Serum Levels and Half-Life of Carbaryl in Buffalo Calves after Subchronic Exposure:Implications for Withdrwal Times

Abstract

Carbaryl is recommended for use on fodders crops in India, but absolutely no work has been done on its toxicokinetics aspect in any species consuming these forage crops, including buffalo species. Since the toxicokinetics serves as a basis for recommending safe withdrawal period of any substance, the aim of this study was to compute important parameters of carbaryl after its subchronic exposure at recommended dose in order to serve as a guideline with regards to observation of meat withdrawal times in buffaloes exposed to carbaryl. Carbaryl was given at the dose rate of 1 mg/kg daily for 105 consecutive days and blood samples of each animal were collected, followed for extraction of carbaryl in serum. Carbaryl produced a gradual accumulation in serum of buffalo calves after oral exposure. There was variation in serum carbaryl levels from 3.31 ± 0.28 to 3.46 ± 0.61 ppm through day 15 to day 105 of exposure, respectively. The area under the curve (AUC) was computed to be 363.0 ± 10.1μg.ml^-1.day^-1. Volume of distribution at steady state (Vd_ss) was found to be 0.162 ± 0.017 ml.kg^-1. The overall elimination rate constant (K_el) and mean residential time (MRT) were calculated to be 0.017 ± 0.003 day^-1 and 59.1 ± 7.8 days, respectively. Based on mean serum levels of carbaryl, the elimination half life (t_1/2β) of carbaryl in buffalo calves was calculated to be 67.37 days. Carbaryl had a long half-life in in buffalo calves. This finding will serve as a guideline with regards to observation of meat withdrawal times in buffaloes exposed to carbaryl. This is very important since carbaryl is recommended for spraying over fodder crops to control pests. However further studies are needed to verify this by measuring actual tissue residue levels of carbaryl at regular time intervals after exposure.