Thiopental Sodium
Thiopental sodium
Also known as: Pentothal · Anesthal · Bensulf · Farmotal · Hipnopento · Inductal · Intraval · Nesdonal · Pensodital · Sandothal · Sodipental · Thionembutal · Thiopentax · Tiobarbital · Trapanal · Thiopentone sodium · natrium isopentylaethylthiobarbituricum · penthiobarbital sodique · thiomebumalnatrium cum natrii carbonate · thiopentalum natricum · thiopentobarbitalum solubile · tiopentol sodico
Reviewed by the VetSheet Veterinary TeamUpdated Apr 5, 2026Evidence-based veterinary reference
Doses are a clinical reference for licensed veterinary professionals. Always confirm against the current label and the individual patient.
Dosing by species
🌎 NA — North America🌍 EU — Europe
Dogs
| Indication | Dose | Route | Frequency | Duration | Region |
|---|---|---|---|---|---|
| Anesthesia | 13.2-26.4 mg/kg | IV | once | depending on duration of anesthesia required | 🌎 NA |
| Brief anesthesia (7-10 minutes) | 15-17 mg/kg | IV | once | — | 🌎 NA |
| Moderate anesthesia (10-15 minutes) | 18-22 mg/kg | IV | once | — | 🌎 NA |
| Longer anesthesia (15-25 minutes) | 22-29 mg/kg | IV | once | — | 🌎 NA |
| Anesthesia (unpremedicated) | 22 mg/kg | IV | once | — | 🌎 NA |
| Anesthesia (after tranquilization) | 15.4 mg/kg | IV | once | — | 🌎 NA |
| Anesthesia (after narcotic premedication) | 11 mg/kg | IV | once | — | 🌎 NA |
| Anesthesia induction | 12-15 mg/kg | IV | once | — | 🌎 NA |
- Anesthesia induction: One-third administered rapidly, additional amount to effect
Cats
| Indication | Dose | Route | Frequency | Duration | Region |
|---|---|---|---|---|---|
| Anesthesia | 13.2-26.4 mg/kg | IV | once | depending on duration of anesthesia required | 🌎 NA |
| Anesthesia (unpremedicated) | 22 mg/kg | IV | once | — | 🌎 NA |
| Anesthesia (after tranquilization) | 15.4 mg/kg | IV | once | — | 🌎 NA |
| Anesthesia (after narcotic premedication) | 11 mg/kg | IV | once | — | 🌎 NA |
| Anesthesia induction | 12-15 mg/kg | IV | once | — | 🌎 NA |
- Anesthesia induction: One-third administered rapidly, additional amount to effect
Small Mammals
| Indication | Dose | Route | Frequency | Duration | Region |
|---|---|---|---|---|---|
| Anesthesia (Rabbits) | 15-30 mg/kg | IV | to effect | — | 🌎 NA |
| Anesthesia (Rabbits) | 10-12 mg/kg | IV | to effect | — | 🌎 NA |
| Chemical restraint (Mice) | 50 mg/kg | IP | once | — | 🌎 NA |
| Chemical restraint (Rats) | 40 mg/kg | IP | once | — | 🌎 NA |
| Chemical restraint (Hamsters/Gerbils) | 30-40 mg/kg | IP | once | — | 🌎 NA |
| Chemical restraint (Guinea pig) | 15-30 mg/kg | IV | once | — | 🌎 NA |
| Chemical restraint (Rabbits) | 15-30 mg/kg | IV | once | — | 🌎 NA |
Horses
| Indication | Dose | Route | Frequency | Duration | Region |
|---|---|---|---|---|---|
| Anesthesia (with preanesthetic tranquilization) | 6-12 mg/kg (average 8.25 mg/kg) | IV | once | — | 🌎 NA |
| Anesthesia (without preanesthetic tranquilization) | 8.8-15.4 mg/kg (average 9.9-11 mg/kg) | IV | once | — | 🌎 NA |
| Anesthesia (after xylazine or acepromazine) | 1 gram per 90 kg body weight as a 10% solution | IV | once | — | 🌎 NA |
| Anesthesia (after sedation and guaifenesin) | 5.5 mg/kg | IV | once | — | 🌎 NA |
| Anesthesia (after tranquilization) | 8.8-11 mg/kg | IV | once | — | 🌎 NA |
- Anesthesia (after xylazine or acepromazine): Given evenly over 20 seconds, 15 minutes after premedication
Cattle
| Indication | Dose | Route | Frequency | Duration | Region |
|---|---|---|---|---|---|
| Anesthesia | 8.14-15.4 mg/kg | IV | once | — | 🌎 NA |
| Deep surgical anesthesia (unweaned calves fasted 6-12h) | no more than 6.6 mg/kg | IV | once | — | 🌎 NA |
| Anesthesia (calves under 2 weeks of age) | 15-22 mg/kg | IV | once | 10-12 minutes | 🌎 NA |
| Anesthesia (after sedation and guaifenesin) | 5.5 mg/kg | IV | once | — | 🌎 NA |
| Anesthesia (after tranquilization) | 8.8-11 mg/kg | IV | once | — | 🌎 NA |
- Anesthesia (calves under 2 weeks of age): Administer slowly until complete muscular relaxation
Swine
| Indication | Dose | Route | Frequency | Duration | Region |
|---|---|---|---|---|---|
| Anesthesia | 5.5-11 mg/kg | IV | once | — | 🌎 NA |
| Anesthesia (swine weighing 5-50 kg) | 10-11 mg/kg | IV | once | — | 🌎 NA |
Sheep
| Indication | Dose | Route | Frequency | Duration | Region |
|---|---|---|---|---|---|
| Anesthesia | 9.9-15 mg/kg | IV | once | depending on depth required | 🌎 NA |
Goats
| Indication | Dose | Route | Frequency | Duration | Region |
|---|---|---|---|---|---|
| Anesthesia | 20-22 mg/kg | IV | once | — | 🌎 NA |
- Anesthesia: Given after atropine (0.7 mg/kg) IM
Doses are a clinical reference for licensed veterinary professionals. Always confirm against the current label and the individual patient.
Overview
Thiopental sodium is an ultra-short-acting thiobarbiturate used primarily for the induction of general anesthesia or as a sole anesthetic for very brief procedures.
Clinical Pearls:
- Redistribution Kinetics: Its short duration of action (10-30 minutes) is due to rapid redistribution from the highly perfused CNS to muscle and adipose tissue, rather than rapid metabolism.
- Sight Hound Sensitivity: Greyhounds and other sight hounds exhibit prolonged recoveries due to differences in metabolic handling and lower body fat; alternative induction agents (e.g., propofol, alfaxalone, or methohexital) are generally preferred.
- Tissue Toxicity: Thiopental solutions are highly alkaline (pH > 10). Perivascular extravasation causes severe tissue irritation and necrosis. It must be administered via a secure IV catheter.
- Arrhythmogenic: It can sensitize the myocardium to catecholamines, commonly causing transient ventricular bigeminy in dogs.
Mechanism of action
Thiopental is a highly lipid-soluble thiobarbiturate.
- Mechanism: It binds to the GABA_A receptor complex in the central nervous system.
- Pathway: Binding → increases the duration of chloride ion channel opening → enhances chloride influx → hyperpolarization of the postsynaptic neuronal membrane → profound CNS depression, hypnosis, and anesthesia.
- Due to its high lipid solubility, it rapidly crosses the blood-brain barrier, resulting in anesthesia within 15-30 seconds of IV injection.
Safety & warnings
Contraindications
- Absence of suitable veins for IV administration (Absolute)
- History of hypersensitivity to barbiturates (Absolute)
- Status asthmaticus (Absolute)
- Preexisting leukopenia in horses
- Use with extreme caution or avoid in greyhounds and other sight hounds
- Relative: Severe cardiovascular disease, ventricular arrhythmias, shock, increased intracranial pressure, myasthenia gravis, severe hepatic disease
Adverse effects
- Ventricular bigeminy (dogs)
- Apnea (especially in cats)
- Arterial hypotension
- Excitement and severe ataxia during recovery (horses, if used alone)
- Transient leukopenia and hyperglycemia (horses)
- Vascular dilatation and hypoglycemia (with rapid IV administration)
- Severe tissue necrosis (if administered perivascularly)
- Prolonged recovery with repeated doses
Precautions
WARNING: Thiopental is highly alkaline. Extravasation and intra-arterial injections must be strictly avoided to prevent severe tissue necrosis and CNS toxicity.
- Sight Hounds: Greyhounds metabolize thiobarbiturates much more slowly; prolonged recoveries are common. Consider alternatives.
- Administration: Give strictly to effect. Repeated doses accumulate and significantly prolong recovery.
- Dilution: Do not use concentrations less than 2% in sterile water as they may cause hemolysis.
- Pregnancy: Readily crosses the placental barrier; use with caution (FDA Category C).
Drug interactions
IV clonidine prior to induction may reduce thiopental dosage requirements by up to 37%
May enhance respiratory and CNS depressant effects
Potential for hypotension
Ventricular fibrillatory effects may be potentiated when used with thiobarbiturates and halothane
Given prior to induction may reduce thiopental dosage requirements
May potentiate hypnotic effects
Given prior to induction may reduce thiopental dosage requirements
May potentiate thiopental effects; hypotension possible
May displace thiopental from plasma proteins
Thiopental and sulfas may displace one another from plasma proteins
Monitoring
- Level of hypnosis/anesthesia
- Respiratory status (rate, depth, apnea)
- Cardiac status (heart rate, rhythm, blood pressure)
Pharmacokinetics
Half-life
Absorption
Following IV injection, hypnosis and anesthesia occur within one minute (usually 15-30 seconds).
Distribution
Rapidly enters the CNS due to high lipid solubility, then redistributes to muscle and adipose tissue.
Metabolism
Metabolized by the hepatic microsomal system into several metabolites.
Elimination
Very little of the drug is excreted unchanged in the urine. Elimination half-life in dogs is approximately 7 hours (3-4 hours in sheep).
Overdose
Treatment of thiobarbiturate overdosage consists of:
- Respiratory Support: Provide oxygen (O2) and mechanical ventilation.
- Cardiovascular Support: Provide IV fluids and supportive care.
Note: Do NOT use catecholamines (e.g., epinephrine) as they may induce fatal ventricular arrhythmias in the presence of thiobarbiturates.
Available products
Formulations
- Powder for injection: 2% (20 mg/mL)
- Powder for injection: 2.5% (25 mg/mL)
Veterinary
- None presently being marketed in USA
Human-labeled
- Thiopental Sodium Powder for Injection: 2% (20 mg/mL)
- Thiopental Sodium Powder for Injection: 2.5% (25 mg/mL)
Regulatory status
No regulatory data for: 🇺🇸 US · 🇪🇺 EU · 🇬🇧 UK · 🇭🇰 HK · 🇹🇼 TW · 🇯🇵 JP · 🇰🇷 KR · 🇦🇺 AU
Storage & stability
Dry form is stable indefinitely. Reconstitute only with sterile water, normal saline, or D5W. Concentrations <2% in sterile water should not be used (may cause hemolysis). Reconstituted solutions are stable for 3 days at room temperature and 7 days refrigerated; however, use within 24 hours is recommended as no preservative is present. Do not administer if a precipitate is visible.
Client information
Thiopental is an injectable anesthetic agent used exclusively in a hospital setting by veterinary professionals.
- Monitoring: Your pet will be closely monitored while under anesthesia, including heart rate, breathing, and blood pressure.
- Recovery: Recovery from anesthesia may take several hours. Some breeds, particularly greyhounds and other sight hounds, may experience significantly prolonged recovery times.
- Post-Anesthesia Care: Follow your veterinarian's instructions regarding feeding and activity once your pet goes home.
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.