Sex-related plasma disposition of ivermectin following pour-on administration in goats

The effect of sex difference on the pharmacokinetic profiles of ivermectin (IVM) was investigated following pour-on administration in goats. A total of 12 (six males and six females) Kilis goats were allocated into two treatment groups with respect to sex. The pour-on formulation of IVM was administered topically (pour-on) at dose rate of 0.5 mg/kg bodyweight. Blood samples were collected at various times between 1 h and 40 days after treatment and the plasma samples were analysed by high-performance liquid chromatography (HPLC) using fluorescence detection. Substantial sex-related differences on the plasma disposition of IVM were observed between males and female goats following pour-on administration. The last detectable plasma concentration of IVM was significantly later in males (16.17 days) compared with female animals (10.67 days). There were no significant differences on Cmax, tmax and the area under the concentration-time curve-AUC values between male and female groups, respectively. However the terminal half-life (t1/2λz) and mean plasma residence time (MRT) in male goats (2.35 days and 4.78 days, respectively) were significantly longer compared with female animals (1.42 days and 3.55 days, respectively) and this suggesting that the excretion patterns of IVM in male and female animals are probably different each other.