Yohimbe is a tree that grows throughout the African nations of Cameroon, Gabon and Zaire. (A similar plant in South America is called Quebracho). For centuries, natives from these areas have ingested both the crude bark and purified compound as a tonic to enhance sexual prowess and as an aphrodisiac. The bark has been smoked as a hallucinogen and has been used in traditional medicine to treat angina and hypertension. The herb is a sensual stimulant for healthy men and women. Today, doctors prescribe an extract from the tree to treat organic impotence.
Yohimbe is an herb derived from the inner bark of the yohimbe tree which grows wild throughout Africa. Long considered an effective aphrodisiac, able to stimulate sexual desire and performance, Yohimbe has been available by prescription as a pill. Recently Yohimbe containing products have become popular as over the counter herbal preparations. The active component of Yohimbe bark is yohimbine, an alkaloid monoamine oxidase (MAO) inhibitor that blocks adrenergic receptors. This leads to an increase in dilation of blood vessels and a lowering of blood pressure. This enlargement of blood vessels, particularly in the sexual organs, is the generally accepted explanation of the physiological effects of the herb. Yohimbe also seems effective in elevating mood and reducing depression and anxiety, further contributing to its aphrodisiac activity.
The active compound in yohimbe, an alkaloid called Yohimbine, functions as a monoamine oxidase (MAO) inhibitor to increase levels of the neurotransmitter, norepinephrine. Yohimbine also acts as a central nervous system stimulator, where it blocks specific receptors (alpha-2 adrenergic receptors) and may increase energy levels and promote fat oxidation. In addition to these effects, yohimbe can also dilate blood vessels – making it a potentially useful treatment for erectile dysfunction and some forms of impotence in men. Because of the MAO inhibition, yohimbe is occasionally recommended as a treatment for mild depression – but St. John's wort has much better clinical support for effectiveness and safety.
Yohimbe is promoted as an aphrodisiac/sexual function enhancer and as a thermogenic agent in some weight loss products. The major active agent in yohimbe is the alkaloid yohimbine. Authentic yohimbe bark is reported to contain up to 6% total alkaloids of which 10-15% is yohimbine (0.6-0.9%). Yohimbine is described as an alpha-2-adrenergic receptor antagonist, a class of drugs that modify the activity of nerve receptors and therefore can change a variety of physiological parameters (1). By blocking these receptors, yohimbine acts as a potent vasoconstrictor and can raise blood pressure. There are varying reports on its efficacy in the treatment of erectile dysfunction; some show significant improvement (2,3,4,5) while others show no improvement above placebo (6,7,8). A recent review has stressed that yohimbine, as an "orphan drug" which cannot be patented, has never been studied in properly designed clinical trials (9). Typical dosages of yohimbine used in these studies were 30mg-100mg per day orally. Systematic reviews (3,4) of all the published studies generally confer a positive effect upon yohimbine, noting that side effects can occur but that the benefits of the product outweigh the risk.
For nearly a century, yohimbe has been used as an aphrodisiac and sexual enhancer - although no effect on human sex drive or performance has been adequately demonstrated. Yohimbine (the drug) has been evaluated in the management of erectile disorder in a few small studies, where it appears to have a modest therapeutic benefit over placebo (especially in "psychological" erectile dysfunction). Laboratory analyses (via chromatogram) of commercial yohimbine extracts, however, indicate that although many products contained measurable quantities of the alkaloid yohimbine, the vast majority are largely devoid of effective levels of the compound. Concentrations of yohimbine in commercial yohimbe products typically range from zero to almost 500 ppm (compared with over 7000 ppm in authentic yohimbe bark). Because yohimbe bark has been reported to contain up to 6% total alkaloids, 10-15% of which are yohimbine, it is likely that most supplements containing yohimbe also contain undeclared diluents. Because there are more effective and safe supplement remedies for increasing circulation to promote erectile function (arginine, cordyceps and ginkgo biloba), enhancing muscle strength (HMB and creatine) and weight loss (green tea, banaba leaf and gymnema) and relieving mild depression (SAM-e and St. John's wort), yohimbe is of limited value.