Skin patches impregnated with drugs can help veteran smokers quit, queasy sailors avoid motion sickness and middle-aged women get relief from menopausal symptoms.
Now there's the testosterone patch.
The patch was initially designed for men with abnormally low hormone levels as a result of testicular surgery, pituitary gland tumors or other conditions.
But eventually, the patch might be prescribed to combat the effects of age-associated hormonal decline, including diminished sex drive, fatigue and decreased muscular strength.
One recent Oregon study suggests that the patch can boost hormone levels in the elderly enough to match those of 25-year-olds. But experts emphasize that much more study is needed before such widespread use is warranted.
ALZA Corp., one of two companies manufacturing a patch, has asked the FDA for approval to market its Testoderm patch for men with abnormally low testosterone levels, says Laura Mills, a spokeswoman for the Palo Alto-based company.
(About 200,000 to 400,000 younger men have abnormally low testosterone levels in the United States, according to ALZA estimates.)
And Theratech Inc. of Salt Lake City is completing clinical studies and expects to file for FDA approval in 1994, says Dinesh Patel, its chief executive.
The patch works by releasing the hormone gradually to maintain consistent blood levels of testosterone, which is naturally produced by the testes to stimulate bone and muscle growth along with male sexual development.
Proponents of the patch say the trans-dermal delivery route is superior to currently available treatment methods--injections or pills--partly because it keeps blood levels much more stable.
The ALZA patch must be worn on scrotal skin to ensure that sufficient amounts of the drug get into the blood stream, says Linda Atkinson, an ALZA scientist. That skin is more permeable than in other areas.
Theratech's patch can be worn anywhere on the body, says Patel, because of "penetration enhancers" within the patch. Patches from both companies are usually worn for 24 hours and then replaced.
"The majority of men treated with this patch achieve normal levels of testosterone," says Atkinson. "Their sense of well-being and energy level return to normal."
* In one ALZA-supported study of patch use published in the Journal of Clinical Endocrinology and Metabolism, all 10 men treated for abnormally low testosterone levels had an increase in testosterone blood levels, eight of them to normal range. Of those, seven said their symptoms were corrected by the treatment.
In the ALZA-sponsored studies, men were monitored for prostate cancer, and no increase was found in the treated men, Atkinson says.
* In Theratech-sponsored clinical trials, testosterone levels have increased to normal in 100% of the 50 men studied, says Patel. All had non-age related low testosterone.
Recently, researchers have begun focusing on patch use in normal older men:
* Thirty men, ages 60 to 75, who wore a testosterone patch for 16 hours a day had a substantial increase in blood levels of the hormone, says Dr. Eric Orwoll, associate professor of medicine at Oregon Health Sciences University in Portland, who reported his research earlier this year at an Endocrine Society meeting.
"Their testosterone levels were similar to those of younger men, about age 25," says Orwoll.
The 30 men in the control group who wore a placebo patch showed no such increase.
* In another study, Dr. Peter Snyder, a professor of medicine at the University of Pennsylvania, is trying to determine if the patch can reverse the effects of diminished hormone levels, such as fatigue, decreased sex drive, reduced muscular strength and reduced bone mineral density.
He will enroll 100 normal men over age 65. Half will wear a testosterone patch and half will wear a placebo; no one will know which patch they receive.
Snyder will also study the patch in 30 men with abnormally low hormone levels.
The study will take about five years.
Testosterone replacement "is not as clear-cut as estrogen replacement," Atkinson says, partly because women's estrogen levels fall somewhat rapidly around menopause. Men's testosterone levels, in comparison, decline more gradually. And some men's testosterone levels decline very little, even with advanced age.
"We have seen 89-year-olds with the testosterone levels of normal younger men," Atkinson says. "What we know now is, when men get older, their testosterone levels fall, bone mineral density declines and muscle strength declines," Snyder says.
"It seems reasonable that reduced testosterone could be the cause of the simultaneous decline in both bone mineral density and muscle strength, but there is no proof that is the case."
Even if the hormonal decline causes the other declines, Snyder says, proof is needed that the changes are reversible. If so, research next needs to determine if the changes are preventable with earlier treatment.
It is also vital, Snyder says, to be sure that the supplementary hormone does not increase the risk of prostate enlargement, prostate cancer or other side effects.