PHARMACOKINETICS OF LIGNOCAINE IN ICELANDIC HORSES AFTER INFILTRATIONANESTHESIA

The pharmacokinetics of lignocaine was studied in four Icelandic horse s after infiltration anaesthesia. A total of 240 mg of the drug was in jected on either side of the left foreleg, over the medial and lateral branches of the palmar nerve. Blood samples were collected up to seve n hours after injection and the concentrations of the drug in plasma w ere determined by gas chromatography/mass spectrometry. The results sh elved that lignocaine was rapidly absorbed. A mean maximum concentrati on of 232 ng/ml was observed after 20 minutes. In three of the horses the decline in the plasma concentration of the drug with time was best described by the sum of two exponential terms, but in one of the hors es the decline was monoexponential. The mean half-life of the distribu tion phase (alpha) was 9.8 minutes and that of the elimination phase ( beta) 48.4 minutes. In all the horses the plasma concentration was bel ow the limit of detection (2 ng/ml) six hours after injection. Anaesth esia was tested in one horse and lasted for one hour.