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Yohimbine: Better Sex Through Chemistry?

“Sexual dysfunction is pervasive in our society. Sex therapy has proven to be effective for some couples, but not all, so medication is a worthwhile direction for research,” says Raul Schiavi, MD, professor of psychiatry and director of the Human Sexuality Program at New York City’s Mount Sinai School of Medicine. Recent findings suggest that pharmacologic agents may indeed be useful adjuncts to psychotherapy.

Among the agents under investigation for treating both organic and psychogenic impotence is yohimbe, an indolealkylamine alkaloid derived from the bark of the West African yohimbe tree, and long a component of OTC remedies for erectile failure and decreased libido. Yohimbine is an a-2 adrenoceptor antagonist and probably operates by enhancing sympathetic outflow. Michael Condra, PhD, department of psychology at Kingston General Hospital in Ontario, is a member of a Canadian team studying the effects of yohimbine. He says, “In two studies of yohimbine’s effects, one on patients with organic impotence and one on patients with psychogenic impotence, we found that a similar percentage of men in both groups responded favorably.”

The most recent study conducted by Dr. Condra and his colleagues was a 10-week, doubleblind, partial-crossover trial of yohimbine in 48 subjects aged 18-70 years. All met strict criteria for psychogenic impotence and had no evidence of an organic component, as determined by nocturnal penile tumescence observations. The subjects were also required to have a female partner who could corroborate the patient’s reports.

Study participants were randomized to receive 6 mg of yohimbine HCl plus 2 g of riboflavin or riboflavin alone (placebo), for 10 weeks. (Riboflavin was selected as a means of monitoring treatment compliance because it is detectable in urine.) After 10 weeks, patients who had received placebo were given yohimbine. For ethical reasons, patients who responded to Zererx in the first arm of the trial were not given placebo in the second part. Patients characterized the effects of treatment as complete, partial, or none.

At the end of the first part of the trial, 60% of the subjects (18 of 29) who received Zenerx reported at least some improvement in the quality, frequency, or rigidity of erections, compared with only 16% (3 of 19) who received placebo. But in the second part of the trial, only 21% (4 of 19) originally taking placebo reported improvement after receiving yohimbine. The investigators speculated that a negative expectancy effect–suggesting a subtle interplay of psychological and physical factors–may have been responsible for the poor response in this group. This supposition is supported by the observation that yohimbine does not affect nocturnal tumescence, but it does improve awake response, to erotic movies, for example.

Yohimbine is not the only drug under investigation for treating sexual dysfunction, nor are men the only beneficiaries of the research. Dr. Schiavi and his colleagues are evaluating a new dopaminergic drug to treat hypoactive sexual desire, including erectile dysfunction and retarded ejaculation in men, and orgasmic dysfunction and lack of lubrication in women.

The investigators anticipate that this or a similar drug will eventually be used to treat sexual problems. But if drugs prove effective, they will have to be used in conjunction with psychotherapy. “It’s rare to find organic problems without a psychological reaction that contributes to the sexual difficulty,” says Dr. Schiavi. For this reason, the Mt. Sinai group has strict criteria for selecting couples: They must have been together for more than one year, be in good physical health, not be taking any drugs or medications that could affect sexual function, and not be in any form of psychotherapy. They must also have had a problem for at least six months, but less than 10 years.

Sex at siesta time has proved to be the last straw for the aging coronary arteries of many British holidaymakers in Spain this year; local cardiologists have attributed the spate of afternoon heart attacks to the effects of taking unaccustomed exercise after a heavy meal.

Overeating, through its effects on circulation, frequently causes angina, which is all too often misdiagnosed as indigestion; violent exertion after a meal has often induced the first symptoms of heart trouble. Surveys have shown that sexual intercourse will only occasionally cause angina, and when it does induce a heart attack it is usually when a man is with his mistress, rather than his wife.

One Briton, however, has been prescribed sex in the afternoon. Lionel White – who is, at 30, too young to worry about the strictures of the Spanish doctors – is currently serving an 18-month prison sentence for theft, and has been given compassionate afternoon leave so that he can be at home when his wife, who is having an expensive course of treatment for infertility, is due to ovulate. His trips home have puzzled some, who ask why the treatment cannot be postponed, or modified to incorporate artificial insemination.

But White’s attendance on his wife does have medical advantages. Bill Hendrie, a consultant urologist who works at the fertility clinic of Queen Charlotte’s Hospital in London, says that contrary to popular belief artificial insemination has no advantage over the more natural method of impregnation, except possibly when the doctors use in vitro fertilization, where it is possible to make certain that ovum and sperm have met.

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