Pharmacokinetics of a novel spot-on formulation of praziquantel for dogs.

Praziquantel (PZQ) is an anthelmintic drug used both in humans and animals that can be administered through various routes. There are transdermal formulations for cats, but only oral or subcutaneous dosage forms for dogs. Given the fact that the cat's skin and the dog's skin have different characteristics, which in turn affect bioavailability, we developed a PZQ spot-on formulation for dogs. This study was aimed at determining the plasmatic behavior of topically administered PZQ (Labyes(®)) in adult dogs. Dogs were administered PZQ (14.5mg/kg PZQ, from a solution of 100mg/ml). Blood samples were drawn before treatment onset and at the following time points after PZQ administration: 1, 2, 4, 6, 12, 24 and 48h. PZQ plasma concentration was determined by ultra-high performance liquid chromatography (UPLC) coupled to tandem mass spectrometry (MS/MS). Observed maximum concentration (Cmax), area under the concentration-time curve from the time of drug administration to infinity (AUCinf) and time to maximum concentration (Tmax) were calculated for each animal, and mean±SD for each parameter was obtained. Results were as follows: Cmax=56.0±15ng/ml; AUCinf=910.2±220ng*h/ml, Tmax=5.0±1.1h. This is the first study to provide pharmacokinetic data of a praziquantel spot-on formulation for dogs.