RESUMO
Aim TodevelopandvalidateaLC-MS/MS assay to quantify halometasone in rabbit plasma and study pharmacokinetics of halometasone after dermal topical administration of Halometasone Cream.Meth-ods Theplasmasamplewassubmittedtoliquid-liquid extraction using methyl tertiary butyl ether,with dexa-methasone as the internal standard (IS ).Chromato-graphic separations were performed on a Diamonsil C18 column(100 mm ×4. 6 mm,5 μm)with a linear gra-dient of methanol and 2 mmol · L-1 ammonium ace-tate.Halometasone and dexamethasone(IS)were ion-ized with an ESI source operated in negative ion mode, and the detected ions were m/z 503. 1→413. 0 (halo-metasone),m/z 391. 0→361. 0 (dexamethasone ). The test article could be monitored in rabbit plasma when following single dermal topical administration of Halometasone Cream at 1 g/100 cm2 to rabbits by u-singavalidatedLC-MS/MSassay.Results Calibra-tion curve was linear over the concentration range of0. 02~20 μg·L-1 in rabbit plasma.For low,medi-um,high concentration of QC solutions,the intra-and inter-day precision was in the range of 3. 72% ~7. 87%, and the accuracy was within 99. 1% to 103%. The pharmacokinetic parameters in rabbits were as follows:Tmax,Cmax,AUC0-t,T1/2 was (7. 38 ± 1. 06)h,(1. 16 ±0. 527)μg·L-1,(18. 8 ±7. 23)h·μg·L-1 ,(13. 8 ±3. 70)h,respectively.Conclusions ThisLC-MS/MSanalysismethodhashighsensitivi-ty,and sample processing method is simple,which has been rigorously validated.The method could be suc-cessfully applied to the pharmacokinetic study of halo-metasone after skin administration of Halometasone Cream to rabbits.