Pentobarbital
Pentobarbital sodium
Also known as: Nembutal · Dolethal · Euthanimal · Euthasal · Euthatal · Euthoxin · Lethobarb · Pentoject · aethaminalum · mebubarbital · mebumal · pentobarbitalum · pentobarbitone · Pentobarbital sodium
Reviewed by the VetSheet Veterinary TeamUpdated Apr 5, 2026Evidence-based veterinary reference
Audited v13 dosing evidence
Reviewed non-calculator evidenceReviewed non-calculator evidence (4)
Evidence only — not for automatic calculation
Crocodilians
TABLE 127.5. Agent: Pentobarbital. Dosage: 7.5–15 mg/kg ICe, or 8 mg/kg IM18,229. Species/Comments: Crocodilians.
Evidence only — not for automatic calculation
Snakes/induction, 30–60 min; duration, ≥ 2 hr; prolonged recovery (risk of occasional fatalities); venomous snakes require twice as much as nonvenomous snakes;18 avoid use in lizards
TABLE 127.5. Agent: Pentobarbital. Dosage: 15–30 mg/kg ICe229. Species/Comments: Snakes/induction, 30–60 min; duration, ≥ 2 hr; prolonged recovery (risk of occasional fatalities); venomous snakes require twice as much as nonvenomous snakes;18 avoid use in lizards.
Evidence only — not for automatic calculation
Chelonians
TABLE 127.5. Agent: Pentobarbital. Dosage: 10–18 mg/kg ICe229. Species/Comments: Chelonians.
Evidence only — not for automatic calculation
Rarely used as an anesthetic agent in reptiles
TABLE 127.5. Agent: Pentobarbital. Dosage: —. Species/Comments: Rarely used as an anesthetic agent in reptiles.
Doses are a clinical reference for licensed veterinary professionals. Always confirm against the current label and the individual patient.
Overview
Pentobarbital is a short-acting oxybarbiturate primarily used in veterinary medicine for general anesthesia, chemical restraint, and the management of refractory status epilepticus.
While historically popular as a general anesthetic, its use has largely been supplanted by safer, more titratable agents (like propofol or alfaxalone) due to its narrow therapeutic index and profound cardiopulmonary depressant effects.
Clinical Pearls:
- Status Epilepticus: Pentobarbital is often used to induce a "barbiturate coma" in patients with refractory seizures. However, it is a general anesthetic with negligible true anticonvulsant properties at standard doses; it stops the physical manifestations of seizures but may not halt the underlying electrical seizure activity in the brain.
- Ventilatory Support: Patients treated with pentobarbital for severe seizures typically require mechanical ventilation and intensive care monitoring due to profound respiratory depression.
- Euthanasia: At significantly higher doses, pentobarbital is the primary active ingredient in most veterinary euthanasia solutions (note: euthanasia dosing is typically covered under separate combination monographs).
- Enzyme Induction: Chronic use strongly induces hepatic cytochrome P450 enzymes, accelerating the metabolism of many concurrent medications.
Mechanism of action
Pentobarbital exerts its profound central nervous system (CNS) depressant effects by interacting with the inhibitory neurotransmitter system.
- GABA_A Receptor Modulation: Binds to the barbiturate site on the GABA_A receptor → increases the duration of chloride channel opening → enhances chloride influx → hyperpolarization of the postsynaptic neuronal membrane.
- Glutamate Inhibition: At higher anesthetic doses, it also depresses the actions of the excitatory neurotransmitter glutamate via AMPA receptors.
- Result: Dose-dependent CNS depression ranging from mild sedation to general anesthesia, coma, and fatal respiratory depression.
Safety & warnings
Contraindications
- Severe hepatic impairment
- Severe respiratory depression or airway obstruction
- Porphyria
- Hypovolemia or severe cardiovascular instability (relative contraindication)
- Intramuscular (IM) administration (painful and slow to act)
- Use of euthanasia-specific solutions for seizure control or anesthesia
Adverse effects
- Profound respiratory depression (apnea)
- Depression of myocardial metabolism
- Vasodilation and decreased venous return
- Hypotension and decreased cardiac perfusion
- Poikilothermia (hypothermia)
- Decreased urinary output
- Seizure-like movements or excitement during recovery from anesthesia
- Excitement and injury during induction/recovery in large animals (especially horses)
- Narcotic excitement (if not premedicated)
- Agonal gasping (reflexive, not a sign of pain)
- Muscle twitching
- Vocalization (rare, usually associated with excitement phase)
Precautions
Cardiopulmonary Depression: Pentobarbital causes dose-dependent respiratory and cardiovascular depression. Patients in a 'barbiturate coma' commonly require mechanical ventilation and intensive care support (e.g., saline infusion and dopamine to manage hypotension).
Individual Variation: There is tremendous individual variation in response when used at standard safe doses. Always titrate to effect.
Laboratory Interference: Barbiturates may cause increased retention of bromosulfophthalein (BSP) and give falsely elevated results. Do not administer within 24 hours before BSP retention tests.
- Equine Use: Generally not considered an ideal agent for adult horses due to the possible development of excitement and injury when the animal is 'knocked down'.
- Tissue Irritation: Highly alkaline (pH 9-10.5); perivascular injection can cause severe tissue necrosis.
Drug interactions
Decreased effect by lowering serum concentration (due to hepatic enzyme induction)
Decreased effect by lowering serum concentration
Decreased effect by lowering serum concentration
Decreased effect by lowering serum concentration
Decreased effect by lowering serum concentration
Decreased effect by lowering serum concentration
Decreased effect by lowering serum concentration
Decreased effect (may persist for weeks after barbiturate is discontinued)
Decreased effect by lowering serum concentration
Decreased effect by lowering serum concentration
Decreased effect by lowering serum concentration
Decreased effect by lowering serum concentration
Decreased effect by lowering serum concentration
Decreased effect by lowering serum concentration
Decreased effect by lowering serum concentration
Decreased effect by lowering serum concentration
Decreased effect by lowering serum concentration
Decreased effect by lowering serum concentration
Decreased effect by lowering serum concentration
Increase the CNS depressant effect of pentobarbital
Increase the CNS depressant effect of pentobarbital
Monitoring
- Levels of consciousness and/or seizure control
- Respiratory rate, rhythm, and depth (capnography and pulse oximetry highly recommended)
- Cardiac signs (heart rate, blood pressure, ECG)
- Body temperature (monitor for poikilothermia)
- Routine blood counts and liver function tests (if used chronically)
- Absence of heartbeat (auscultation)
- Absence of respiration
- Loss of corneal reflex
- Pupillary dilation
Pharmacokinetics
Half-life
Absorption
Rapidly absorbed following oral or intraperitoneal administration.
Distribution
Highly lipid soluble; rapidly crosses the blood-brain barrier to exert CNS effects. It subsequently redistributes from the brain to highly perfused tissues, and eventually to muscle and fat, which terminates its initial anesthetic effect.
Metabolism
Extensively metabolized in the liver via cytochrome P450 enzymes. Chronic administration induces these enzymes, accelerating its own metabolism and that of other drugs.
Elimination
Metabolites are primarily excreted by the kidneys.
Overdose
Overdose of pentobarbital leads to profound central nervous system depression, progressing rapidly to coma, severe respiratory depression (apnea), cardiovascular collapse, and death.
- Treatment: There is no specific reversal agent for barbiturates. Treatment is entirely supportive.
- Interventions: Immediate intubation and mechanical ventilation are required. Intravenous fluids and vasopressors (e.g., dopamine) should be administered to support blood pressure and cardiac output. Maintain body temperature to prevent severe hypothermia.
Available products
Formulations
- Injection (50 mg/mL)
- Suppositories
- Injectable: 200 mg/ml non-sterile aqueous solution
- Injectable: 400 mg/ml non-sterile aqueous solution
- Injectable: 500 mg/ml non-sterile aqueous solution
Veterinary
- Dolethal 200 mg/ml solution for injection
- Euthanimal 200 mg/ml / 400 mg/ml solution for injection
- Euthasal 400 mg/ml solution for injection
- Euthatal 200 mg/ml solution for injection
- Euthoxin 500 mg/ml solution for injection
- Lethobarb 200 mg/ml solution for injection
- Pentoject 200 mg/ml solution for injection
Human-labeled
- Pentobarbital Sodium Injection: 50 mg/mL in 2 mL Tubex; generic; (WyethAyerst); (Rx, C-II)
Regulatory status
Carcasses must not enter the food chain.
POM-V CD SCHEDULE 3. Safe custody requirements apply.
No regulatory data for: 🇺🇸 US · 🇭🇰 HK · 🇹🇼 TW · 🇯🇵 JP · 🇰🇷 KR · 🇦🇺 AU
Storage & stability
The injectable product should be stored at room temperature; suppositories should be kept refrigerated. The aqueous solution is not very stable and should not be used if it contains a precipitate. Because precipitates may occur, pentobarbital sodium should not be added to acidic solutions.
Client information
This medication is a powerful sedative and anesthetic.
- Hospital Use: It is almost exclusively used in a veterinary hospital setting under close professional supervision, often in an intensive care unit.
- At-Home Use: If oral dosage forms are dispensed for home use, strict adherence to the veterinarian's dosing instructions is critical. Overdoses can be fatal.
- Safety: Keep this medication in a secure, child-resistant container, completely out of reach of children and other pets. It is a strictly controlled substance.
VetSheet drug reference is intended for licensed veterinary professionals as a clinical decision-support aid, not a substitute for professional judgement or the manufacturer’s current label.