Thiopental Sodium: veterinary dose and monograph

At a glance

Drug class

Sedative / anaesthetic

Also known as

Thiopentone, Pentothal, Intraval

Species with doses

Dogs, Cats, Cattle, Horses, Sheep and Pigs

General dose range

10–20 mg/kg IV single induction dose (to effect) — check the species tables for the indication

Routes

IV

Last reviewed

1 October 2026

Indications

• Rapid IV induction of general anaesthesia (to allow intubation)
• Control of refractory status epilepticus (anaesthetic-dose barbiturate)
• Short procedures requiring brief anaesthesia (historical)

Thiopental Sodium dose by species

Doses are per administration unless stated. mg/kg doses scale with body weight; per-animal, per-quarter and infusion-rate doses are shown as the reference writes them.

Dogs

• Induction (to effect): Given strictly to effect. Papich 5e: 10–25 mg/kg IV. Plumb’s p.1112: label 13.2–26.4 mg/kg by desired duration; 12–15 mg/kg with one-third given rapidly then to effect (Hellyer); 15.4 mg/kg after tranquillisation, 11 mg/kg after opioid premedication (Mandsager). Perivascular injection causes sloughing — use a catheter. Avoid in sighthounds (prolonged recovery).

Cats

• Induction (to effect): Given strictly to effect. Papich 5e: 5–10 mg/kg IV. Plumb’s p.1112: 12–15 mg/kg, one-third rapidly then to effect (Hellyer); after tranquillisation 15.4 mg/kg, after opioid premedication 11 mg/kg (Mandsager).

Cattle

• Induction: Papich 5e: 6–12 mg/kg IV to effect. Plumb’s p.1112: 8.14–15.4 mg/kg IV (label); 5.5 mg/kg after sedation + guaifenesin; fasted unweaned calves no more than 6.6 mg/kg. Intubate — regurgitation risk. Extra-label — FARAD withdrawal.

Horses

• Induction (with sedation/GGE): Plumb’s p.1112: with tranquillisation 6–12 mg/kg IV (average 8.25) (label); 5.5 mg/kg after sedation and guaifenesin; 8.8–11 mg/kg after tranquillisation (Mandsager). ARCI Class 2.

Sheep

• Induction (to effect): Plumb’s p.1112 (label): sheep 9.9–15 mg/kg IV by depth required. Intubate. Obtain a FARAD withdrawal.

Pigs

• Induction (to effect): Papich 5e: pigs 10–20 mg/kg IV to effect. Plumb’s p.1112: 5.5–11 mg/kg IV (label); 10–11 mg/kg for 5–50 kg pigs (Booth). Obtain a FARAD withdrawal.

Buffalo

No buffalo-specific doses are on file, so buffalo are dosed as cattle.

• Induction: Papich 5e: 6–12 mg/kg IV to effect. Plumb’s p.1112: 8.14–15.4 mg/kg IV (label); 5.5 mg/kg after sedation + guaifenesin; fasted unweaned calves no more than 6.6 mg/kg. Intubate — regurgitation risk. Extra-label — FARAD withdrawal.

Contraindications

Sighthounds / very lean animals (prolonged recovery — avoid or greatly reduce dose). Perivascular injection (necrosis — IV only, ideally via catheter). Severe cardiovascular/respiratory compromise, shock, hypovolaemia (profound depression). Caesarean (neonatal depression). Significant hepatic disease. Known barbiturate hypersensitivity.

Species-specific warnings

Dogs: Sighthounds (Greyhounds, Salukis, etc.) have markedly prolonged, rough recoveries — avoid thiopental or use a greatly reduced dose with propofol/alfaxalone preferred.

Adverse effects

• Dose-dependent apnoea and respiratory depression
• Myocardial depression, hypotension, arrhythmias (bigeminy common)
• Severe perivascular necrosis if extravasated
• Prolonged recovery in sighthounds/lean animals; excitement on recovery without premed

Drug interactions

• Other CNS depressants/anaesthetics/opioids: additive depression — reduce dose
• Acidic/incompatible drugs in line: precipitation (alkaline solution)
• Highly protein-bound — hypoproteinaemia/acidosis increases free (active) drug and effect
• Sulphonamides: displacement increases free thiopental

Pregnancy and lactation

Crosses the placenta and depresses neonates at caesarean — avoid or minimise; propofol/alfaxalone are preferred for caesarean.

Monitoring

• Respiration/airway (intubate; apnoea common at induction), SpO2/capnography
• Heart rate/rhythm (ECG — bigeminy) and blood pressure
• IV catheter patency (avoid perivascular injection)
• Recovery quality/duration (sighthounds prolonged)

Toxicity and overdose

Overdose causes profound respiratory depression/apnoea, severe hypotension and cardiovascular collapse; recovery is prolonged in lean/sighthound patients. Extravasation causes severe tissue necrosis/sloughing. There is no reversal agent — support is the mainstay.

Management: No antidote. Support ventilation/oxygenation (intubate and ventilate for apnoea) and circulation (IV fluids, vasopressors/inotropes); ECG monitoring. For extravasation, infiltrate the site (dilution ± local lidocaine/saline) and treat as a caustic extravasation. Recovery requires time/support.

Clinical pearls

• Titrate IV to effect via a secure catheter — extravasation causes nasty necrosis, and giving the whole calculated dose at once risks apnoea/collapse
• AVOID in Greyhounds/sighthounds (and very lean animals): recovery is prolonged because the drug relies on redistribution into fat
• No reversal — be ready to intubate and ventilate; premedication smooths induction and recovery
• Largely superseded by propofol/alfaxalone, but still used where those are unavailable and in some equine protocols

Mechanism of action

A thiobarbiturate that potentiates GABA-A receptor activity (prolonging chloride-channel opening) and, at higher concentrations, directly activates the channel — producing rapid, profound CNS depression and anaesthesia. Its high lipid solubility gives near-instant brain penetration (fast induction); anaesthesia ends mainly by REDISTRIBUTION from brain to other tissues (fat/muscle), not metabolism — which is why lean sighthounds, with little fat to redistribute into, recover slowly.

Formulations and products

• Powder for injection 0.5 g / 1 g vial (reconstitute to 1.25–2.5 %)
• Reconstituted solution 25 mg/mL (2.5 %)
• Thiosol / Anesthal / Pentothal — 0.5 g / 1 g vial (reconstitute), Injection (human-label)

Storage

Powder: 15–30 °C. Reconstituted solution: refrigerate and use within ~24–48 h (no preservative); discard if precipitated. Alkaline — keep separate from acidic drugs in the line.

Before you use this dose

Reference doses for veterinary professionals. Confirm the dose against the product label, the patient’s condition, current guidance and local regulations before use; the attending veterinarian remains responsible for every clinical decision.

Other sedatives and anaesthetics

• Phenobarbital
• Propofol
• Romifidine
• Sevoflurane
• Tiletamine–Zolazepam
• Trazodone
• Xylazine

Frequently asked questions