Management of Specific Poisons: CNS Agents (Anticonvulsants)

Comprehensive flashcards covering the management of CNS agents such as Barbiturates, Benzodiazepines, and miscellaneous sedative-hypnotics including toxic doses, mechanisms, and treatments.

Sedative

A substance that moderates activity and excitement while inducing a calming effect with minimum CNS depression.

Hypnotic

A substance that causes drowsiness and facilitates the onset and maintenance of natural sleep with more pronounced CNS depression.

Sedative-Hypnotic Barbiturates Mechanism of Action

These agents increase the duration of the GABA-gated chloride channel openings.

Barbiturates Mechanism of Toxicity

Generalized depression of neuronal activity through enhanced GABA-mediated synaptic inhibition and depression of cardiac contractility causing hypotension.

Fatal Dose of Phenobarbital

$$6-10\,g$$

Fatal Dose of Shorter-Acting Barbiturates

$$2-3\,g$$

Methohexital Fatal Exposure

IV injection of $1-3\,mg/kg$ has been reported to cause death in young women undergoing abortion.

Barbiturate Serum Level (Coma Threshold)

$60-80\,mg/L$ is usually associated with coma.

Phenobarbital Serum Level (Severe Hypotension)

$$150-200\,mg/L$$

Alkalinization of urine

A treatment method that increases the elimination of phenobarbital but not other barbiturates.

Benzodiazepines Mechanism of Action

Increase the frequency of the GABA-gated chloride channel openings and increase the affinity of GABA to its receptor.

Short-acting triazolobenzodiazepines

Includes Triazolam (Halcion), Alprazolam (Xanax), and Midazolam (Versed), which may cause respiratory arrest.

Flumazenil

A specific benzodiazepine receptor antagonist that rapidly reverses coma, administered IV starting at $0.1-0.2\,mg$ up to $3\,mg$.

Lorazepam (Ativan, Alzapam)

Currently the preferred drug for the initial management of Status epilepticus.

Chloral Hydrate Toxicity

Metabolized to trichloroethanol, which can sensitize the myocardium, resulting in cardiac arrhythmias.

Glutethimide Presentation

Often produces mydriasis, anticholinergic side effects, and prolonged, cyclic, or fluctuating coma.

Meprobamate Toxicity

A sedative-hypnotic agent where hypotension is more common than with other class members.

Methaqualone Presentation

Frequently causes unusual symptoms for sedative-hypnotics, including muscular hypertonicity, clonus, and hypereflexia.