Classifications: psychotherapeutic; antidepressant; monoamine oxidase (mao) inhibitor;
Therapeutic: antidepressant; mao inhibitor

Pregnancy Category: C


15 mg tablets


Potent hydrazine (monoamine oxidase) MAO inhibitor. Antidepressant and diverse effects believed to be due to irreversible inhibition of MAO, thereby permitting increased concentrations of endogenous epinephrine, norepinephrine, serotonin, and dopamine within presynaptic neurons and at receptor sites. Also thought to inhibit hepatic microsomal drug-metabolizing enzymes; thus it may intensify and prolong the effects of many drugs.

Therapeutic Effect

Antidepressant utilization of the drug is limited to individuals who do not respond well to other classes of antidepressants. Termination of drug action depends on regeneration of MAO inhibitors, which occurs 2–3 wk after discontinuation of therapy.


Management of endogenous depression, depressive phase of manic-depressive psychosis, and severe exogenous (reactive) depression not responsive to more commonly used therapy.


Hypersensitivity to MAO inhibitors; suicidal ideation; pheochromocytoma; hyperthyroidism; CHF, acute MI, cardiac arrhythmias, hypertension, history of angina pectoris; cardiovascular or cerebrovascular disease; increased intracranial pressure; intracranial bleeding; renal failure; impaired kidney function, hypernatremia; atonic colitis; glaucoma; history of frequent or severe headaches; history of liver disease, abnormal liver function tests; alcoholism, alcohol intoxication; depression, accompanying alcoholism or drug addiction; older adult or debilitated patients; paranoid schizophrenia; pregnancy (category C), lactation. Safety in children <6 y of age is not established.

Cautious Use

Epilepsy; pyloric stenosis; diabetes; manic-depressive states; agitated patients; schizophrenia or psychosis; seizures; suicidal tendencies; chronic brain syndromes.

Route & Dosage

Adult: PO 15 mg t.i.d., rapidly increase to at least 60 mg/d, may need up to 90 mg/d


  • Discontinue at least 10 d before elective surgery to allow time for recovery from MAO before anesthetics are given.
  • Avoid rapid withdrawal of MAO inhibitors, particularly after high dosage, since a rebound effect may occur (e.g., headache, excitability, hallucinations, and possibly depression).
  • Store in tightly covered containers away from heat and light.

Adverse Effects (≥1%)

Body as a Whole: Dizziness or vertigo, headache, orthostatic hypotension, drowsiness or insomnia, weakness, fatigue, edema, tremors, twitching, akathisia, ataxia, hyperreflexia, faintness, hyperactivity, marked agitation, anxiety, seizures, trismus, opisthotonos, respiratory depression, coma. CNS: Mania, hypomania, confusion, memory impairment, delirium, hallucinations, euphoria, acute anxiety reaction, toxic precipitation of schizophrenia, convulsions, peripheral neuropathy. CV: Hypertensive crisis (intense occipital headache, palpitation, marked hypertension, stiff neck, nausea, vomiting, sweating, fever, photophobia, dilated pupils, bradycardia or tachycardia, constricting chest pain, intracranial bleeding), hypotension or hypertension, circulatory collapse. GI: Constipation, dry mouth, nausea, vomiting, anorexia, weight gain. Hematologic: Normocytic and normochromic anemia, leukopenia. Skin: Hyperhidrosis, skin rash, photosensitivity. Special Senses: Blurred vision.

Diagnostic Test Interference

Phenelzine may cause a slight false increase in serum bilirubin.


Drug: tricyclic antidepressants may cause hyperpyrexia, seizures; fluoxetine, sertraline, paroxetine may cause serotonin syndrome (see Appendix F); sympathomimetic agents (e.g., amphetamine, phenylephrine, phenylpropanolamine), guanethidine and reserpine may cause hypertensive crisis; cns depressants have additive CNS depressive effects; opiate analgesics (especially meperidine) may cause hypertensive crisis and circulatory collapse; buspirone, hypertension; general anesthetics, prolonged hypotensive and CNS depressant effects; hypertension, headache, hyperexcitability reported with dopamine, methyldopa, levodopa, tryptophan; metrizamide may increase risk of seizures; hypotensive agents and diuretics have additive hypotensive effects. Food: Aged meats or aged cheeses, protein extracts, sour cream, alcohol, anchovies, liver, sausages, overripe figs, bananas, avocados, chocolate, soy sauce, bean curd, natural yogurt, fava beans—tyramine-containing foods—may precipitate hypertensive crisis. Avoid chocolate or caffeine. Herbal: Ginseng, ephedra, ma huang, St. John's wort may cause hypertensive crisis.


Absorption: Readily absorbed from GI tract. Onset: 2 wk. Metabolism: Rapidly metabolized. Elimination: 79% of metabolites excreted in urine in 96 h.

Nursing Implications

Assessment & Drug Effects

  • Evaluate patient's BP in standing and recumbent positions. Prior to initiation of treatment.
  • Monitor children, adolescents, and adults for changes in behavior that may indicate suicidality.
  • Lab tests: Perform baseline CBC and liver function tests. Also perform periodic CBC and liver function tests during prolonged or high-dose therapy.
  • Monitor BP and pulse between doses when titrating initial dosages. Observe closely for evidence of adverse drug effects. Thereafter, monitor at regular intervals throughout therapy.
  • Report immediately if hypomania (exaggeration of motility, feelings, and ideas) occurs as depression improves. This reaction may also appear at higher than recommended doses or with long-term therapy.
  • Observe for and report therapeutic effectiveness of drug: Improvement in sleep pattern, appetite, physical activity, interest in self and surroundings, as well as lessening of anxiety and bodily complaints.
  • Observe patient with diabetes closely for S&S of hypoglycemia (see Appendix F). Patients on prolonged therapy should be checked periodically for altered color perception, changes in fundi or visual fields. Changes in red-green vision may be the first indication of eye damage.

Patient & Family Education

  • Drug is usually discontinued if no therapeutic response occurs after 3 or 4 wk. Maximum antidepressant effects generally appear in 2–6 wk and persist several weeks after drug withdrawal.
  • Avoid self-medication. OTC preparations containing dextromethorphan, sympathomimetic agents, or antihistamines (e.g., cough, cold, and hay fever remedies, appetite suppressants) can precipitate severe hypertensive reactions if taken during therapy or within 2–3 wk after discontinuation of an MAO inhibitor.
  • Report immediately to physician the onset of headache and palpitation, prodromal symptoms of hypertensive crisis or any other unusual effects which may indicate need to discontinue therapy.
  • Do not consume foods and beverages containing tyramine or tryptophan or drugs containing pressor agent. These can cause severe hypertensive reactions. Get a list from your care provider.
  • Avoid drinking excessive caffeine and chocolate beverages (e.g., coffee, tea, cocoa, or cola).
  • Discuss with physician wearing elastic stockings and elevating legs when sitting to minimize hypotensive effects of drug.
  • Make position changes slowly, especially from recumbent to upright posture, and dangle legs over bed a few minutes before rising to walk. Avoid standing still for prolonged periods. Also avoid hot showers and baths (resulting vasodilatation may potentiate hypotension); lie down immediately if feeling light-headed or faint.
  • Check weight 2 or 3 times per wk and report unusual gain.
  • Report jaundice. Hepatotoxicity is believed to be a hypersensitivity reaction unrelated to dosage or duration of therapy.
  • Avoid overexertion while taking this drug. MAO inhibitors may suppress anginal pain that would otherwise serve as a warning sign of myocardial ischemia.

Common adverse effects in italic, life-threatening effects underlined; generic names in bold; classifications in SMALL CAPS; Canadian drug name; Prototype drug

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