Pharmacokinetics of new high-concentration and long-acting praziquantel oily suspensions after intramuscular administration in cattle.

The aim of the study was to develop praziquantel (PZQ) oily suspensions with 30% PZQ high concentration for intramuscular injection and investigate their pharmacokinetics in cattle. Two optimized formulations containing 30% PZQ were developed in this study, and their quality met the technical standards set by the Ministry of Agriculture of the People's Republic of China. After intramuscular administrations of the suspensions (30 mg/kg), no significant differences were observed between the two oily suspensions. However, compared with the market available PZQ tablet after oral administration (150 mg/kg), our injections revealed longer plasma elimination half-life (26.23, 22.16 h vs 6.35 h) and mean residence time (27.10, 25.88 h vs 9.16 h), indicating the antiparasitic efficacy of our suspensions may be prolonged, and further clinical efficacy investigation is needed. In addition, the relative bioavailability of our formulated suspensions was improved up to 441.32% and 425.60% compared with the oral reference product. Therefore, the injectable suspensions have the potential to become antiparasitic agents for the treatment of cattle schistosomiasis.