Herb/Sympatholytic/Impotence Agent
PREGNANCY RECOMMENDATION: No Human Data—No Relevant Animal Data
BREASTFEEDING RECOMMENDATION: No Human Data—Probably Compatible
PREGNANCY SUMMARY
No reports describing the use of yohimbine or yohimbe in human pregnancy have been located. The one animal reproduction study located was not relevant for the reasons cited. Yohimbe is available over the counter as a herbal supplement and has been used as an aphrodisiac and for weight loss and sexual dysfunction. Although it has no FDA-sanctioned indications, yohimbine is available by prescription for male erectile dysfunction. It has also been used for treatment of orthostatic hypotension.
FETAL RISK SUMMARY
Yohimbine is an extract of the bark of the Pausinystalia yohimbe tree and chemically related to reserpine. The term “yohimbe” refers to the bark extract, which is available in many health stores as a supplement, while “yohimbine” refers to the pharmaceutical pure extract. Both yohimbine and yohimbe are administered orally. Yohimbine is available only by prescription. Yohimbine and yohimbe have been used as aphrodisiacs, for weight loss, and for sexual dysfunction. The primary off-label indication for yohimbine is sexual dysfunction, particularly for the treatment of male erectile dysfunction. This action may be secondary to its blockage of α2-adrenergic receptors. A second off-label indication is for orthostatic hypotension. Yohimbine is metabolized to apparently inactive metabolites. Plasma protein binding is 82% and the elimination half-life is about 36 minutes (1,2).
In a reproduction study with rats, a single IM injection (20 mg/kg) of yohimbine on day 5 of gestation did not alter the course of pregnancy or affect litter size (3). However, the dose was given before the period of organogenesis (days 9–17 in rats) and thus missed the period of greatest vulnerability for structural anomalies. Moreover, the dose was not compared with the human dose based on BSA or AUC, so the results are not interpretable for estimating human risk.
No studies on the carcinogenicity, mutagenicity, or effects on fertility of yohimbine have been located. In male Swiss albino mice, oral doses of yohimbe for 90 days resulted in significant increases in sperm abnormalities and the weight of seminal vesicles, and a decrease in sperm motility and count. A nonsignificant decrease in pre- and postimplants also was observed (4).
It is not known if yohimbine crosses the human placenta. The molecular weight (about 355) suggests that exposure of the embryo–fetus will occur. However, the very short elimination half-life should limit the amount crossing the placenta.
BREASTFEEDING SUMMARY
No reports describing the use of yohimbine or yohimbe during human lactation have been located. In rats, the sympatholytic (blockage of presynaptic α2-adrenergic receptors) action of the herb was shown to increase prolactin levels (5). This effect has not been studied in humans. Nevertheless, the relatively low molecular weight (about 355) suggests that the herb will be excreted into breast milk. Moreover, both formulations of the herb are basic and accumulation in breast milk may occur. The effect of this exposure on a nursing infant is unknown.
References
1.DerMarderosian A, Beutler JA, eds. Yohimbe. The Review of Natural Products. St. Louis, MO: Wolters Kluwer Health, 2009.
2.Tam SW, Worcel M, Wyllie M. Yohimbine: a clinical review. Pharmacol Ther 2001;91:215–43.
3.Bovet-Nitti F, Bovet D. Action of some sympatholytic agents on pregnancy in the rat. Proc Soc Exp Biol Med 1959;100:555–7.
4.Al-Majed AA, Al-Yahya AA, Al-Bekairi AM, Al-Shabanah OA, Qureshi S. Reproductive, cytological and biochemical toxicity of yohimbe in male Swiss albino mice. Asian J Androl 2006;8:469–76.
5.Lien EL, Morrison A, Kassarich J, Sullivan D. Alpha-2-adrenergic control of prolactin. Neuroendocrinology 1986;44:184–9.