Lignocaine kinetics in the rat.

After intravenous injection of lignocaine 2.5, 5.0 or 10.0 mg kg-1 in the rat blood concentration declined in a bi-exponential m anner. The data were analysed according to a two-compartment open model with elimination from the central compartment. Analysis of variance revealed no significant differences in k12, k21, k13, t 1/2 alpha, t 1/2 beta, AUC or in the volume constants for the different doses used. After lignocaine 50.0, 70.0 or 90.0 mg kg-1 by mouth there was no significant change in t 1/2 beta for the different doses or in peak plasma concentration normalized for dose. For both routes of administration blood concentration-time curves were superimpossible and AUC was linearly related to dose. Renal excretion was negligible. Systemic availability of lignocaine was the lowest of species so far studied (mean 0.019 +/- 0.001) did not alter with dose, and was very similar to the values in the literature quoted for the isolated perfused liver. Clearance of lignocaine related to anticipated liver mass was almost identical to the values for liver blood flow quoted using other techniques. The data indicated high hepatic extraction of lignocaine by the intact rat and the absence of dose dependency within the range studied.