Comparative study of bioavailability of closantel bolus and suspension dosage forms in sheep

Bioavailability study is a scientific and practical method to evaluate and compare the quality of different pharmaceutical products. The aim of this study was to compare the pharmacokinetic parameters obtained from bioavailability study of suspension and bolus formulations of closantel in sheep. Twenty eight lambs, 6 to 8 months old weighing around 50 kg, were randomly divided into two groups. Each sheep in the first group received 500 mg bolus of closantel and in the second group received 10 mg/kg suspension of closantel. Blood samples were taken at 0, 4, 8, 12, 16, 20, 24, 32, 48 and 72 hours after administration of the drugs and then the concentration of closantel in plasma was measured by an HPLC method using fluorescence detector. To compare the bioavailability of two dosage forms, different pharmacokinetic parameters including Cmax, Tmax and AUC were calculated by Drug Kinetics software and then analyzed with t-student and F tests. Pharmacokinetic parameters for suspension were AUC = 2931±648.2, C max = 62.21±7.74, Tmax = 23.14±4.2 and for bolus they were AUC = 2049.1±421.2, C max = 56.38±14.28, Tmax = 22.93±1.83. While there was significant difference between AUC of closantel suspension and bolus formulations, we did not find significant differences between C max and Tmax of suspension and bolus dosage forms. It seems that two dosage forms of closantel may show different bioavailability in some animals such as sheep.