FWD 2 Expanded Commission E: Yohimbe bark

Herbal Medicine: Expanded Commission E

Yohimbe bark

Latin Name: Pausinystalia yohimbe
Pharmacopeial Name: Yohimbehe cortex
Other Names: johimbe

Overview

Yohimbe is a tall evergreen forest tree, reaching a height of 90 feet and width of 40 feet, native to southwestern Nigeria, Cameroon, Gabon, and the Congo. The material of commerce is collected in the wild in this same region (Bown, 1995; Keay, 1989; Leung and Foster, 1996; Reichert, 1997).

Yohimbe bark has traditionally been used in western Africa as a sexual aphrodisiac, especially in male erectile disorders, reportedly stimulating both erection and salivation. Medicinal use of yohimbe bark reached Europe in the 1890s. The majority of pharmacological data is on one of its isolated constituents, the indole alkaloid yohimbine, rather than on whole bark preparations (Bown, 1995; Duke, 1997; Grasing et al., 1996; Leung and Foster, 1996). Yohimbine is also found in related trees (Pausinystalia macroceras and P. tillesii) as well as in Indian snakeroot (Rauwolfia serpentina (L.) Benth) and quebracho (Aspidosperma quebracho-blanco). In Africa, P. lane-poolei (pamprana, igbepo) is also used therapeutically. A dressing of the ground bark is applied topically to yaws (an infectious tropical skin disease) and itching skin (Bown, 1995; Budavari, 1996; Duke, 1997).

In Germany, yohimbe bark is the subject of a negative (unapproved) monograph in the Commission E due to lack of data and safety concerns.In the United States, yohimbe bark is widely used in numerous aphrodisiac, athletic performance (as an alternative to anabolic steroids) and male sexual performance dietary supplements. The most commonly prescribed drug for functional impotence is yohimbine hydrochloride (e.g., Afrodex, Aphrodyne, Yocon, Yohimex, Yohydrol), which is often combined with other drugs, including strychnine, thyroid, and methyltestosterone (Leung and Foster, 1996; Tyler, 1993). The Merck Index reports its therapeutic category as an a-adrenergic blocker and mydriatic (causing pupillary dilatation), its use as a pharmacological probe for the study of a2-adrenoceptor, and its uses in veterinary medicine as an aphrodisiac and as an adrenergic blocking agent (Budavari, 1996).

No significant human studies on crude yohimbe bark or its whole extract have been conducted.Numerous studies, however, have investigated the actions of the isolated constituent yohimbine; for example, some pharmacokinetic studies have been performed in humans (Grasing et al., 1996; Owen et al., 1987) and human clinical studies have investigated its use for erectile dysfunction or male impotence (Morales et al., 1987; Reid et al., 1987; Riley, 1994). One study indicated that lower doses of yohimbine, given to patients who are fasting or eating a low-fat diet, may be more effective (Grasing et al., 1996).

There are a few studies showing that yohimbine is effective for some impotence, especially of vascular, diabetic, or psychogenic origins. It can improve the quality and staying power of erections, usually without increasing sexual excitement. The Commission E noted side effects, however, including dizziness, nervousness, and anxiety. To determine its therapeutic efficacy and evaluate the safety of yohimbine in regard to its specific use for erectile dysfunction, a systematic review and meta-analysis of randomized clinical trials was conducted (Ernst and Pittler, 1998). The authors found seven trials that fit the predefined inclusion criteria. Overall methodological quality of those studies was satisfactory. The meta-analysis demonstrated that yohimbine is superior to placebo in treating erectile dysfunction. Serious adverse reactions were infrequent and reversible. The authors concluded that the benefits seem to outweigh the risks. Therefore, yohimbine is considered to be a reasonable therapeutic option for erectile dysfunction (Ernst and Pittler, 1998). This conclusion is based not on the bark but on the isolated constituent yohimbine, which is available as a drug. A review of yohimbine and related yohimbe alkaloids details potential adverse effects and drug interactions (De Smet, 1997).

Though yohimbe bark is freely available in the United States in health and natural food stores, pharmacies, and by mail order, it should be used with caution. It is not recommended for excessive or long-term use and may potentiate pharmaceutical MAO-inhibitors. Its pharmaceutical derivative, yohimbine, can significantly increase blood pressure at oral doses of only 1520 mg (12 mg can induce a hypertensive crisis in patients taking tricyclic antidepressants), produce unpleasant digestive and central nervous system symptoms, and may potentiate hypotensive drugs. A dose as low as 10 mg can induce mania in patients with bipolar depression (Bruneton, 1995; De Smet and Smeets, 1994; Grasing et al., 1996; McGuffin et al., 1997; Osol and Farrar, 1955; Reichert, 1997; Roth et al., 1984). An analysis of commercial yohimbe products sold in the United States revealed that few products were found with any appreciable levels of yohimbine, raising concerns about the quality control of some of these products (Betz et al., 1995).

Description

Yohimbe bark consists of the dried bark of the trunk and branches of Pausinystalia yohimbe (K. Schumann) Pierre ex Beille [syn. Corynanthe yohimbi Schumann] [Fam. Rubiaceae] and its preparations. The bark contains alkaloids. The main alkaloid is yohimbine.

Chemistry and Pharmacology

Yohimbe contains up to 6% indole alkaloids, 1015% of which are yohimbine (quebrachine); also a-yohimbine (isoyohimbine), allo-yohimbine (dihydroyohimbine), yohimbinine, a-yohimbane, yohimbenine, corynantheine, and others (Betz et al., 1995; Budavari, 1996; Leung and Foster, 1996).

The Commission E did not report pharmacological actions.

Uses

The Commission E reported its unofficial use for sexual disorders, as an aphrodisiac, and for feebleness and exhaustion. The effectiveness of this herb and its preparations for the claimed applications is not sufficiently documented in the scientific literature, and thus the Commission E categorized it as an unapproved herb.

The Commission E did not find adequate documentation to support this use. The Evaluation section of the original monograph states, 'The therapeutic administration of yohimbe bark and its preparations is not recommended because of insufficient proof of efficacy and the unforeseeable correlation between risk and benefit.'

Contraindications

In existing liver and kidney diseases and in chronic inflammation of the sexual organs or prostate gland (McGuffin et al., 1997; Reynolds, 1989; Roth et al., 1984).

Side Effects

Therapeutic administration of yohimbine can cause nervous excitation, tremor, sleeplessness, anxiety, increased blood pressure, tachycardia, nausea, and vomiting. In case of existing liver and kidney diseases, yohimbe preparations should not be used. Interactions with psychopharmacological herbs have been reported.

Use During Pregnancy and Lactation

No data available.

Interactions with Other Drugs

May potentiate pharmaceutical MAO-inhibitors and, in high doses, potentiate hypotensive drugs (McGuffin et al., 1997).

Dosage and Administration

Evaluation: The therapeutic administration of yohimbe bark and its preparations is not recommended because of insufficient proof of efficacy and the unforeseeable correlation between risk and benefit (Commission E).

Yohimbine Hydrochloride: 5.4 mg, three times daily (Rice et al., 1996); 6 mg., three times daily (Morales et al., 1987; Reid et al., 1987; Reynolds, 1989; Werbach and Murray, 1994); 15-20 mg per day though higher doses up to 42 mg per day may be more effective (Werbach and Murray, 1994). Other sources state that yohimbine may be more effective at lower doses and that there are significant risks associated with doses over 10 mg (Devi, 1998; Reichert, 1997; Riley, 1994).

References

Betz, J.M., K.D. White, A. Der Marderosian. 1995. Gas chromatographic determination of yohimbine in commercial yohimbe products. J AOAC Int 78(5):11891194.

Bown, D. 1995. Encyclopedia of Herbs and Their Uses. New York: DK Publishing, Inc. 322.

Bruneton, J. 1995. Pharmacognosy, Phytochemistry, Medicinal Plants. Paris: Lavoisier Publishing.

Budavari, S. (ed.). 1996. The Merck Index: An Encyclopedia of Chemicals, Drugs, and Biologicals, 12th ed. Whitehouse Station, N.J.: Merck & Co, Inc.

De Smet, P.A. 1997. Yohimbe AlkaloidsGeneral Discussion. In: De Smet, P.A., K. Keller, Hnsel R., Chandler, R.F. (eds.) 1997. Adverse Effects of Herbal Drugs, Vol. 3. New York: Springer Verlag. 181205.

De Smet, P.A. and O.S. Smeets. 1994. Potential risks of health food products containing yohimbe extracts [letter]. BMJ 309(6959):958.

Devi, L. 1998. YohimbineClinical Study Shows Effects at Different Dose Levels. HerbClip 060481. Austin, TX: American Botanical Council.

Duke, J.A. 1997. The Green Pharmacy. Emmaus, PA: Rodale Press. 176, 188, 191192, 288.

Ernst, E. and M.H. Pittler. 1998. Yohimbine for erectile dysfunction: a systematic review and meta-analysis of randomized clinical trials. J Urol 159(2):433436.

Grasing, K. et al. 1996. Effects of yohimbine on autonomic measures are determined by individual values for area under the concentration-time curve. J Clin Pharmacol 36(9):814822.

Keay, R.W. 1989. Trees of Nigeria. Oxford: Clarendon Press.

Leung, A.Y. and S. Foster. 1996. Encyclopedia of Common Natural Ingredients Used in Food, Drugs, and Cosmetics, 2nd ed. New York: John Wiley & Sons, Inc.

McGuffin, M., C. Hobbs, R. Upton, A. Goldberg. 1997. American Herbal Product Association's Botanical Safety Handbook. Boca Raton: CRC Press.

Morales, A. et al. 1987. Is yohimbine effective in the treatment of organic impotence? Results of a controlled trial. J Urol 137(6):11681172.

Osol, A. and G.E. Farrar. 1955. The Dispensatory of the United States of America, 25th ed. Philadelphia, PA: J.B. Lippincott Company.

Owen, J.A. et al. 1987. The pharmacokinetics of yohimbine in man. Eur J Clin Pharmacol 32(6):577582.

Reichert, R. 1997. Yohimbine Pharmacokinetics. Quarterly Rev Nat Med Spring:1718.

Reid, K. et al. 1987. Double-blind trial of yohimbine in treatment of psychogenic impotence. Lancet 2(8556):421423.

Reynolds, J.E.F. (ed.). 1989. Martindale: The Extra Pharmacopoeia, 29th ed. London: The Pharmaceutical Press.

Rice, T.F. et al. 1996. Physicians' Desk Reference, 50th ed. Montvale, NJ: Medical Economics Company. 1283, 1322, 1363, 1892, 2552.

Riley, A.J. 1994. Yohimbine in the treatment of erectile disorder. Br J Clin Pract 48(3):133136.

Roth, L. et al. 1984. Giftpflanzen, Pflanzengifte. Munich: Ecomed.

Tyler, V.E. 1993. The Honest Herbal, 3rd ed. Binghamton, N.Y.: Pharmaceutical Products Press. 327329.

Werbach, M.R. and M.T. Murray. 1994. Botanical Influences on IllnessA Sourcebook of Clinical Research. Tarzana, CA: Third Line Press. 199202.

Additional Resources

Clark, J.T. 1991. Suppression of copulatory behavior in the male rats following central administration of clonidine. Neuropharmacology (U.K.) 30(4):373382.

Clark, J.T., E.R. Smith, J.M. Davidson. 1985. Testosterone is not required for the enhancement of sexual motivation by yohimbe. Physiological Behav 35(4):517521.

. 1985. Evidence for the modulation of sexual behavior by alpha-adrenoceptors in male rats. Neuroendocrinology (Switz) 41(1):3643.

Davis, G.A. and R. Kohl. 1977. The influence of alpha receptors on lordosis in the female rat. Pharm Biochem Behav 6(1):4753.

Smith, E.R. and J.M. Davidson. 1990. Yohimbine attenuates aging-induced sexual deficiencies in male rats. Physiol Behav 47(4):631634.

Smith, E.R., R.L. Lee, S.L. Schnur, J.M. Davidson. 1987. Alpha 2-adrenoceptor antagonists and male sexual behavior: 1. Mating Behavior. Physiol Behav 41(1):714.

. 1987. Alpha 2-adrenoceptor antagonists and male sexual behavior: 2. Erectile and ejaculatory reflexes. Physiol Behav 41(1):1519.

Taber, C.W. 1962. Taber's Cyclopedic Medical Dictionary, 9th ed. Philadelphia, PA: F.A. Davis Company. M59.

This material was adapted from The Complete German Commission E MonographsTherapeutic Guide to Herbal Medicines. M. Blumenthal, W.R. Busse, A. Goldberg, J. Gruenwald, T. Hall, C.W. Riggins, R.S. Rister (eds.) S. Klein and R.S. Rister (trans.). 1998. Austin: American Botanical Council; Boston: Integrative Medicine Communications.

1) The Overview section is new information.

2) Description, Chemistry and Pharmacology, Uses, Contraindications, Side Effects, Interactions with Other Drugs, and Dosage sections have been drawn from the original work. Additional information has been added in some or all of these sections, as noted with references.

3) The dosage for equivalent preparations (tea infusion, fluidextract, and tincture) have been provided based on the following example:

  • Unless otherwise prescribed: 2 g per day of [powdered, crushed, cut or whole] [plant part]
  • Infusion: 2 g in 150 ml of water
  • Fluidextract 1:1 (g/ml): 2 ml
  • Tincture 1:5 (g/ml): 10 ml

4) The References and Additional Resources sections are new sections. Additional Resources are not cited in the monograph but are included for research purposes.

This monograph, published by the Commission E in 1994, was modified based on new scientific research. It contains more extensive pharmacological and therapeutic information taken directly from the Commission E.

Excerpt from Herbal Medicine: Expanded Commission E Monographs
Copyright 2000 American Botanical Council
Published by Integrative Medicine Communications
Available from the American Botanical Council.