Pharmacokinetic analysis of intravenously and orally administered quinidine in cows

Seven healthy adult cows weighing between 550 and 750 kg were administered quinidine gluconate (5 mg/kg) IV and quinidine sulfate (15,84 mg/kg) orally to determine pharmacokinetic values. The apparent volume of distribution was 3.80 +/- 2.21 L/kg. Total body clearance was 19.0 +/- 7.02 ml/min/kg and plasma half-life was 2.25 +/- 0.68 hours. The systemic availability of quinidine sulfate after oral administration of a 20 mg/kg dose was 23.3 +/- 16.3%. The mean peak plasma concentration reached in 7 cows after oral administration of quinidine sulfate was 0.26 micrograms/ml. The peak plasma quinidine concentration was reached in an average of 41 minutes after oral administration. The average plasma quinidine concentration 5 minutes after IV administration of quinidine gluconate was 27.5 +/- 22.1 micrograms/ml. At this time, some of the cows showed signs of quinidine toxicosis. The application of pharmacokinetic determinations to the clinical use of quinidine in cows is discussed.