The yohimbe tree is native to the West African nations of Nigeria, Cameroon, Equatorial Guinea and Gabon. Traditionally, West Africans used yohimbe bark as an aphrodisiac. The active ingredient in yohimbe tree bark is yohimbine. In the U.S., extracted and purified yohimbine is available by prescription. Non-prescription yohimbe bark dietary supplements are not standardized. Despite package labeling, the actual yohimbine potency of over-the-counter yohimbe bark products will vary from company to company. Consult your doctor before taking yohimbe bark or other yohimbine-containing supplements.
Effects on the Body
Yohimbe's active ingredient works by blocking the alpha-2 adrenergic receptors. This blocking action gives yohimbe its positive and negative effects on the cardiovascular, respiratory and central nervous system functions. Alpha-2 receptors normally respond to the body's release of norepinephrine and epinephrine. Where norepinephrine causes dilation of blood vessels, yohimbe causes constriction. This same mechanism is responsible for yohimbe's benefit in male erectile dysfunction. Yohimbine is also a Monoamine oxidase inhibitor. Monoamine oxidase is an enzyme which deactivates neurotransmitters such as epinephrine and norepinephrine. Monoamine oxidase also deactivates the dietary amino-acid tyramine which has adrenergic effects. This process helps maintain optimum levels of adrenergic stimulants in the body. MAOIs block this enzyme and epinephrine and norepinephrine levels rise. This effect can be beneficial. MAOIs make effective anti-depressive medications; however, high adrenergic stimulant levels can raise heart rate and blood pressure to deadly levels.
Yohimbine can interact with blood pressure medications and decrease their effectiveness. The blood pressure medication clonidine works by stimulating alpha-2 receptors. Yohimbine directly blocks clonidine's actions. In addition, yohimbe supplementation along with the ingestion of food or drink containing caffeine or tyramine may result in dangerously high blood pressure. Paradoxically, in high doses, yohimbine may cause low blood pressure.
Effects on the Nervous System
Yohimbine containing products may have negative psychological and nervous system consequences. Yohimbine may induce mania in patients with bi-polar illness. A 1999, Connecticut Veterans Administration Hospital study published in Biological Psychiatry looked at what happened when four post-traumatic stress syndrome subjects took over-the-counter yohimbe supplements. The subjects all experienced worsened symptoms of anxiety, panic and PTSD. Normal doses of yohimbine may cause dizziness, anxiety, hyper-stimulation and nausea. Doses over 40 milligrams per day may cause hallucinations, unconsciousness and paralysis.
Non-Prescription Yohimbe Supplements
The Food and Drug Administration and biotechnology company Amgen collaborated on a one-year examination of dietary supplement-related calls to poison control centers. The results were published in the Journal of Medical Toxicology in 2008. Of 275 calls, 18 percent involved yohimbe containing products. Six of these involved yohimbe interactions with prescription drugs. Yohimbine is approved as a drug in the U.S., though in some European nations its use is banned or restricted due to its potential for harmful side effects. In Canada, the sale of non-approved yohimbine products without a prescription is banned. Germany's Commission E classified yohimbe bark as an unsafe herb due to its negative effects on the cardiovascular system.
Healthy individuals taking standardized yohimbe products at recommended doses with the knowledge and consent of their physician should rarely experience serious side effects. Patients with cardiovascular, nervous system or psychological should be under physician supervision before taking any yohimbe products.