0071643192.pdf

TOXICOLOGY

■ Activated charcoal

■ Multiple-dose activated charcoal: If large phenobarbital overdose

■ Whole-bowel irrigationif long-acting agents

■ Urinary alkalinization

■ For long-acting barbiturates (eg, phenobarbital) only

■ Noteffective for shorter-acting agents

■ To urine pH of 8.0

■ Hemodialysis for severely intoxicated patients refractory to above therapy

Benzodiazepines

Benzodiazepines are used as sedatives, to induce anesthesia, and to treat

epilepsy, including status epilepticus.

They are categorized by their duration of action.

■ Short-acting (eg, midazolam)

■ Intermediate-acting (eg, lorazepam)

■ Long-acting (eg, diazepam)

The shorter-acting agents are more lipophilic, and therefore cross the blood-

brain barrier more rapidly (rapid on, rapid off). Half-life is nota good indica-

tor of duration of effect.

Severe toxicity from benzodiazepine exposure is rare unless combined with

other agents that have synergistic effects.

MECHANISM/TOXICITY

■ Enhanced binding of GABA to GABA-A channels →depression of neu-

ronal firing.

■ Peripheral vasodilatation

SYMPTOMS/EXAM

■ Mild to moderate intoxication: Lethargy, slurred speech, ataxia

■ Severe intoxication: Coma, respiratory depression, hypotension

DIAGNOSIS

■ Usually based on history of exposure.

■ Many urine toxicology tests screen for benzodiazepines.

TREATMENT

■ Supportive therapy

■ Activated charcoal (if <1 hour and no significant CNS depression)

■ Antidote: Flumazenil

■ Benzodiazepine receptor antagonist

■ Duration of effect = 1 hour (recurrent sedation possible)

■ Limited utility in the ED (mostly for reversal of procedural sedation)

■ Contraindications:

■ Chronic benzodiazepine use (may induce withdrawal)

■ Coingestion of seizure-inducing medication (eg, TCAs)

■ Suspected increased ICP

Urinary alkalinization is

effective for long-acting

barbiturates (phenobarbital)

only.

Flumazenil contraindications:

Chronic benzodiazepine use

Coingestion of seizure-

inducing meds

Suspected↑ICP