Comparison Of Pharmacokinetics And Bioavailability Of Prednisone Acetate And Prednisone In Beagle Dogs

Background Prednisone acetate is an ester prodrug,which can be rapidly hydrolyzed in vivo to prednisone,and further metabolized in the liver by11-β-hydroxysteroid dehydrogenase to form the active product prednisolone.Prednisone is a common glucocorticoid drug,has anti-inflammatory,antiallergic and immunosuppressive effects.As oral preparations,prednisone tablets are used abroad,while prednisone acetate tablets are used in China.There is no report in the literature on the comparison of the pharmacokinetics and bioavailability between prednisone acetate and prednisone.Objective After an oral administration of 2.0 mg·kg^-1 prednisone acetate and1.8 mg·kg^-1prednisone by a randomized,two-way crossover in Beagle dogs,we planned to compare pharmacokinetics and bioavailability of prednisone acetate and prednisone in Beagle dogs,and to provide a basis for the design of clinical experiments.Method To improve the stability of prednisone acetate in plasma,the degradation prednisone acetate was investigated,and eventually found condition to keep the plasma sample stable.Dexamethasone was used as internal standard（IS）.After a protein precipitation using acetonitrile as the precipitation solvent,the analytes and IS were separated on a HSS T₃（2.1×50 mm,1.8μm）via gradient elution with mobile phase consisting of methanol-5 mmol·L^-1 ammonium acetate containing 0.1%formic acid.The MS/MS detection was performed in multiple reaction monitoring mode（MRM）.The product ions used for quantitative analysis of m/z 401.2→295.2 for prednisone acetate,m/z 359.2→313.2 for prednisone,m/z 361.2→325.1 for prednisolone and m/z 393.2→373.0 for dexamethasone（IS）.This animal experiment was conducted in the Experimental Animal Center of Shanghai Institute of Medicine,Chinese Academy of Sciences.Results In validation of the bioanalytical method,the linear calibration curves for prednisone acetate,prednisone and prednisolone were obtained in the concentration range of 1.00 to 1000 ng·m L^-1,2.00 to 2000 ng·m L^-1 and 2.00 to2000 ng·m L^-1 in dog plasma.With treatment of 10%formic acid aqueous solution（plasma sample contain of1%formic acid）,stability of prednisone acetate,prednisone and prednisolone in dog plasma were evaluated after stored at room temperature for 24 h,after four freeze-thaw cycles,and after stored at-20℃ and-70℃ for 27 days.The post-preparation stability was measured after exposure of the processed samples at room temperature and 4℃ for 24 h.Under the above storage conditions,the plasma samples were found stable.The results showed that the concentration of prednisone acetate in all dog plasma samples was below the quantitation limit of 1.00 ng·m L^-1,which indicated that prednisone acetate was hydrolyzed rapidly during absorption.After an oral dose of prednisone acetate and prednisone,the C_max and the AUC_0-t of prednisone was2.6-fold and 1.4-fold higher in the former than in the latter,respectively.At same time,the C_max and the AUC_0-t of prednisolone was 2.8-fold and 1.8-fold higher in the former than in the latter.By calculating the AUC_0-t ratio of prednisolone,the relative bioavailability of prednisone acetate to prednisone was only（57.1±10.5）%.Conclusion The methods was developed and applied in the simultaneous determination of prednisone acetate,prednisone,and active metabolite prednisolone in dog plasma.It was suitable for the pharmacokinetic study of prednisone acetate and prednisone in Beagle dogs.A comparative study on the pharmacokinetic and bioavailability of prednisone acetate and prednisone in Beagle dogs was conducted.The results showed that the plasma concentrations of prednisone and prednisolone after an prednisone acetate oral dose were significantly lower than those after a prednisone oral dose,and the pharmacokinetic parameters of the two were significantly different.