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Toxicity, Monoamine Oxidase Inhibitor: Treatment & Medication
Updated: Jan 23, 2008
- Overview
- Differential Diagnoses & Workup
- Treatment & Medication
- Follow-up
Treatment
Medical Care
As with most toxic ingestions, the cornerstone of management is continuous monitoring, decontamination when clinically indicated, and meticulous supportive care.
- Give careful attention to airway management.
- Maintain euvolemia because patients with monoamine oxidase inhibitor (MAOI) poisoning can become dehydrated secondary to their hypermetabolic state.
- Maintain euthermia, especially in patients with suspected serotonin syndrome. Water mist sprays with fanning are effective. The removal of clothing and the use of cooling blankets may also be effective.
- Treat seizures and agitation with intravenous benzodiazepines.
- Decontamination with activated charcoal should be performed with caution and with attention to the possibility of airway compromise.
- Treat hypertension only if it is sustained and clinically significant.
Consultations
- Close consultation with a medical toxicologist or personnel from a regional poison center is recommended.
- Consult a pediatric intensivist.
- Consult a psychiatrist in cases of suspected intentional ingestion.
Medication
Decontamination agents
Consider activated charcoal decontamination in any patient who presents within one hour of the ingestion. Activated charcoal is used for drug adsorption and may be sufficient in mild-to-moderate toxicity. It is not absorbed and is excreted entirely through the GI tract.
Activated charcoal (Actidose-Aqua, Liqui-Char)
Emergency treatment in drug or chemical poisoning. Network of pores adsorbs 100-1000 mg of drug per gram of charcoal, decreasing GI absorption of the poison. Does not dissolve in water. In an acute overdose, most effective if given within 1 h of ingestion.
Adult
50-100 g PO (1 g/kg) or 10 times amount of ingested poison; administer as susp in 4-8 oz of water
Pediatric
1 g/kg PO administered with water as a slurry
May inactivate ipecac syrup if used concomitantly; decreases effectiveness of coadministered medications; do not mix with sherbet, milk, or ice cream (decreases adsorptive properties)
Documented hypersensitivity; poisoning or mineral acid or alkali overdose
Pregnancy
C - Fetal risk revealed in studies in animals but not established or not studied in humans; may use if benefits outweigh risk to fetus
Precautions
Not effective in ethanol, methanol, or iron salt poisoning; monitor airway reflexes, neurologic parameters, and bowel sounds
Vasopressors
Sympathomimetics produce direct or indirect stimulation of adrenergic receptors and have various actions depending on the specific receptors involved. Stimulation of alpha1-receptors produces smooth muscle contraction. In the cardiovascular system, this effect leads to vasoconstriction and increased blood pressure; in the eye, this effect leads to mydriasis. Other affected organs include the urinary sphincter and uterus. Stimulation of beta1-receptors has an inotropic effect and also increases the heart rate. Stimulation of beta2-receptors leads to smooth muscle relaxation and produces vasodilatation.
Hypotension is initially treated with isotonic fluids. Vasoactive agents are used if hypotension remains refractory despite the administration of intravenous fluids. Norepinephrine is preferred to dopamine because dopamine is an indirect sympathomimetic and can cause an uncontrollable and erratic release of norepinephrine.
Norepinephrine (Levophed)
Used to treat protracted hypotension after adequate fluid-volume replacement. Stimulates beta1- and alpha-adrenergic receptors, which in turn increase cardiac muscle contractility, heart rate, and vasoconstriction. As a result, systemic blood pressure and coronary blood-flow increase.
Adult
0.5-30 mcg/min IV infusion; titrate to effect
Pediatric
0.05-1 mcg/kg/min IV infusion; titrate to effect
In MAOI poisoning, effects can be potentiated; start at low doses; effects increase with concurrent tricyclic antidepressants, MAOIs, antihistamines, guanethidine, methyldopa, or ergot alkaloids; atropine may block reflex tachycardia caused by norepinephrine and enhances pressor response
Documented hypersensitivity; peripheral or mesenteric vascular thrombosis because ischemia may be increased and area of infarct extended
Pregnancy
D - Fetal risk shown in humans; use only if benefits outweigh risk to fetus
Precautions
If possible, correct blood-volume depletion before administration; administer into large vein because extravasation can cause severe tissue necrosis; caution in occlusive vascular disease
Antihypertensives
Do not use these drugs routinely. Often, the hypertension is transient and clinically insignificant. Avoid administering pure beta-blockers because they can produce an unopposed alpha effect.
Sodium nitroprusside (Nitropress)
Allows control of hypertensive emergency with rapid onset and short duration. Used as continuous infusion in closely monitored setting (ie, arterial access in pediatric ICU). Produces vasodilation and increases inotropic activity of the heart. At higher doses. May exacerbate myocardial ischemia by increasing heart rate.
Adult
0.1-8 mcg/kg/min IV infusion; titrate to effect
Pediatric
Administer as in adults
Effects additive when administered with other hypotensive agents
Documented hypersensitivity; idiopathic hypertrophic subaortic stenosis and atrial fibrillation or flutter
Pregnancy
C - Fetal risk revealed in studies in animals but not established or not studied in humans; may use if benefits outweigh risk to fetus
Precautions
Use only after euvolemia established; caution in increased intracranial pressure, hepatic failure, severe renal impairment, or hypothyroidism; caution in cerebrovascular disease or coronary artery disease; in renal or hepatic insufficiency, levels may increase and can cause cyanide toxicity; can lower blood pressure and thus should be used only if mean arterial pressure >70 mm Hg
Labetalol (Normodyne, Trandate)
Blocks beta1-, alpha-, and beta2-adrenergic receptor sites, decreasing blood pressure.
Adult
20-30 mg IV over 2 min, followed by 40-80 mg q10min; alternately, start continuous infusion at 2 mg/min until blood pressure controlled; not to exceed 300 mg/dose
Pediatric
0.2-0.5 mg/kg/dose IV; not to exceed 20 mg/dose or continuous infusion of 0.25-1.5 mg/kg/h
Decreases effect of diuretics and increases toxicity of methotrexate, lithium, and salicylates; cimetidine may increase blood levels; glutethimide may decrease effects by inducing microsomal enzymes
Documented hypersensitivity; cardiogenic shock, pulmonary edema, bradycardia, atrioventricular block, uncompensated congestive heart failure, reactive airway disease, and severe bradycardia
Pregnancy
C - Fetal risk revealed in studies in animals but not established or not studied in humans; may use if benefits outweigh risk to fetus
Precautions
Caution in impaired hepatic function; discontinue if signs of liver dysfunction present
Phentolamine (Regitine)
Alpha1- and alpha2-adrenergic blocker that blocks circulating epinephrine and norepinephrine action, reducing hypertension that results from catecholamine effects on the alpha-receptors.
Adult
1-5 mg IV bolus, repeat q10-15min prn
Pediatric
0.02-0.1 mg/kg IV bolus, may repeat q10-15min prn; not to exceed 5 mg/dose
Concurrent epinephrine or ephedrine may decrease effects; ethanol increases toxicity
Documented hypersensitivity; coronary or cerebral arteriosclerosis and renal impairment
Pregnancy
C - Fetal risk revealed in studies in animals but not established or not studied in humans; may use if benefits outweigh risk to fetus
Precautions
Caution in tachycardia, peptic ulcer, and gastritis; cerebrovascular occlusions and myocardial infarctions can occur
Anticonvulsants
These agents are used to prevent seizures and terminate clinical and electrical seizure activity.
Lorazepam (Ativan)
Benzodiazepines can be used to treat agitation, seizures, or muscle rigidity.
Adult
2 mg IV, slowly over 2 min
Pediatric
0.1 mg/kg IV; not to exceed 2 mg/dose; may be repeated
Probenecid and valproic acid increase concentration (may need to reduce dose); theophylline can reverse sedative effects
Documented hypersensitivity
Pregnancy
D - Fetal risk shown in humans; use only if benefits outweigh risk to fetus
Precautions
May need to adjust dose in hepatic and renal insufficiency
More on Toxicity, Monoamine Oxidase Inhibitor |
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| Differential Diagnoses & Workup: Toxicity, Monoamine Oxidase Inhibitor |
 Treatment & Medication: Toxicity, Monoamine Oxidase Inhibitor |
| Follow-up: Toxicity, Monoamine Oxidase Inhibitor |
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References
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Further Reading
Keywords
monoamine oxidase inhibitor, antidepressant overdose, antidepressant poisoning, antidepressant overdoses, antidepressant poisonings, antidepressant-induced hepatotoxicity, childhood ingestions, MAO antidepressant, MAO antidepressant overdose, MAO antidepressant toxicity, MAO antidepressant poisoning, MAOI, MAOIs, MAOI overdose, MAOI toxicity, MAOI poisoning, monoamine oxidase A, MAO-A, monoamine oxidase B, MAO-B, phenelzine, tranylcypromine, isocarboxazid, Parkinson disease, methicillin-resistant Staphylococcus aureus, hypertension, tachycardia, hyperpexia, mydriasis, diaphoresis, rhabdomyolysis, renal failure, pulmonary edema, myocardial infarction, disseminated intravascular coagulopathy, serotonin syndrome
