pentobarbital euthanasia dose
Pentobarbital is an oxybarbiturate analog of barbituric acid. Pentobarbital can be utilized as a sedative–hypnotic, anesthetic, and anticonvulsant. Pentobarbital’s mechanism of action is similar to that of benzodiazepines and propofol in that GABAA receptors are activated resulting in enhanced GABA binding and opening of transmembrane chloride channels leading to cellular hyperpolarization within the central nervous system. Administration of pentobarbital produces dose-dependent sedation, hypnosis, muscle relaxation, and depression of the sensory cortex and reticular activating system.
As with all GABAA agonists, pentobarbital has little or no analgesic activity. Pentobarbital produces dose-dependent respiratory depression which may require respiratory assistance (Peeters et al., 1988). At higher doses, pentobarbital possesses anticonvulsant and hypotensive properties. Hypotension results from vasodilation, diminished myocardial contractility, and reduced cardiac output. These and other cardiovascular effects depend upon the route of administration and tend to be less pronounced with IP rather than IV administration. This is due to the fact that peak blood concentration is reached more slowly than with IV administration and the portion of drug absorbed into the portal system is subject to early destruction in the liver. Hypothermia is common and has been reported in gerbils (Weinandy et al., 2005). Hypothermia is most likely a result of decreased basal metabolism and vasodilation. Additive sedation and respiratory depression can occur if pentobarbital is administered in conjunction with tranquilizers, benzodiazepines, opioids, alpha2-agonists, propofol, and inhalant anesthetic agents. Animals administered pentobarbital should be supplied supplemental oxygen or monitored with pulse oximetry. General anesthetic doses may require respiratory support or endotracheal intubation.
When pentobarbital is administered, a supplemental heat source should be applied to the animal during the surgical period and continued until full recovery to prevent hypothermia. Pentobarbital can be administered intraperitoneally or intravenously. When used as a general anesthetic, pentobarbital can be administered as a bolus (Borkowski et al., 1990) or CRI. Commercial solutions commonly contain propylene glycol, which can cause pain upon injection and thrombophlebitis. For this reason, the subcutaneous and intramuscular routes of injection are not recommended.