Yohimbe, known scientifically as Pausinystalia yohimbe, is an evergreen tree native to parts of West Africa. For hundreds of years, a bitter tea made from the bark has been employed as an aphrodisiac. In 1938, the alkaloid yohimbine, derived from yohimbe bark, was approved for use in treating impotence. Although yohimbine is the primary active constituent, the bark contains over 30 other pharmacologically active alkaloids. Despite the development of safer and more effective medicines for erectile dysfunction, powdered yohimbe bark and liquid extract remain popular alternative treatments. Consult your doctor before using any supplement containing yohimbe.
Constituents
Although yohimbine is responsible for much of yohimbe's therapeutic activity, it is possible that some of the other alkaloids present contribute to its overall effect. Corynantheine, dihydrocorynantheine, and ajmaline may act as sedatives or tranquilizers when taken in small doses. Yohimbine itself paradoxically acts as both a sedative and a stimulant. The ratios between these and other alkaloids, therefore, can have a profound effect on whether or not the yohimbe supplement you use will have a stimulating or sedating effect.
Pharmacology
While some yohimbe extracts are full-spectrum extracts, a number of extracts are almost entirely yohimbine. Extracts standardized according to yohimbine content are particularly prone to using yohimbine alkaloids almost exclusively in their formulations. Unlike whole extracts, these products in particular are more likely to produce stimulation and side effects related to increased sympathetic nervous system activity. Some people, however, find that both the whole herb and full-spectrum extracts cause an increase in gastroinstestinal side effects due to an increased sensitivity to the other alkaloids.
Pharmacodynamics
Yohimbine, an alpha-2-adrenoreceptor antagonist, increases parasympathetic nervous system activity while simultaneously increasing sympathetic nervous system activity. Since parasympathetic nervous system activity is required for the erection of genital tissue, it is believed that this is the mechanism by which yohimbe treats impotence. For this reason, MayoClinic.com still lists yohimbine as a treatment for psychogenic impotence despite the high incidence of side effects. Its direct effects on adrenergic receptor sites throughout sacral region nerves may also account for increases in genital sensitivity and a decrease in the time needed to achieve orgasm. Extracts that are high in yohimbine relative to other alkaloids may have an increased incidence of these side effects.
Drug Interactions and Contraindications
Unlike most pharmaceutical treatments for erectile dysfunction, supplements containing yohimbe can cause high blood pressure. For this reason, do not take yohimbe if you are suffering from heart disease, kidney disease or hypertension. According to the National Center for Complementary and Alternative Medicine, yohimbe's central nervous system stimulant properties can elevate heart rate or cause headache, anxiety, nausea, dizziness, vomiting or insomnia. Combining yohimbe with some prescription medications, particularly antidepressants or stimulants, may be fatal. Due to the risk of serious side effects and drug interactions, you should talk to your doctor before taking any products containing yohimbe bark or extract.
References
- Mayo Clinic; Erectile Dysfunction; September 2010
- National Center for Complementary and Alternative Medicine; Yohimbe; July 2010
- Sloan-Kettering; Yohimbe; March 2011
- United States Department of Agriculture; Chemicals in: Pausinystalia johimbe (K. SCHUM.) PIERRE (Rubiaceae) -- Yohimbe
- National Toxicology Program Study Reports; Yohimbe Bark Extract / Yohimbine; November 1999
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