Question: why maoi cause orthostatic hypotension?
Answer: Bretylium-like mechanism: A study by Gessa et al (1963) found that phenelzine and many other MAO inhibitors (e.g. iproniazid, pargyline, tranycypromine) have “bretylium-like” properties that prevent the release of norepinephrine from sympathetic nerve endings, a mechanism that could account for orthostatic hypotension.