Pharmacokinetics and bioavailability of R-phencynonate in Beagle dogs

Objective To evaluate the pharmacokinetics(PK)properties and bioavailability of R-phencynonate(L-8021)in Beagle dogs.Methods Fifteen healthy Beagle dogs were randomly divided into three groups,each group was orally given single dose of 0.1 mg·kg-1,0.4 mg·kg-1 and 1.2 mg·kg-1 R-phencynonate respectively.After one week cleaning,the middle dose group was injected 0.4 mg·kg-1 dose.Blood samples(about 2 mL)were collected in heparinized tubes before dosing and at 0.033,0.083,0.25,0.5,0.75,1,2,4,6,8,12 h after administration,and were then immediately centrifuged at 2000 g for 15 min.The pharmacokinetics(PK)properties and bioavailability of the drugs was evaluated using the liquid chromatographic-tandem mass spectrometric(LC-MS/MS)method.Results After p.o.administration of 0.1,0.4 and 1.2 mg·kg-1 R-phencynonate,tmax ranged within 0.65-1.2 h;t1/2z ranged within 2.84-3.36 h;CLz/F ranged within 5.00-9.32 L·h-1·kg-1;Cmax ranged within 1.87-70.34 ng·mL-1;AUC(0-t)ranged within 9.80-250.12 μg·L-1·h;After i.v.administration of 0.4 mg·kg-1,t1/2z was 2.52 h;AUC(0-t)was 238.11 μg·L-1·h.Conclusions L-8021 was dose-dependent within the range of 0.1-1.2 mg·kg-1 in Beagle dogs and the blood drug concentration-time curves were all best fitted to first order absorption two-compartment open model after via po administration of three different dosages.Following oral administration to Beagle dogs,the absolute bioavailability of L-8021 was 17.82%,which was very low and resulted from poor absorption.