Pharmacokinetics of (-)-clausenamide and its major metabolite 6-hydroxyl-clausenamide in Beagle dogs by HPLC/MS

AimTo establish a sensitive and accurate method to study the pharmacokinetics of (-)-clausenamide ［(-)-clau］ and its major metabolite 6-hydroxyl-clausenamide (6-OH-clau) in the plasma of the Beagle dog. Methods(-)-Clau was orally administered to six Beagle dogs at the dose of 30 mg·kg^-1, venous blood from front leg was sampled and plasma was separated for analysis. After extraction with ethyl acetate, the plasma samples were analyzed by HPLC/MS and the mobile phase was a mixture of methanol-water-acetic acid (60∶40∶0.8) at the flow rate of 1.0 mL·min^-1. The API-ES positive ion SIM detection was carried out for the detection of both (-)-clau (［M+H］⁺, m/z 298) and 6-OH-clau (［M+H-H₂O］⁺, m/z 296) with glipzide (glip) (［M+H］⁺, m/z 446) as internal standard. The pharmacokinetic parameters were calculated by 3P97 software. ResultsThere was good linear relationship (r>0.999) between the SIM responses and the concentrations for (-)-clau and 6-OH-clau at the range from 1.0 to 200 ng·mL^-1 and 0.2 to 40.0 ng·mL^-1, respectively. The absolute recovery was greater than 85%. The plasma concentration-time curves of (-)-clau and 6-OH-clau were both best fitted to a two-compartment model. The C_max of (-)-clau and 6-OH-clau were (21±10) ng·mL^-1 and (3.9±2.2) ng·mL^-1, T_max were (0.8±0.5) h and (1.3±0.5) h, T_1/2α were (0.9±0.6) h and (1.4±0.6) h, T_1/2β were (19±23) h and (13±12) h, AUC_{0-24 h} were (69±14) h·ng·mL^-1 and (12±7) h·ng·mL^-1 respectively. ConclusionThe established HPLC/MS method was sensitive and specific for the determination of (-)-clau. It was shown that the absorption and first phase elimination of (-)-clau were very quick in Beagle dogs, but the terminal elimination was very slow. The plasma concentration profile of its major metabolite 6-OH-clau was similar to (-)-clau and the AUC was relatively small in comparison with (-)-clau.