ABSTRACT
To assess the bioavailability of norfloxacin from urinary excretion relative to plasma concentration. Twelve healthy volunteers [22-33 years] participated in the study. Each received a previously developed [M], a local [L] and a multinational [Noroxin] tablet [Ref], 400 mg each, according to a random balanced three-way crossover design on 3 different days. Blood samples were collected over a 12-hour period and urine over a 24-hour period. Norfloxacin concentrations were analyzed by a validated HPLC method. An initial estimate of bioequivalence of the three products was obtained using analysis of variance on transformed data and based on confidence interval calculation. Elimination pharmacokinetic parameters [half-life and renal clearance] calculated from plasma concentration and urinary excretion data [mean values, n = 36] were comparable to reported values for norfloxacin. Interproduct differences in elimination parameters [mean values, n = 12] were statistically insignificant [F values, ANOVA]. Strong association was found between the mean of plasma concentration and urinary excretion rates for many volunteers [F values, regression analysis]. Relative bioavailability values calculated for the local and previously developed products relative to Noroxin were higher than 85% based on area under the curve and urinary excretion. Bioequivalence could not be established among the three tested products based on calculated 90% confidence intervals. Urinary excretion of norfloxacin may be a useful noninvasive tool for bioavailability assessment of norfloxacin oral formulations