Comparative Pharmacokinetics and Bioequivalence of Pour-On Ivermectin Formulations in Korean Hanwoo Cattle

This study aimed to conduct a bioequivalence study of applying three pour-on ivermectin formulations at a dose of 1 mg/kg on the back of Korean native beef cattle (Hanwoo). To conduct bioequivalence testing, the pharmacokinetics of three groups (control Innovator, test Generic A, and test Generic B) of five clinically healthy Korean Hanwoo cattle (average weight 500 kg) were studied. After topical application to the skin, blood samples were drawn at the indicated times. These blood samples were analyzed using liquid chromatography-tandem mass spectrometry (LC-MS/MS). The time required to reach the maximum concentration (T_max), the maximum concentration (C_max), and the area under the curve (AUC_last) of each pharmacokinetic parameter were compared for bioequivalence. The results showed that the control had a T_max of 41 ± 1.24 h, a C_max of 0.11 ± 0.01 μg/mL, and an AUC_last of 9.33 ± 0 h*μg/mL). The comparator Generic A had a T_max of 40 ± 1.14 h, a C_max of 0.10 ± 0.01 (μg/mL, and an AUC_last of 9.41 ± 0.57 h*μg/mL, while Generic B had a T_max of 40 ± 2.21 h, a C_max of 0.10 ± 0.01 μg/mL, and an AUC_last of 9 h*μg/mL. The values of the bioequivalence indicators C_max, T_max, and AUC were all within the range of 80% to 120%, confirming that all three tested formulations were bioequivalent. In conclusion, the study showed that the two generic products were bioequivalent to the original product in Hanwoo cattle.