DISPOSITION KINETICS OF KETAMINE IN DOMESTIC CAT

  • 1 January 1976
    • journal article
    • research article
    • Vol. 220  (1) , 115-124
Abstract
The disposition kinetics and systemic availability of ketamine, a dissociative anaesthetic agent, was studied in normal domestic cats. A similar ketamine hydrochloride dose (25 mg/kg) was administered by the i.v. and i.m. routes; drug concentrations in plasma were measured by GLC. A rapid distribution half-life phase (t1/2(.alpha.) = 3 min) was followed by a slower 1st-order elimination phase. The half-life of the drug (66.9 .+-. 24.1 min) was independent of the parenteral administration route. Absorption from i.m. site of administration was rapid, with peak plasma level at 10 min, and about 92% of the dose was available systemically. Plasma protein binding, measured in vitro at 5 and 20 .mu.g/ml by equilibrium dialysis technique, was 53% and independent of ketamine concentration. Simulated plasma and tissue level curves, which were generated by an analogue computer programmed with the individual rate constants of the 2-compartment open model, showed that 10 and 15% of the dose were present in the central and peripheral compartments, respectively, at 90 min after i.v. drug administration. Peak tissue level of 42% of the dose was reached at 12-15 min. Parenteral administration of ketamine, at the dosage rate studied, quickly produced an immobilizing effect of variable duration (0.75-1.75 h) in normal cats.

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