Determination of Bioequivalence of Two Oral Formulations of Gatifloxacin Tablets in Healthy Male Volunteers Using Urinary Excretion Data

The present study describes development of a sensitive and simple HPTLC method for estimation of gatifloxacin (GTN) in human urine sample. The drug was extracted using chloroform after adjusting the pH of urine to 7.0. Chloroform extract was spotted on silica gel 60 F254 TLC plate and was developed in a mixture of n-butanol /methanol/ammonia (5:1:2, v/v/v) as the mobile phase and scanned at 292 nm. The peak for GTN resolved at RF of 0.47. The method was validated in terms of linearity (200 to 1200 ng/μL), precision, specificity and accuracy. The limit of detection and limit of quantification for GTN in urine were found to be 25.64 and 77.70 ng, respectively. The average recovery of GTN from urine was 100.68%. The proposed method was applied to generate urinary excretion data for GTN after administration of two market GTN tablet formulations (400 mg, Formulation R and Formulation T) to twelve healthy human volunteers in a two- treatment, open, crossover design. Various pharmacokinetic parameters like peak excretion rate ((dXU/dt)_max), time for peak excretion rate (t_max), AUC_0-48, AUC_0-∞, cumulative amount and % cumulative amount of GTN 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 GTN excreted in urine after administration of Formulation R and Formulation T were found to be 304 ± 11mg (82.32 ± 2.75 % of dose) and 315.2 ± 13.50 mg (78.8 ± 3.37 % of dose), respectively. The urinary excretion profiles of GTN up to 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.Bioequivalence.