Monoamine oxidase inhibitors

Monoamine oxidase inhibitors

MAOIs are divided into two classifications based on chemicalstructure:

§    hydrazines, which include phenelzine sulfate

§    nonhydrazines, consisting of a single drug, tranylcypromine sul-fate.

Pharmacokinetics

MAOIs are absorbed rapidly and completely from the GI tract and are metabolized in the liver to inactive metabolites. These metabo-lites are excreted mainly by the GI tract and, to a lesser degree, by the kidneys.

Pharmacodynamics

MAOIs appear to work by inhibiting MAO, an enzyme that’s widely distributed throughout the body and that normally metabolizes many neurotransmitters, including norepinephrine, dopamine, and serotonin. This leaves more norepinephrine, dopamine, and sero-tonin available to the receptors, thereby relieving the symptoms of depression.

Pharmacotherapeutics

The indications for MAOIs are similar to those for other antide-pressants. MAOIs are particularly effective for treating panic dis-order with agoraphobia, eating disorders, posttraumatic stress dis-order, and pain disorders.

MAOIs may be more effective than other antidepressants in the treatment of atypical depression. Atypical depression produces signs opposite to those of typical depression. For example, the pa-tient gains weight, sleeps more, and has a higher susceptibility to rejection.

It tackles typical depression, too

MAOIs may be used to treat typical depression resistant to other therapies or when other therapies are contraindicated. For exam-ple, tranylcypromine is the preferred MAOI for patients with de-pression who have liver disease. Other uses include treatment for:

·                 phobic anxieties

·                 neurodermatitis (an itchy skin disorder seen in anxious, ner-vous people)

·                 hypochondriasis (abnormal concern about health)

·                 refractory narcolepsy (sudden sleep attacks).

Drug interactions

MAOIs interact with a wide variety of drugs:

·                  Taking MAOIs with amphetamines, methylphenidate, levodopa, sympathomimetics, and nonamphetamine appetite suppressants may increase catecholamine release, causing hypertensive crisis.

·                 Using them with fluoxetine, TCAs, citalopram, clomipramine, trazodone, sertraline, paroxetine, and fluvoxamine may result in an elevated body temperature, excitation, and seizures.

·                 When taken with doxapram, MAOIs may cause hypertension and arrhythmias and may increase the adverse reactions to doxapram.

·                 MAOIs may enhance the hypoglycemic effects of antidiabetic drugs.

·                 Administering MAOIs with meperidine may result in excitation, hypertension or hypotension, extremely elevated body tempera-ture, and coma. (See Moving from MAOIs.)

Forbidden fruit (and other foods)

Certain foods can interact with MAOIs and produce severe reac-tions. The most serious reactions involve tyramine-rich foods, such as red wines, aged cheese, and fava beans. Foods with mod-erate tyramine contents—for example, yogurt and ripe bananas— may be eaten occasionally, but with care. (See Adverse reactionsto MAOIs.)