A new testosterone nasal gel raises men's low testosterone levels to normal with few side effects, researchers report, adding that the treatment also strongly improved men's erectile function and mood.
Testosterone products applied to the skin carry the risk of transferring some of the drug to others who come into close contact.
In contrast, the new formulation sends testosterone directly into the nostril.
The product comes in a multiple-dose pump dispenser that administers a specified amount of testosterone gel (5.5 milligrams) inside each nostril.
"The unique delivery system makes this a convenient and easy-to-use, self-administered form of testosterone to treat adult males with hypogonadism (low testosterone)," said lead investigator Alan Rogol, professor emeritus at the University of Virginia, Charlottesville.
"Also important is that intranasal testosterone minimises the risk of unwanted secondary exposure of testosterone to women or children," Rogol said.
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The US Food and Drug Administration (FDA) has approved the medication, now called Natesto, making it the only FDA-approved nasal testosterone replacement therapy, according to Trimel Pharmaceuticals, its manufacturer.
The phase 3 clinical trial evaluated the effectiveness and safety of the testosterone nasal gel in 306 men with low testosterone.
Men used the treatment for 90 days in both nostrils either twice a day (228 men) or three times a day (78 men) as randomly assigned to find the most effective dose.
After 90 days of treatment, the average testosterone concentration in the blood was in the normal range for 90 percent of men who used the nasal gel three times daily, compared with 71 percent of men using it twice a day.
The manufacturer's recommended dosing is now three times a day in each nostril, for a total daily dose of 33 mg.
No serious medical problems related to the medicine occurred in either dosing group.
"These results indicate that testosterone nasal gel is an effective and practical alternative to other available testosterone replacement therapy products," Rogol said.
The results of phase 3 clinical trial were presented at the Endocrine Society's 97th annual meeting in San Diego, California, this week.