Conserving pentobarbital in times of shortage

As a means to address the current shortage of pentobarbital euthanasia solutions and extend available supplies, veterinarians might consider combining the use of pentobarbital-containing euthanasia solutions with deep general anesthesia to perform in-clinic and in-home euthanasia.

Due to limited availability of the active pharmaceutical agent, there is a shortage of Schedule II and Schedule III pentobarbital euthanasia solutions (e.g., Beuthanasia-D^®; Euthasol^®; Fatal-Plus ^®).

Each ml of Schedule II and Schedule III pentobarbital euthanasia solutions contains 390 mg of pentobarbital. The labelled product dosing is 1 ml/10 lbs body weight (39 mg/lb) or 1 ml/4.5 kg (87 mg/kg), administered IV. These doses represent approximately 3 times the dose of pentobarbital necessary to produce general anesthesia when administered as the sole agent. Intravascular administration of Schedule II and Schedule III products at the labelled dose creates an anesthetic overdose, with severe respiratory depression and apnea preceding death.

During the shortage, using these pentobarbital-containing euthanasia solutions in combination with deep general anesthesia could be on option for in-clinic and in-home euthanasia. A deep state of general anesthesia is necessary to augment any reduction in the administered dose of pentobarbital.

One reportedly successful combination includes inducing general anesthesia with IV propofol, 4-6 mg/kg (2-3 mg/lb), followed by 1/2 of the usual dose of pentobarbital euthanasia solution administered IV:

• For a 10 lb (4.5 kg) dog or cat, this works out to 2-3 ml of propofol (20-30 mg) followed by 0.5 ml (195 mg) of Schedule II- Schedule III pentobarbital euthanasia solution.
• For a 20 lb (9.1 kg) dog, a 1:1 mixture of midazolam + ketamine (0.275 mg/kg midazolam, 5.5 mg/kg ketamine), administered IV could be followed by 1 ml (390 mg) of Schedule II-Schedule III pentobarbital euthanasia solution.

Erring on the high side for dosing the IV general anesthetic is recommended when performing euthanasia. Other agents producing a deep state of general anesthesia (e.g., IV alfaxalone or Telazol®, with appropriate pre-sedation) should produce similar results. Reduction of the pentobarbital dose beyond 1/2 of the labeled dose may not be sufficient to cause death and is not recommended.

Careful monitoring is required to confirm death and ensure that the animal is not simply in a prolonged state of general anesthesia. An additional method of assuring death may be necessary in some cases.

See other potential alternatives based on the AVMA Guidelines for Euthanasia of Animals: 2020 Edition.