Title: Relationship between tyramine potentiation and monoamine oxidase (MAO) inhibition: comparison between moclobemide and other MAO inhibitors
Abstract: The pharmacodynamic properties of moclobemide, a reversible inhibitor of MAO‐A (RIMA), were compared with the properties of other reversible as well as older irreversible MAO inhibitors in human subjects. All the substances supposed to have MAO‐A‐inhibitory activity, with the exception of toloxatone, were shown by the decrease in plasma DHPG or MHPG levels to cause inhibition ranging between 50% and 85%. Toloxatone and low doses of deprenyl (a MAO‐B inhibitor) caused 20% and 17% inhibition respectively; higher doses of deprenyl, however, strongly inhibited MAO‐A. MAO‐B inhibition was confirmed for all nonselective and selective MAO‐B inhibitors. Moclobemide and clorgyli‐ne were found to be the most highly selective MAO‐A inhibitors, although both also inhibited 30% of platelet MAO‐B activity. Potentiation of the tyramine pressor effect is mainly influenced by the irreversibility and degree of MAO‐A inhibition. Tyramine sensitivity was raised (a factor of 10–30) by all irreversible MAO inhibitors in doses inhibiting MAO‐A; it diminished with increasing reversibility. In therapeutic doses, moclobemide potentiated the intravenous tyramine pressor effect 3 times less than the old irreversible MAO inhibitors; with the highest therapeutic dose, the tyramine sensitivity factor for moclobemide is only one‐seventh to one‐tenth that of tranylcypromine or phenelzine. Duration of action is obviously also closely related to the reversibility of inhibition: it ranged from up to 2 days with high doses of moclobemide to 3 weeks with tranylcypromine; clorgyline and phenelzine have been shown to maintain their action for several months. The new generation of RIMAs represents a significant progress in safety. Among the RIMAs having significant pharmacodynamic activity, moclobemide appears to be the safest, the most selective and the most readily reversible.
Publication Year: 1990
Publication Date: 1990-09-01
Language: en
Type: article
Indexed In: ['crossref', 'pubmed']
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Cited By Count: 27
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