Pentobarbital

Pentobarbital is a short-acting barbiturate with sedative, anesthetic and anticonvulsant properties. Its use as a routine veterinary general anesthetic has declined, but it remains relevant in selected laboratory-animal procedures, refractory seizure treatment and authorized euthanasia formulations. The clinical effect changes with exposure, from sedation to profound central nervous system depression.

Group

Barbiturate anesthetic

Mechanism of Action

Pentobarbital enhances GABA-A-receptor-mediated inhibitory neurotransmission, principally by prolonging chloride-channel opening. At higher concentrations it produces broader central depression, including effects on excitatory signaling and direct channel activity. Reduced neuronal excitability explains anticonvulsant and anesthetic effects. At euthanasia exposure, profound depression leads to loss of consciousness followed by respiratory and cardiovascular arrest.

Dose Rates

Dogs

Use / stage	Dose	Route	Schedule	Instructions
General anesthesia	25–30 mg/kg	IV	Once	Titrate to effect, with respiratory support available.
Anesthetic infusion — Loading	2–15 mg/kg	IV	Once	Titrate before starting maintenance infusion.
Anesthetic infusion — Maintenance	0.2–1 mg/kg/hour	IV	Continuous
Status epilepticus	2–6 mg/kg	IV	As needed	Allow 15-20 minutes for full response before reassessment.
Euthanasia	87 mg/kg	IV	Once	Euthanasia only. Approximate pentobarbital amount described for 390 mg/mL euthanasia solution at 1 mL/4.5 kg. Dedicated combination products must retain their full composition.
Sedation	2–4 mg/kg	IV
Sedation	2–4 mg/kg	PO	Every 6 h
Ventilator chemical restraint	1–3 mg/kg/hour	IV	Continuous
General anesthesia	10–30 mg/kg	IV	Once	Titrate to effect.
General anesthesia	24–33 mg/kg	IV	Once	Titrate to effect.
Refractory seizure motor suppression	3–15 mg/kg	IV		Heavy CNS depression may suppress movement without abolishing cerebral seizure activity; ventilation may be required.
Refractory seizure motor suppression	2–15 mg/kg	IV		Heavy CNS depression may suppress movement without abolishing cerebral seizure activity; ventilation may be required.

Cats

Use / stage	Dose	Route	Schedule	Instructions
General anesthesia	25–30 mg/kg	IV	Once	Titrate to effect, with respiratory support available.
Anesthetic infusion — Loading	2–15 mg/kg	IV	Once	Titrate before starting maintenance infusion.
Anesthetic infusion — Maintenance	0.2–1 mg/kg/hour	IV	Continuous
Status epilepticus	2–6 mg/kg	IV	As needed	Allow 15-20 minutes for full response before reassessment.
Euthanasia	87 mg/kg	IV	Once	Euthanasia only. Approximate pentobarbital amount described for 390 mg/mL euthanasia solution at 1 mL/4.5 kg. Dedicated combination products must retain their full composition.
Sedation	2–4 mg/kg	IV
Sedation	2–4 mg/kg	PO	Every 6 h
Ventilator chemical restraint	1–3 mg/kg/hour	IV	Continuous
Status epilepticus	5–15 mg/kg	IV		To effect.
Status epilepticus	3–15 mg/kg	IV	Every 4–8 h	Slow administration; target heavy sedation.
General anesthesia	25 mg/kg	IV	Once	Additional 10 mg/kg IV reported if induction inadequate.

Cattle

Use / stage	Dose	Route	Schedule	Instructions
Standing sedation	1–2 mg/kg	IV	Once
General anesthesia	20–30 mg/kg	IV	Once	Administer to effect.
Chlorinated hydrocarbon toxicosis adjunct	30 mg/kg	IV	As needed	Titrate to effect.
Calf anesthesia	15–30 mg/kg	IV		Calves over 1 month of age.
Standing sedation fixed alternative	1–2 g/animal	IV		Adult cow; titrate until unsteady. Approximately 3 g may cause recumbency.

Sheep

Use / stage	Dose	Route	Schedule	Instructions
General anesthesia	20–30 mg/kg	IV	Once	Administer to effect.
Adult anesthesia	11–54 mg/kg	IV		Average reported amount 24 mg/kg; duration affects need for supplementation.
Lamb anesthesia	15–26 mg/kg	IV		An additional 5.5 mg/kg IV reportedly extends anesthesia by about 30 minutes.

Goat

Use / stage	Dose	Route	Schedule	Instructions
General anesthesia	20–30 mg/kg	IV	Once	Administer to effect.
General anesthesia	25 mg/kg	IV		Slowly; reported satisfactory duration about 20 minutes.

Mice

Use / stage	Dose	Route	Schedule	Instructions
Chemical restraint or anesthesia	30–80 mg/kg	IP	Once

Rats

Use / stage	Dose	Route	Schedule	Instructions
Chemical restraint or anesthesia	40–60 mg/kg	IP	Once

Hamsters

Use / stage	Dose	Route	Schedule	Instructions
Chemical restraint or anesthesia	70–80 mg/kg	IP	Once

Gerbils

Use / stage	Dose	Route	Schedule	Instructions
Chemical restraint or anesthesia	70–80 mg/kg	IP	Once

Guinea pigs

Use / stage	Dose	Route	Schedule	Instructions
Chemical restraint or anesthesia	15–40 mg/kg	IP	Once
Chemical restraint or anesthesia	30 mg/kg	IV	Once

Rabbits

Use / stage	Dose	Route	Schedule	Instructions
Chemical restraint or anesthesia	20–60 mg/kg	IV	Once

Pigs

Use / stage	Dose	Route	Schedule	Instructions
Chemical restraint or anesthesia	15–30 mg/kg	IV	Once

Horses

Use / stage	Dose	Route	Schedule	Instructions
Chemical restraint or anesthesia	3–15 mg/kg	IV	Once	Adult equine excitement/recovery injury makes this a less suitable agent.
Chemical restraint or anesthesia	15–18 mg/kg	IV	Once	Adult equine excitement/recovery injury makes this a less suitable agent.

Indications

General anesthesia or chemical restraint in selected veterinary or laboratory-animal procedures.
Specialist control of refractory status epilepticus or severe toxin-associated convulsions within a supported critical-care protocol.
Veterinary euthanasia using an authorized preparation and procedure.

Contraindications

Rapid IV injection can cause fatal apnea; narrow therapeutic index.

Interactions

Other anesthetics potentiate depression; hepatic enzyme inducers or inhibitors can alter clearance.

Adverse effects

Respiratory and cardiovascular depression.

Toxicity

Overdose causes respiratory arrest and cardiovascular collapse. Overdose causes coma, respiratory failure and cardiovascular collapse. Support airway and circulation; carcasses containing euthanasia drug can poison scavenging animals. Enhanced elimination may be considered in severe poisoning.

Preparations

Preparation	Form	Strength	Route
Pentobarbital sodium anesthetic injection 50 mg/mL Anesthetic formulation; not an interchangeable euthanasia mixture.	Injection	50 mg / mL	IV
Pentobarbital sodium anesthetic injection 65 mg/mL Anesthetic formulation; not an interchangeable euthanasia mixture.	Injection	65 mg / mL	IV

Monitoring and Administration

Provide airway support and monitor ventilation, pulse and rhythm. For anesthesia, give about half the calculated amount first and titrate the remainder.

Alkaline injection precipitates with acidic/hydrochloride drugs. Euthanized carcasses retain pentobarbital and must be kept from scavengers.

Ventilator restraint may involve separate opioid or benzodiazepine infusions. Long recovery and seizure-like movements may complicate weaning; a shorter-acting agent can be substituted before ventilator withdrawal.