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  1. Pharmacology. Pentobarbital is a short-acting barbiturate with anticonvulsant as well as sedative-hypnotic properties. It is used as a third-line drug in the treatment of status epilepticus. It also may reduce intracranial pressure in patients with cerebral edema by inducing vasoconstriction. After intravenous administration of a single dose, the onset of effect occurs within about 1 minute and lasts about 15 minutes. After intramuscular administration, the onset of effect is slower (10–15 minutes). Pentobarbital demonstrates a biphasic elimination pattern; the half-life of the initial phase is 4 hours, and the terminal phase half-life is 35–50 hours. Effects are prolonged after termination of a continuous infusion.

  2. Indications

    1. Pentobarbital is used for the management of status epilepticus that is unresponsive to conventional anticonvulsant therapy (eg, diazepam, phenytoin, or phenobarbital). If the use of pentobarbital for seizure control is considered, consultation with a neurologist is recommended.

    2. Pentobarbital is used to manage elevated intracranial pressure in conjunction with other agents.

    3. It may be used therapeutically or diagnostically for patients with suspected alcohol or sedative-hypnotic drug withdrawal syndrome.

    4. It has been used to manage stimulant-induced agitation and sympathomimetic symptoms refractory to benzodiazepines.

  3. Contraindications

    1. Known sensitivity to the drug.

    2. Manifest or latent porphyria.

  4. Adverse effects

    1. Central nervous system depression, coma, and respiratory arrest may occur, especially with rapid bolus or excessive doses.

    2. Hypotension may result, especially with rapid intravenous infusion (>50 mg/min). This may be caused by the drug itself or the propylene glycol diluent.

    3. Laryngospasm and bronchospasm have been reported after rapid intravenous injection, although the mechanism is unknown.

    4. Parenteral solutions are highly alkaline, and precautions need to be taken to avoid extravasation. Intra-arterial infusions may cause vasospasms and gangrene. Subcutaneous administration may cause necrosis and is not recommended.

    5. Use in pregnancy. FDA Category D (possible fetal risk). Pentobarbital readily crosses the placenta, and chronic use may cause hemorrhagic disease of the newborn (owing to vitamin K deficiency) or neonatal dependency and withdrawal syndrome. However, these potential effects do not preclude its acute, short-term use in a seriously symptomatic patient (See Phenytoin and Fosphenytoin).

  5. Drug or laboratory interactions

    1. Pentobarbital has additive CNS and respiratory depression effects with other barbiturates as well as with sedative and opioid drugs.

    2. Hepatic enzyme induction generally is not encountered with acute pentobarbital overdose, although it may occur within 24 to 48 hours.

    3. Clearance may be enhanced by hemoperfusion, so that supplemental doses are required during the procedure.

  6. Dosage and method of administration

    1. Intermittent intravenous bolus. Give 100 mg IV slowly over at least 2 minutes; repeat as needed at 2-minute intervals to a maximum dose of 300–500 mg (children: 1–3 mg/kg IV, repeated as needed to a maximum total of 5–6 mg/kg or 150–200 mg).

    2. Intramuscular. Inject 150–200 mg (children: 2–6 mg/kg IM, not to exceed 100 mg) into a large muscle mass (preferably the upper outer quadrant of the gluteus maximus). No more than 5 mL should be administered at an injection site.

    3. Continuous intravenous infusion. Administer a loading dose of 5–6 mg/kg IV over 1 ...

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