Basic Information
ID DDInter91 and DDInter2064
Interaction Monoamine oxidase inhibitors (MAOIs) may potentiate the hypotensive effect of some medications. MAOIs alone quite commonly produce orthostatic hypotension. This effect may stem from a gradual MAOI-induced accumulation of false neurotransmitters in peripheral adrenergic neurons that have minimal activity at alpha- and beta-adrenergic receptors, resulting in a functional block of sympathetic neurotransmission. The interaction has been reported with the concomitant use of beta-blockers.
Management Caution is advised during coadministration of MAOIs and other medications with hypotensive effects, especially during the first few weeks of treatment. Close monitoring for development of hypotension is recommended. Ambulatory patients should be advised to avoid rising abruptly from a sitting or recumbent position and to notify their physician if they experience dizziness, lightheadedness, syncope, orthostasis, or tachycardia.
References [1] Reggev A, Vollhardt BR "Bradycardia induced by an interaction between phenelzine and beta blockers." Psychosomatics 30 (1992): 106-8 [2] Pettinger WA, Soyangco FG, Oates JA "Inhibition of monoamine oxidase in man by furazolidone." Clin Pharmacol Ther 9 (1968): 442-7 [3] Schulz R, Antonin KH, Hoffmann E, et al. "Tyramine kinetics and pressor sensitivity during monoamine oxidase inhibition by selegiline." Clin Pharmacol Ther 46 (1989): 528-36 [4] Goldberg LI "Monoamine oxidase inhibitors: adverse reactions and possible mechanisms." JAMA 190 (1964): 456-62 [5] Ban TA "Drug interactions with psychoactive drugs." Dis Nerv Syst 36 (1975): 164-6 [6] "Product Information. Matulane (procarbazine)." Roche Laboratories (2001): [7] De Vita VT, Hahn MA, Oliverio VT "Monoamine oxidase inhibition by a new carcinostatic agent, n-isopropyl-a-(2-methylhydrazino)-p-toluamide (MIH). (30590)." Proc Soc Exp Biol Med 120 (1965): 561-5 [8] Kronig MH, Roose SP, Walsh BT, Woodring S, Glassman AH "Blood pressure effects of phenelzine." J Clin Psychopharmacol 3 (1983): 307-10 [9] Golwyn DH, Sevlie CP "Monoamine oxidase inhibitor hypertensive crisis headache and orthostatic hypotension." J Clin Psychopharmacol 13 (1993): 77-8 [10] "Product Information. Nardil (phenelzine)." Parke-Davis (2001): [11] "Product Information. Parnate (tranylcypromine)." SmithKline Beecham (2001): [12] "Product Information. Marplan (isocarboxazid)." Roche Laboratories (2001): [13] "Product Information. Xatral (alfuzosin)." Sanofi-Synthelabo Canada Inc (2002):
Alternative for Amrinone C01C
Angiotensin II Arbutamine
Alternative for Furazolidone G01A
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Potential Metabolism Interactions
Substrate-Substrate Interaction：If more than one drug is metabolized by the same CYP, it is possible that its metabolism is inhibited because of the competition between the drugs. That means, it can be useful to lower the dosage of the drugs in the drug-cocktail because they remain longer in the organism than in monotherapy.
Inhibitor-Inhibitor Interaction：Combining two or more inhibitors of one CYP, should be compensated by lowering the dosage of these drugs because the metabolism is reduced and the drugs remain longer in the organism than in monotherapy. Not adapting the dosage bears the risk of even more side effects.
Inhibitor-Substrate Interaction：Combining drugs that have inhibitory effect and are substrates of one particular CYP, should be compensated by lowering the dosage. They rest longer in the organism than in monotherapy. Not adapting the dosage bears the risk of even more side effects.