Pharmacokinetics of intraperitoneal infusion of lidocaine in horses

Abstract

The objective of this study was to describe the pharmacokinetics of intraperitoneal (IP) lidocaine in horses (30mg/kg). The study was designed as double blinded cross-over, placebo controlled clinical trial, with a 2 weeks washout period. All horses were part of the research herd of the Auburn University Large Animal Teaching Hospital. Four healthy adult, mixed breed horses, 8 to 15 years of age, that weighed between 490 and 570 kg were randomly assigned to receive either placebo or lidocaine first. A solution of 5 liters of balanced electrolyte solution with or without 2% lidocaine at a dose of 30 mg/kg was injected IP over 20 minutes. Horses were monitored for 24 hours after IP infusion for signs of toxicity. Blood was collected at 0, 5, 10, 15, 30, 45, 60, 75, 90, 120, 150, 180, 240, 300, 360, 480, and 1440 minutes after infusion. Samples of peritoneal fluid (PF) were obtained at minutes 0, 60, 120, 360 and 1440 minutes. Lidocaine and its active metabolite monoethylglycinexylidide (MEGX) were quantified in plasma and PF using high performance liquid chromatography. Time versus concentration data were subjected to non-compartmental analysis. Peak plasma (Cmax) lidocaine and MEGX concentrations were 2.82 ± 0.84μg/ml and 5.58 ± 3.78 μg/ml, respectively; time to maximum concentration was 75 ± 71 min and 93 ± 98 min respectively. Plasma lidocaine concentration remained above 1 μg/ml for 2 hours and declined to non-quantifiable concentration (< 0.2 μg/ml) by 8 hours after infusion. For IP, Cmax for lidocaine and MEGX were 2.82 ± 0.84 and 5.58 ± 3.78 μg/ml, respectively. Clinical signs indicative of lidocaine adversity occurred in one horse after IP administration of lidocaine; this horse recovered completely in 45 minutes without intervention. Further studies are indicated to ` III establish an IP dose of lidocaine necessary to achieve its target effects without causing adverse effects.