Yohimbe Bark for Impotence

Q. I bought an over-the-counter herbal supplement called yohimbe bark for impotence. Is it safe? Are there any side effects?

A. The herb yohimbe is the bark from the Pausinystalia yohimbe tree that grows in West Africa. It contains the alkaloid yohimbine, which is also available as a prescription medication. Yohimbine blocks receptors in the sympathetic nervous system and has been prescribed to treat impotence. It is also a monoamine oxidase inhibitor.