Pentobarbital

Pentobarbital is a short- to intermediate-acting barbiturate with central nervous system depressant effects. It is used clinically as a sedative-hypnotic, pre-anesthetic medication, and, in higher doses, as an anesthetic. It is also used intravenously for the treatment of refractory seizures in emergency settings and, in veterinary medicine, for euthanasia. In some jurisdictions it is employed as part of humane euthanasia protocols in humans.

Pharmacology and mechanism of action: Pentobarbital enhances GABA-A receptor activity, increasing chloride influx and producing CNS depression. It is highly lipophilic, enabling rapid entry into the brain after intravenous administration, with onset typically within 30 seconds to a minute. The duration of the hypnotic effect is usually several hours, depending on dose, formulation, and individual factors. It is metabolized by the liver and excreted by the kidneys; active metabolites may contribute to prolonged effects, especially in elderly or hepatic-impaired patients.

Administration and clinical uses: In the clinical setting, it may be given IV for rapid induction of anesthesia or sedation; for refractory seizures IV pentobarbital is used when benzodiazepines and conventional anticonvulsants have failed. It can be used in supervised coma therapy for intracranial hypertension. In veterinary medicine, it is commonly used for humane euthanasia.

Adverse effects and safety: The major risks are respiratory depression, hypotension, bradycardia, and coma, particularly at high doses or with coexisting CNS depressants. It can cause dependence and withdrawal with repeated use. Contraindications include acute porphyria and significant respiratory or cardiac compromise. Pentobarbital is a controlled substance in many jurisdictions, reflecting its potential for abuse and safety concerns.