<unk>  (), also known as quebrachine, is an indole alkaloid derived from the bark of the African tree Pausinystalia johimbe; also from the bark of the unrelated South American tree Aspidosperma quebracho-blanco.<unk>  is an α2-adrenergic receptor antagonist, and has been used in a variety of research projects. It is a veterinary drug used to reverse sedation in dogs and deer. While<unk>  behaves as an aphrodisiac in some mammals, it does not do so in humans. It has been prescribed as a treatment for erectile dysfunction, although its reported clinical benefits were modest and it has largely been superseded by the PDE5 inhibitor class of drugs. Substances that have purported to be extracts from the<unk> himbe tree have been marketed as dietary supplements for various purposes, but they contain highly variable amounts of<unk> , if any; no published scientific evidence supports their efficacy.
Yohimbine
Acebutolol
Phenylephrine
Metergoline
Amiloride
Cyclothiazide
Prazosin
Moclobemide