Pediatric emergency medicine trisk 3082 3082
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severe toxicity, even in the patient who takes them in appropriate doses. There are
three important clinical pictures of MAOI toxicity. First, because GI tract activity
of monoamine oxidase is inhibited, patients who take them appropriately and then
ingest foods that contain biogenic amines (e.g., tyramine in wines, cheeses, or soy
sauce) may develop severe hypertension with subsequent headache, seizures, or
stroke. The second picture of MAOI toxicity appears when those who take the
drug therapeutically are given certain sympathomimetic or serotonergic agents
causing the serotonin syndrome. Important examples of such drugs include
common agents in OTC cough and cold preparations (e.g., dextromethorphan),
analgesics (e.g., meperidine), and psychotropic medications (e.g., clomipramine,
fluoxetine, other SSRIs). This drug combination may quickly lead to
hyperpyrexia, skeletal muscle rigidity, cardiac arrhythmias, and death. Finally,
those with acute MAOI overdoses develop a clinical syndrome that includes
blood pressure instability, hyperpyrexia, skeletal muscle rigidity, opsoclonus,
seizures, and death.
Clinical Considerations. Because of the toxicity of these agents and the frequent
delay in their onset of activity (up to 24 hours), all patients with a history of
MAOI ingestion, regardless of symptoms, should be admitted to the hospital for
24 hours. Management of the patient with MAOI toxicity is largely dictated by
the specific toxic manifestations. In those with hypertensive reactions, treatment
consists of the immediate administration of an antihypertensive. The ideal agent
may be nitroprusside because its brief duration of action permits titration of
effect. In the treatment of hyperpyrexia, institute cooling measures promptly.
Because hyperpyrexia is often accompanied by skeletal muscle rigidity and
rhabdomyolysis, monitor serum creatine kinase levels and urine for
myoglobinuria. Benzodiazepines are often helpful in this situation and
neuromuscular blockade may be beneficial in patients with severe muscle rigidity
with hyperthermia. In the patient with acute overdose, treatment is directed to
hemodynamic stability. Because blood pressure changes occur quickly and
consist of hypotension and hypertension, hypertension should be treated with
short-acting agents and hypotension with fluid and vasopressor support. Intensive
care unit admission is mandatory for these patients because of their clinical
instability.
Phenothiazine Antipsychotics
CLINICAL PEARL
