Materia Medica

Pausinystalia yohimbe   Rubiaceae.  The common name is yohimbe.

The yohimbe tree grows in West Africa, especially the French Congo and the Camerrons.  Local tribal people used the bark as a stimulant and aphrodisiac for ritual purposes.  It was once used by traditional medicine to treat angina and hypertension.

Native to West Africa, yohimbe grows in jungle forests at low altitudes.  It is a large tree, up to 40 feet tall with large oblong and oval leaves.  It has winged seeds.

The bark is the part used.  It is available in bulk herb, hydroalcoholic extract, combined with other ingredients in capsules and pills

The bark of the yohimbe tree contains about 6% of the alkaloid yohimbine.  Yohimbine is classified as an alpha-2-adrenergic receptor antagonist.  This results in an increase of norepinephrine that produces both a stimulant effect and an increase in autonomic nervous system activity.  Most of the studies have been done with yohimbine rather than the crude drug.  The yohimbe bark does, however, have a strong reputation for being an aphrodisiac and is used for that on the popular herb market.

Yohimbine is used to treat impotence or erectile dysfunction and has shown moderate success in numerous clinical trials.  It has a success rate of 34 to 43% improvement erectile functioning compared to a placebo.^1,2,3,4,5,6   A small study suggested it may be helpful for sexual side effects induced by serotonin reuptake blockers.⁷  It apparently takes two to three weeks for the full effects of the yohimbine to be experienced.⁸  Although yohimbine is considered to have a high-risk to benefit ratio, there were very few side effects reported in these studies even up to doses of 43 mg. per day.⁹   Herbal lore considers yohimbe a sexual stimulant for women, however, the only study with women was inconclusive.¹⁰

Yohimbine raises blood pressure and heart rate.¹¹  It increase salivary secretion.¹²  It is reported to be an inhibitor of monoamine oxidase and to have a weak calcium channel blocking effect.¹³

The bark of yohimbe contains about 6% yohimbine, as well the other alkaloids of ajmaline, allo-yohimbine, corynantheidine, corynantheine, dihydrocorynantheine, pseudoyohimbine, quebrachine, and tetrahydromethylcorynanthein.  It also contains tannins.¹⁴

The standard dose of yohimbine is 5-20 mg per day, with some reports that up to 43 mg may be helpful.  Yohimbine has a bell-shaped dose-response curve in animals and may in man, so you may lower the dosage if desired results are not attained.¹⁵  The suggested dose for yohimbe bark is 3 to 6 gm.¹⁶

It is contraindicate in schizophrenia, bipolar depression, anxiety disorders, high blood pressure, liver disease, kidney disease, pregnancy, and prolonged use.¹⁷  Possible side effects include nervousness, anxiety, irritability, dizziness, headache, sweating, hyper or hypotension, tachycardia, increased motor activity, psychosis and hallucinations.  There has been one report of a serious allergic reaction¹⁸.  It may have a weak MAO-inhibiting effect and precautions should be taken with diet and drugs.

Hypertension may occur with yohimbine and tricyclic antidepressants such as imipramine.  The toxicity of yohimbine, due to its alpha-2-adrenoceptor antagonism is increased by phenothaizines such as chlorpromazine, as well as reversal of hypotensive effects of clonidine and similar antihypertensives.¹⁹