Pharmacokinetics and dynamics of eliminating of active substance in medicinal preparation for veterinary use salmogir® in trout after external use

A mandatory requirement in the development of a medicinal product is the study of its pharmacokinetics and the dynamics of eliminating of active substance after using to target animal species. The pharmacokinetics of praziquantel and its active metabolite (trans-hydroxypraziquantel) were determined after a single administration of the preparation at a therapeutic dose of 0.1 ml/l (5 mg PZQ/l) with an exposure of 30 minutes. The maximum concentration of praziquantel in blood plasma (Cmax) was 3860 ng/ml, the time-to-peak concentration (Tmax) was 0.5 h, the elimination halflife of praziquantel from blood plasma (t1/2) was 54.9 h. The following results were obtained for trans-hydroxypraziquantel: Cmax – 64.5 ng/ml, Tmax – 1 h; t1/2β – 11.5 h. Praziquantel was detected in trout blood plasma in significant quantities for 48 hours after effect of a medicinal bath, and 120 hours in trace amounts (1-5 ng/ml). Trans-hydroxypraziquantel was detected in trout blood for for 48 hours after exposure to a praziquantel solution. Active substances in the blood plasma were determined according to the developed technique which had been validated. The study of praziquantel residue excretion was carried out after a single exposure to the drug in 30-minute baths at a dose of 20 mgPZQ/l (maximum dose). Withdrawal period for trout: 150 degree- days.