0071643192.pdf

TOXICOLOGY

■ Benzodiazepines for agitation and seizures

■ Sodium bicarbonate for QRS widening >100 msec

■ Antidote = cyproheptadine (serotonin antagonist).

■ Oral formulation only

■ Indicated for serotonin syndromein the patient able to take oral

medication

Monoamine Oxidase Inhibitors

Rarely used today as first-line agent for depression due to narrow therapeutic

window and drug interactions

Examples include:

■ Phenelzine (Nardil)

■ Tranylcypromaine (Parnate)

■ St. John’s Wort—an herbal preparation for depression thought to have

some monoamine oxidase inhibitor action

■ MAOB inhibitors (selegiline, rasagiline) are used to treat Parkinson disease

and are much less toxic in overdose.

MECHANISM/TOXICITY

■ Inhibition of monoamine oxidase →decreased inactivation of biogenic

amines, including epinephrine, norepinephrine, serotonin →excessive

circulating catecholamines.

■ Monamine oxidase may take weeks to regenerate after discontinuation of

MAOIs!

SYMPTOMS/EXAM

■ Characterized by excessive sympathetic activity

■ Symptoms are usually delayed 6–12 hoursfollowing overdose!

■ Agitation, mydriasis

■ Tachycardia, hyperthermia, hypertension

■ Muscle rigidity, hyperreflexia, myoclonus

■ Seizures, coma

■ Tyramine reaction—after ingestion of tyramine-containing foods (red

wine, cheese, etc.)

■ Headache, hypertension, diaphoresis, palpitations, and neuromuscular

excitation lasting for several hours

DIFFERENTIAL

■ Cocaine, amphetamines, PCP, ephedrine

DIAGNOSIS

■ Clinical diagnosis based on patient presentation.

■ MAOIs are usually not detected on standard toxicology screens.

TREATMENT

■ Supportive care

■ Aggressive treatment of hyperthermia

■ Activated charcoal, if early

■ Benzodiazepines for agitation, rigidity, seizures, tachycardia

Antidote to SSRIs, used in

mild-moderate serotonin

syndrome = cyproheptadine.

Symptom onset following

MAOI overdose is frequently

delayed 6–12 hours.

MAOI overdose symptoms are

those of life-threatening

excessive sympathetic activity.