Yohimbine is an indolealkylamine alkoloid with chemical similarity to reserpine. Yohimbine has been isolated from Cornanthe johimbe, Rubiaceae and related trees, as well as Rauwolfia serpentina. Both yohimbine and a diastereoisomer, corynanthine, are α2-adrenoceptor antagonists of limited duration. Yohimbine has limited effect on smooth muscle, but it readily passes through the blood-brain barrier and produces a complex pattern of responses at doses lower than required to produce a-adrenergic blockade. Yohimbine has been reported to produce central excitation (e.g., elevated blood pressure, increased heart rate, increased motor activity, tremor, irritability, vomiting, nausea and sweating) and to act as an antidiuretec (through its ability to release antidiuretic hormone). Some evidence also suggests that yohimbine can act as an aphrodisiac,3 although this effect may be limited to individuals with vascular diseases.