A rapid, sensitive and selective HPLC method for the determination of levofloxacin in rat plasma is developed and validated. Separation is done on a Phenomenex C18 RP column with a mobile phase of acetonitrile – 0.4 % triethylamine (pH 3.1) in the ratio of 18:82 % v/v and detection at 295 nm. The standard curve is linear (r > 0.998) over the concentration range of 20.0–5000 ng/ml. The lower limit of quantification (LOD) for levofloxacin is 10.0 ng/ml. The maximum concentration (Cmax) obtained for two brands Levoflox and Generic formulation are 132.72 and 113.97 ng/ml respectively. The half life (t1/2) of levofloxacin for Levoflox and Generic are calculated as 1.763 and 1.628 h. Area under the curve AUC.t 0 of Levoflox and Generic is calculated as 271.18 and 279.84 ng h/ml and ¥ t AUC is calculated to be 4.31 and 10.97 ng h/ml respectively and ¥ 0 AUC is calculated to be 275.48 and 290.81 ng h/ml. Elimination rate constant (kel) is calculated for Levoflox and Generic from the slope of log concentration versus time curve with regression analysis. Elimination rate constant is found to be 0.393 and 0.4272 h-1. This study shows that there is no significant difference in kinetic parameters between two products. So the two formulations are considered to be bioequivalent.
