Pentobarbital Euthanasia Agents
Pentobarbital sodium, Phenytoin sodium
Also known as: Beuthanasia-D Special · Euthasol · Euthanasia-III · Somnasol · Fatal-Plus · Pentasol · Sleepaway · SP5 · Socumb-6gr · Somlethol · SP6 · Euthanasia solution · Pentobarbital/Phenytoin
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 |
|---|---|---|---|---|---|
| Euthanasia (Pentobarbital sodium single agent) | Approximately 120 mg/kg for the first 4.5 kg of body weight, and 60 mg/kg for every 4.5 kg of body weight thereafter. | IV | Once | — | 🌎 NA |
| Euthanasia (Pentobarbital sodium with phenytoin) | 1 mL for each 4.5 kg of body weight. | IV | Once | — | 🌎 NA |
- Euthanasia (Pentobarbital sodium single agent): Preferably administer IV.
- Euthanasia (Pentobarbital sodium with phenytoin): Beuthanasia-D Special.
Cats
| Indication | Dose | Route | Frequency | Duration | Region |
|---|---|---|---|---|---|
| Euthanasia (Pentobarbital sodium single agent) | Approximately 120 mg/kg for the first 4.5 kg of body weight, and 60 mg/kg for every 4.5 kg of body weight thereafter. | IV | Once | — | 🌎 NA |
| Euthanasia (Pentobarbital sodium with phenytoin) | 1 mL for each 4.5 kg of body weight | IV | Once | — | 🌎 NA |
- Euthanasia (Pentobarbital sodium single agent): Administer IV.
- Euthanasia (Pentobarbital sodium with phenytoin): Not FDA-approved for use in this species.
Horses
| Indication | Dose | Route | Frequency | Duration | Region |
|---|---|---|---|---|---|
| Euthanasia | 10-15 mL per 100 pounds of body weight. | IV | Once | — | 🌎 NA |
- Euthanasia: Depending on product concentration. Must not be used in animals to be consumed.
Cattle
| Indication | Dose | Route | Frequency | Duration | Region |
|---|---|---|---|---|---|
| Euthanasia | 10-15 mL per 100 pounds of body weight. | IV | Once | — | 🌎 NA |
- Euthanasia: Depending on product concentration. Must not be used in animals to be consumed.
Swine
| Indication | Dose | Route | Frequency | Duration | Region |
|---|---|---|---|---|---|
| Euthanasia | 10-15 mL per 100 pounds of body weight. | IV | Once | — | 🌎 NA |
- Euthanasia: Depending on product concentration. Must not be used in animals to be consumed.
Sheep
| Indication | Dose | Route | Frequency | Duration | Region |
|---|---|---|---|---|---|
| Euthanasia | 10-15 mL per 100 pounds of body weight. | IV | Once | — | 🌎 NA |
- Euthanasia: Depending on product concentration. Must not be used in animals to be consumed.
Goats
| Indication | Dose | Route | Frequency | Duration | Region |
|---|---|---|---|---|---|
| Euthanasia | 10-15 mL per 100 pounds of body weight. | IV | Once | — | 🌎 NA |
- Euthanasia: Depending on product concentration. Must not be used in animals to be consumed.
Doses are a clinical reference for licensed veterinary professionals. Always confirm against the current label and the individual patient.
Overview
Pentobarbital-based euthanasia solutions are utilized for the rapid, humane euthanasia of animals not intended for food purposes.
Key Clinical Points:
- Preferred Method: Intravenous (IV) injection of a barbituric acid derivative is the gold standard and preferred method for euthanasia in dogs, cats, other small animals, and horses according to AVMA guidelines.
- Alternative Routes: Intraperitoneal (IP) injection may be used when IV access is distressful or dangerous. Intracardiac (IC) injection must only be used if the animal is heavily sedated, unconscious, or anesthetized.
- Formulations: Some products combine pentobarbital with phenytoin (e.g., Beuthanasia-D Special) to provide added cardiac depressant effects and to alter the regulatory scheduling from a Class-II to a Class-III controlled substance.
Note: Carcasses euthanized with pentobarbital may be rejected by renderers due to tissue residues, and pose a secondary toxicity risk to scavenging wildlife.
Mechanism of action
Pentobarbital is a short-acting barbiturate that acts as a positive allosteric modulator at GABA_A receptors, enhancing the inhibitory effects of GABA.
- At the massive doses used for euthanasia, it causes profound, irreversible central nervous system (CNS) depression.
- This leads to severe depression of the medullary respiratory and vasomotor centers → apnea → hypoxia → cardiac arrest.
Phenytoin (when included) is an antiarrhythmic/anticonvulsant that, at toxic doses, causes direct myocardial depression and cardiovascular collapse, ensuring rapid cessation of cardiac activity.
Safety & warnings
Contraindications
- Animals intended for food purposes (human or animal consumption)
Adverse effects
- Minor muscle twitching post-injection
- Delayed death or incomplete euthanasia if administered perivascularly
- Agonal breathing (terminal gasp)
Precautions
Important Safety Warnings:
- Storage: Must be stored securely so it will not be confused with therapeutic agents. Keep strictly out of reach of children.
- Handling: Exercise extreme care when handling filled syringes. Dispose of used injection equipment properly to prevent accidental human exposure.
- Human Exposure: Avoid any contact with open wounds or accidental injection. Accidental human injection can be fatal.
- Pre-medication: Prior use of a tranquilizing or sedative agent may be necessary and is highly recommended when the animal is in pain, agitated, or fractious.
- Environmental: Renderers may not accept carcasses euthanized with pentobarbital. Proper disposal (e.g., deep burial, cremation) is required to prevent secondary toxicosis in scavenging wildlife (e.g., eagles, coyotes).
Monitoring
- Respiratory rate
- Cardiac rate
- Corneal reflex
Overdose
Not applicable. This agent is specifically designed and administered to induce humane death.
Available products
Formulations
- Injectable solution
- Powder for injection
Veterinary
- Pentobarbital Sodium 390 mg/mL & Phenytoin Sodium 50 mg/mL for Injection (Beuthanasia-D Special, Euthasol, Euthanasia-III Solution, Somnasol)
- Pentobarbital Sodium Powder 392 mg/mL when constituted (Fatal-Plus Powder, Pentasol Powder)
- Pentobarbital Sodium for Injection 260 mg/mL (Sleepaway)
- Pentobarbital Sodium for Injection 324 mg/mL (SP5)
- Pentobarbital Sodium for Injection 389 mg/mL (Socumb-6gr, Somlethol, SP6)
- Pentobarbital Sodium for Injection 390 mg/mL (Fatal-Plus Solution)
Regulatory status
No regulatory data for: 🇺🇸 US · 🇪🇺 EU · 🇬🇧 UK · 🇭🇰 HK · 🇹🇼 TW · 🇯🇵 JP · 🇰🇷 KR · 🇦🇺 AU
Storage & stability
Should be stored in such a manner that these products will not be confused with therapeutic agents. Keep out of reach of children. Controlled substance regulations apply (Class-II or Class-III depending on formulation).
Client information
What to Expect During Euthanasia: Saying goodbye to a beloved pet is incredibly difficult. Understanding the process can help provide some peace of mind.
- Painless Process: The medication acts very quickly, essentially providing a massive overdose of anesthesia. Your pet will fall into a deep, painless sleep within seconds before their heart stops.
- Sedation: The veterinarian will often give a sedative or pain medication first so your pet is completely relaxed and comfortable before the final injection.
- Normal Reflexes: After the pet has passed away, you may notice a few natural reflexes. These are not signs of life or pain, but simply the body relaxing:
- Terminal Gasp: The animal may give a sudden, deep breath or "gasp" after becoming unconscious.
- Muscle Twitches: Minor muscle twitching or spasms may occur.
- Eyes Open: Pets rarely close their eyes when they pass away.
- Loss of Control: The bladder or bowels may release as the muscles completely relax.
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.