Effects of halothane on the pharmacokinetics of lidocaine in digitalis-toxic dogs.

Following the production of digitalis toxicity in dogs as manifested by ventricular tachycardia, the pharmacokinetics of lidocaine treatment of the arrhythmia were determined during pentobarbitone anaesthesia and pentobarbitone-halothane anaesthesia. The elimination rate constants, beta and Ke, and the biological half life T1/2beta were statistically significantly increased during halothane anaesthesia. The volume of distribution was unchanged. The results indicate that the therapeutic loading dose of lidocaine need not be altered during halothane anaesthesia but if a constant infusion is used, the rate of infusion would have to be decreased four fold to avoid toxic plasma levels of lidocaine.