Determination of bioequivalence of lomefloxacin tablets using urinary excretion data

The present study describes development of a sensitive and simple HPTLC method for estimation of lomefloxacin (LMF) in human urine. The drug was extracted using chloroform after adjusting the pH of urine to 7.0. Chloroform extract was spotted on silica gel 60 F(254) TLC plate and was developed in a mixture of n-butanol-methanol-ethyl acetate-6 M ammonia (4:2:3:2, v/v/v/v) as the mobile phase and scanned at 290 nm. The peak for LMF resolved at R(F) of 0.40+/-0.02. The method was validated in terms of linearity (50-600 microgram/ml), precision, specificity and accuracy. The limit of detection and limit of quantification for LMF in urine were found to be 20 and 50 microgram/ml, respectively. The average recovery of LMF from urine was 91.93%. The proposed method was applied to generate urinary excretion data for LMF after administration of two market LMF tablet formulations (400 mg, Formulation R and Formulation T) to six healthy human volunteers in a two-treatment, open, crossover design. Various pharmacokinetic parameters like peak excretion rate ((dAU/dt)(max)), time for peak excretion rate (t(max)), AUC(0-48), AUC(0- infinity ), cumulative amount and % cumulative amount of LMF excreted, elimination half-life (t(1/2)), terminal elimination rate constant (k(el)) and overall elimination rate constant (K), were calculated for both the formulations. The average cumulative amounts of LMF excreted in urine after administration of Formulation R and Formulation T were found to be 321.60 mg (80.40% of dose) and 296.51 mg (74.13% of dose), respectively. The urinary excretion profiles of LMF upto 48 h for both the formulations were found to be similar. Statistical comparison (90% confidence intervals of ratio) of various pharmacokinetic parameters of Formulation T with that of Formulation R revealed that Formulation T is bioequivalent with Formulation R.