March 2, 2000 (Atlanta) -- The FDA this week approved the first testosterone gel for treatment of men with low testosterone levels. The gel, called AndroGel, is applied once daily to the shoulders, upper arm, and/or abdomen.
"This is a quite convenient way of delivering testosterone in a dose-related fashion. The more you put on, the higher the testosterone," Ronald S. Swerdloff, MD, tells WebMD. Swerdloff is chief and professor of medicine, division of endocrinology, at Harbor-UCLA Medical Center in Los Angeles. He was the lead investigator of AndroGel on behalf of the manufacturer, Unimed Pharmaceuticals Inc.
"The testosterone gel has several advantages over the [currently] available delivery systems," Swerdloff says. Unlike injections, the gel does not cause discomfort, and it provides a constant level of testosterone. The oral versions of testosterone are synthetic and may be damaging to the liver, while transdermal patches often have problems with adhesiveness.
Testosterone, one of a class of hormones known as androgens, is responsible for the development of the male sex organs and for the maintenance of secondary sex characteristics, including development of facial and pubic hair, vocal cord thickening, and alterations of body musculature. Low testosterone, a condition called hypogonadism, affects approximately 4-5 million American men and is linked to diminished interest in sex, impotence, reduced lean body mass, decreased bone density, and lowered mood and energy levels.
AndroGel is a colorless gel containing 1% testosterone. It is applied daily to clean, dry skin; the gel dries within a few minutes and is absorbed into the skin, which serves as a reservoir, providing sustained delivery to the bloodstream for up to 24 hours. After applying the gel, patients should immediately wash their hands to avoid exposing others to the medication. The gel should not be used on women, and pregnant women should avoid contact with the application sites of the gel on men, as it could harm the fetus.
In the female partners of men using AndroGel, 15 minutes of vigorous skin-to-skin contact increased testosterone in the women to twice their ordinary levels. When a shirt was worn to cover the gel-application site, transfer of testosterone to the women was prevented.
"In none of the partners of the individuals who were treated with testosterone were there any significant clinical problems," Swerdloff tells WebMD. "Because there is a potential for testosterone transfer, the recommendation is that patients shower before intimate contact or wear a shirt over the area to which the drug is applied. The testosterone is driven into the skin, so showering doesn't alter the effectiveness of the testosterone."
To assess the effectiveness of AndroGel, researchers studied 227 men with low testosterone levels. The men received either AndroGel in varying doses, or testosterone through a skin-patch delivery system. After 60 days, their blood levels of testosterone were checked and the doses were adjusted. Of the 129 men who were appropriately adjusted, 87% achieved normal levels of testosterone that were maintained for the remaining three months of the trial. In this and other trials, side effects were moderate but infrequent -- mostly skin reactions to the gel, including acne; prostate and urinary problems; and swelling.
"We were able to put the testosterone into the normal blood range in the majority of the people. It's simply a matter of adjusting the amount of gel that's applied. So everybody could be treated once a proper dosage [is] determined," Swerdloff says. The manufacturer recommends checking the blood two weeks after starting.
"The positive effects were on sexual drive and on mood," Swerdloff says. "People had less depressive symptoms. There was an improvement in the lean body mass and muscle strength. ... It was surprising to us that within six months of treatment, there was a significant increase of bone mineral density."
Swerdloff tells WebMD that there are many potential applications for testosterone. It is being studied in combination with other hormones as a male contraceptive. Many researchers are looking at giving androgen replacement therapy in men over 65. Testosterone may also one day be used in women to improve libido, or added to conventional hormonal therapy to help improve bone mineral density. AndroGel is only approved for men and has not been studied in those over age 65.