Pharmacokinetics of praziquantel and pyrantel pamoate combination following oral administration in cats

Objectives The pharmacokinetics of praziquantel and pyrantel pamoate has never been reported in cats. The present study was designed to establish the plasma concentration-time profile and to derive pharmacokinetic data for a combined formulation of praziquantel and pyrantel in cats, after a single, oral administration. Methods Twenty-two clinically healthy adult cats were used, each receiving a single oral dose of praziquantel (8.5 mg/kg) and pyrantel (100 mg/kg). Blood samples were collected at regular time points up to 48 h post-dosing. Plasma concentrations of praziquantel and pyrantel were measured using a liquid chromatography-mass spectrometry-high-throughput screening method. Results Clinical examination of all cats did not reveal any side effects after oral administration of these medications. The terminal half-life for praziquantel and pyrantel was 1.07 and 1.36 h, respectively. Praziquantel peak concentration (C-max) was 1140 g/ml, reached at 1.22 h. The plasma concentrations of pyrantel after oral administration were low with a mean C-max of 0.11 g/ml, reached at a T-max of 1.91 h. Pyrantel showed a very limited absorption as pamoate salt, suggesting permanence and efficacy inside the gastrointestinal tract, where the adult stages of most parasitic nematodes reside. Conclusions and relevance Pyrantel showed a very limited absorption as pamoate salt. Praziquantel was rapidly absorbed following oral administration and the concentrations achieved suggest that praziquantel could be an effective and safe medication in cats. Although some resistance problems are arising as a result of their long use, these anthelminthic products can still play a major role in parasitic control, especially in geographical areas where the high cost of newer treatments or necessity of parenteral administration could decrease the number of treated animals.