile dysfunction (defined as IIEF-EF scores of 11-25) for at least 6 months, normal testosterone levels, and hemoglobin A1C levels less than 9%.

Patients in the double-blind trial were randomly assigned to receive two rounds of PRP injections (5 mL each round, delivered as two 2.5 mL injections) or placebo, separated by 28 days. The primary outcome was the percentage of men meeting MCID at 1 month following the second round of injections; MCID was defined as an increase of 2 points on the IIEF-EF for mild erectile dysfunction (IIEF-EF 17-25) and an increase of 5 points for moderate erectile dysfunction (IIEF-EF 11-16).

Secondary outcomes were changes in IIEF-EF scores, changes in penile vascular parameters, and adverse events (AEs) at 3 and 6 months.

Of the 61 patients in the study, 28 had PRP injections and 33 received placebo; investigators had completed 1-month data for 24 men receiving PRP and 28 receiving placebo. There were no differences in baseline demographics or characteristics between the two groups, except that more in the placebo group were prediabetic despite having similar median A1c levels.

On a scale of 1 to 10, the mean pain score with the first injection was 3.7 for patients in the PRP arm and 3.5 in the placebo arm, and mean pain with the second injection was 4.1 for the PRP arm versus 4.0 in the placebo arm. There were few AEs reported.

The authors acknowledged several limitations to the study, including the possibility that the protocol of two injections 1 month apart, isn't optimal. "It is possible more injections or a different interval between injections may yield greater changes in IIEF-EF," the team suggested.