ABSTRACT:
This work aims to the development of a liquid chromatography-tandem mass spectrometry (LC-MS/MS) method for measuring ciprofloxacin (CIP) in rabbits serum following intra-gastric dosing and application of the developed method for pharmacokinetic studies of CIP released from six generic and one reference products. A positive electrospray tandem mass spectrometry coupled with liquid chromatography was used. Chromatographic analysis was done using of XTerra® RP C8 column and a mobile phase of acetonitrile/water/formic acid (80:20:0.025v/v/v). A simple protein precipitation method using acetonitrile was used for cleaning up the serum samples before LC/MS/MS analysis. Quantification was achieved using multiple reaction monitoring (MRM) at m/z 332.7>245.5 (CIP) and m/z 364.7>263.2 (rufloxacin, internal standard). The pharmacokinetics of the absorbed CIP fractions from the examined brands were calculated using PK-software for non-compartmental pharmacokinetics data analysis. The developed LC-MS/MS method showed a good linearity (r= 0.99), precision (RSD%<6.1%) and accuracy (Bias%<8.5%)over the CIP concentration range 0.5-6µg/ml in rabbits serum. Stability studies indicated that CIP serum samples were stable for at least 4 month sat -35oC.The calculated pharmacokinetic parameters were in the ranges: Cmax 1.1-6.0 µg/ml, Tmax 0.5-1.0 hr , AUC0-t5.3-16.0 µg.hr/ml and the % relative bioavailability was from 35.6 to 77.5%. The developed LC-MS/MS method was successful for measuring CIP levels in rabbits serum following intra-gastric dosing. The proposed route of drug administration permits an accurate drug placement and collection of serum samples. Pharmacokinetic studies revealed some differences of the absorption patterns of the generic and reference products which reflects variation of the antibacterial efficacy among CIP brands.