Pharmacokinetic analysis of antimicrobials and an anthelmintic agent in alpacas and llamas with theoretical applications

The pharmacokinetics of two antimicrobials were investigated in alpacas. Six healthy alpacas were each administered a single dose of 10 mg/kg of oxytetracycline by IV injection and IM injection. In addition, a single dose of 20 mg/kg of florfenicol by IV administration was given to alpacas in a separate study. The pharmacokinetic parameters of oxytetracycline and florfenicol in alpacas were compared to the results previously obtained in llamas. There were significant differences between llamas and alpacas in several of oxytetracycline pharmacokinetic parameters but there were no significant differences in all of florfenicol pharmacokinetic parameters in these two animals. It can be concluded that llamas and alpacas have different oxytetracycline disposition kinetics while they have similar disposition kinetics of florfenicol. The pharmacokinetics of clorsulon, a narrow-spectrum anthelmintic agent, was investigated in llamas following oral administration at a single dose of 14 mg/kg. The plasma levels of clorsulon produced by this dose was lower than the values reported in the clorsulon pharmacokinetic studies carried out in sheep and goats following oral administration at a single dose of 7 mg/kg This suggests the entire dose of clorsulon is not absorbed in llamas. Since the differential equations describing one-compartment system with first-order input and two-compartment system after IV administration with nonlinear elimination kinetics cannot be solved, there is no mathematical expression for the AUC for drugs following these models. The AUC values calculated from the proposed preliminary AUC equations for drugs following these models were compared to the AUC calculated using the trapezoidal rule method based on computer-generated data using the fourth-order Runge-Kutta method. Except for a few exceptions, the predicted AUC from the proposed equations matched the values calculated from the theoretically generated data