Medication Summary
Pharmacologic therapy in patients with monoamine oxidase inhibitor (MAOI) toxicity is principally directed toward decontamination and reversal of the cardiac and central nervous system (CNS) effects of these drugs. Pharmaceutical agents should be used after the patient is adequately hydrated. Choose medications that have a short half-life and are easily titratable because of the rapid changes in cardiovascular status that may occur from a drug-food interaction, drug-drug interaction, or overdose involving an MAOI.
GI decontaminants
Class Summary
Useful for limiting systemic burden of the ingested substance, especially if administered within 1-4 h of ingestion.
Activated charcoal (Liqui-Char)
Emergency treatment in poisoning caused by drugs and chemicals. Network of pores present in activated charcoal adsorbs 100-1000 mg of drug per gram of charcoal. Does not dissolve in water.
For maximum effect, administer within 30 min of ingesting poison.
Alternate use of cathartic and monitor for active bowel sounds.
Cardiovascular agents
Class Summary
Used to lower blood pressure during hypertensive crisis.
Nitroprusside (Nitropress)
Produces vasodilation and increases inotropic activity of the heart. At higher doses, may exacerbate myocardial ischemia by increasing the heart rate.
Nitroglycerin IV (Deponit, Nitrostat)
Relaxes vascular smooth muscle by stimulating intracellular cyclic guanosine monophosphate production, resulting in a decreased blood pressure.
May administer bolus of 12.5-25 mcg before continuous infusion.
Initial infusion rate of 10-20 mcg/min may be increased 5-10 mcg/min, q5-10 min until desired clinical or hemodynamic response is achieved.
Infusion rates of 500 mcg/min have occasionally been required.
Benzodiazepines
Class Summary
Useful to control agitation and for treatment of drug-induced seizures.
Diazepam (Valium)
Depresses all levels of CNS (eg, limbic and reticular formation), possibly by increasing activity of GABA.
Lorazepam (Ativan)
Sedative hypnotic with short onset of effects and relatively long half-life.
By increasing the action of GABA, a major inhibitory neurotransmitter in the brain, may depress all levels of CNS, including limbic and reticular formation.
Midazolam (Versed)
Used as alternative in termination of refractory status epilepticus. Because water soluble, takes approximately 3 times longer than diazepam to peak EEG effects. Thus, clinician must wait 2-3 min to fully evaluate sedative effects before initiating procedure or repeating dose. Has twice the affinity for benzodiazepine receptors than diazepam. May be administered IM if unable to obtain vascular access.
Antidotes
Class Summary
Used as a third-line treatment for MAOI-induced serotonin toxicity after the interventions listed above. [3]
Cyproheptadine
Cyproheptadine is a first-generation antihistamine with antiserotonergic and anticholinergic properities. Its effectiveness in patients with a serotonergic crisis due to MAOI-toxicity has not been proven, but could be useful as an adjunctive treatment to hydration and benzodiazepines. It is dosed at 12 mg orally with 2 mg orally every two hours as needed for symptomatic control.
