Monoamine oxidase inhibitors
Monoamine oxidase inhibitors
MAOIs are divided into two classifications based on chemical structure:
- hydrazines, which include phenelzine sulfate
- nonhydrazines, consisting of a single drug, tranylcypromine sulfate.
Pharmacokinetics
MAOIs are absorbed rapidly and completely from the GI tract and are metabolized in the liver to inactive metabolites. These metabolites 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 serotonin available to the receptors, thereby relieving the symptoms of depression.
Pharmacotherapeutics
The indications for MAOIs are similar to those for other antidepressants. MAOIs are particularly effective for treating panic disorder with agoraphobia, eating disorders, posttraumatic stress disorder, 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 patient gains weight, sleeps more, and has a higher susceptibility to rejection.
Warning!Adverse reactions to MAOIs
Adverse reactions to mono-amine oxidase inhibitors (MAOIs) include:
- hypertensive crisis (when taken with tyramine-rich foods)
- orthostatic hypotension
- restlessness
- drowsiness
- dizziness
- headache
- insomnia
- constipation
- anorexia
- nausea and vomiting
- weakness
- joint pain
- dry mouth
- blurred vision
- peripheral edema
- urine retention
- transient impotence
- rash
- skin and mucous membrane hemorrhage.
Reaction relief
Adverse reactions may be avoided by giving the drug in small divided doses.
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It tackles typical depression, too
MAOIs may be used to treat typical depression resistant to other therapies or when other therapies are contraindicated. For example, tranylcypromine is the preferred MAOI for patients with depression who have liver disease. Other uses include treatment for:
- phobic anxieties
- neurodermatitis (an itchy skin disorder seen in anxious, nervous people)
- hypochondriasis (abnormal concern about health)
- refractory narcolepsy (sudden sleep attacks).
Moving from MAOIs
Monoamine oxidase inhibitors (MAOIs) should be discontinued 2 weeks before starting an alternative antidepressant. A 2-week waiting period (5 weeks for fluoxetine) should also elapse when discontinuing an antidepressant and starting an MAOI.
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 temperature, and coma.
Forbidden fruit (and other foods)
Certain foods can interact with MAOIs and produce severe reactions. The most serious reactions involve tyramine-rich foods, such as red wines, aged cheese, and fava beans. Foods with moderate tyramine contents’for example, yogurt and ripe bananas’may be eaten occasionally, but with care.
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