Pharmacotherapeutic group: Products for animal euthanasia, barbiturates, pentobarbital
ATCvet code: QN51AA01
Pharmacodynamic properties
Pentobarbital sodium is an oxybarbiturate derivative of barbituric acid. Barbiturates depress the entire central nervous system but, quantitatively, various areas are affected differently making the product a potent hypnotic and sedative. The immediate effect is the unconsciousness of deep anaesthesia followed by, at high dose rates, rapid depression of the respiratory centre. Breathing stops and cessation of heart action quickly follows leading to rapid death.
Pharmacokinetic properties
When injected into the bloodstream, a barbiturate ionises, the degree depending on the dissociation constant of the agent and the pH of the blood. Barbiturates bind with plasma proteins, forming an equilibrium of bound and unbound drug in circulating blood. Cell penetration can only occur with the undissociated form.
After cell penetration, dissociation again occurs and binding of the drug to intracellular organelles takes place.
Tissue changes due to cellular penetration and intracellular binding have not been described. In general, the effects on tissues can be categorised as direct and indirect. In general, these effects are subtle and little is known concerning them.
Following intracardiac use unconsciousness is almost immediate and cardiac arrest follows within 10 seconds.
Following intravenous use unconsciousness follows in 5-10 seconds after completion of administration.
Death follows 5-30 seconds later. Intraperitoneally, euthanasia is achieved in 3-10 minutes (due to depression of the respiratory centre, the animal may be clinically dead prior cardiac arrest).