Monoamine Oxidase Inhibitor Overdose

Potential food or drug interactions can occur during therapeutic use

Ingestion of tyramine-containing foods (eg, aged cheese and red wines) or any sympathomimetic drug may cause a severe hypertensive reaction

Severe or fatal hyperthermia (serotonin syndrome)

• May occur when monoamine oxidase inhibitors (MAOIs) are given with serotonin-enhancing drugs (eg, meperidine, fluoxetine, paroxetine, fluvoxamine, venlafaxine, tryptophan, dextromethorphan, tramadol)

• Can also occur with moclobemide (an MAOI not available in the United States) and linezolid, which has MAOI properties

• Can also occur with selective serotonin reuptake inhibitors (SSRIs) in large doses or in combination with other SSRIs, even in the absence of an MAOI or meperidine

Acute overdose

• Ataxia, excitement, hypertension, and tachycardia

• Several hours later: hypotension, convulsions, and hyperthermia

Food or drug hypertensive reaction

• Hypertension

• Tachycardia

• Headache

• Possible intracranial hemorrhage

Serotonin syndrome

• Fever

• Agitation

• Delirium

• Diaphoresis

• Hyperreflexia

• Clonus (spontaneous, inducible, ocular)

• Hyperthermia (can be life-threatening)

Serum drug levels are not available nor useful

Generally not detected on urine toxicology screens

Acute overdose

• Administer activated charcoal, 60–100 g orally or via gastric tube, mixed in aqueous slurry if ingestion is within 1

• Treat hypotension with fluids and positioning, but avoid use of pressor agents if possible

• Treat severe hypertension with nitroprusside, phentolamine, or other rapid-acting vasodilators

Serotonin syndrome

• Cyproheptadine, 4 mg orally (or by gastric tube) every hour for three or four doses, or chlorpromazine 25 mg intravenously, can be effective

Observe patients for at least 24 h because hyperthermia may be delayed (see Hyperthermia)