Phenelzine pharmacokinetics

Pharmacokinetics Phenelzine and tranylcypromine are well absorbed orally. The clinical effects of phenelzine may continue for up to 2 weeks after discontinuation of therapy. When tranylcypromine is withdrawn, MAO activity is recovered in 3 to 5 days (possibly up to 10 days), although the drug is excreted in 24 hours. 

Only minimal information is available about the pharmacokinetics of the traditional MAOIs (e.g., phenelzine, tranylcypromine) ( 308). Such data are probably less critical for these versus other antidepressants, because MAOIs are consumed by their mechanism of action (i.e., irreversible inhibition of MAO by covalently binding to the enzyme). This mechanism accounts for the fact that traditional MAOIs have half-lives of only 2 to 4 hours, but their effects persist for an extended period because of their irreversible inactivation of their target. These MAOIs undergo presystemic or first pass degradation, and, thus, genetic or acquired alterations in this metabolism could alter their bioavailability and hence their effects. 

Table 21.15. Pharmacokinetics of the Monoamine Oxidase Inhibitors (MAOIs) Phenelzine Tranylcypromine Parameters (Nardil) (Parnate) Meclobemide ...

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