Hanna, R.M., Borchard, R.E.&Schmidt, S.L. Pharmacokinetics of ketamine HC1 and metabolite I in the cat: a comparison of i.v., i.m., and rectal administration.J. vet. Pharmacol. Therap.11, 84–93.Ketamine HC1 [2‐(o‐chlorophenyl)‐2‐(methylamino) cyclohexanone HC1] concentrations in whole blood were used to study the pharmacokinetics of i.v., i.m., and rectal administrations, at a dose of 25 mg/kg, in normal domestic cats. Absorption was rapid with both the i.m. and rectal routes. Systemic availability was 51% (SEM 10) for the i.m. dose and 43.5% (SEM 6.1) for the rectal dose. The first‐pass effect had a minimal influence on the metabolism of ketamine HC1 administered rectally. The elimination rate constant (β) of the drug was statistically similar in the i.v., i.m., and rectal groups, at a 95% level of significance (P<0.05). At the dosage rates studied, ketamine HC1 produced an anesthetic effect in the cat following i.v., i.m. and rectal ad