The inhibition of tyramine oxidation and the tyramine hypertensive response ("cheese effect") may be independent phenomena.

Although the selective monoamine oxidase (MAO) inhibitor, (-)-deprenyl, substantially inhibits tyramine-oxidizing ability in the pig, intravenous tyramine challenge after pretreatment with this drug failed to produce the characteristic pressor response ("cheese effect") associated with other irreversible MAO inhibitors. Conversely, pretreatment with the tyramine oxidation-sparing selective MAO inhibitor, clorgyline, followed by intravenous tyramine, paradoxically resulted in a profound pressor response. We suggest that the action of standard MAO-inhibiting drugs may be compounded of two separate actions, usually associated but, in fact, unreleated.