Physicochemical and Bioequivalence Studies on Some Brands of Levofloxacin Tablets Registered in Nigeria

Aims: This study was aimed at comparing the physicochemical and bioavailability profiles of some brands of Levofloxacin 500mg tablets that are registered in Nigeria by her regulatory authority and to examine the feasibility of interchangeability of the brands.
Methodology: The physicochemical equivalence of ten brands of Levofloxacin 500 mg tablets (LEV-1 to LEV-10) were evaluated using both official and unofficial standards including weight variation, hardness, friability test, chemical assay, disintegration, dissolution rate and drug content. Five of the brands were also evaluated for bioavailability profiles using a single dose randomized two period cross–over designs measuring the concentration of drugs in the urine. Urinary samples before dosing and at various appropriate time intervals up to 12 hours were analyzed by validated Double Beam U. V. Spectrophotometer method with 99.8% extraction recovery. Pharmacokinetic parameters for bioequivalence evaluation Cmax, Tmax and AUC were determined.
Results: The resultsshowed that 60% of the levofloxacin brands (LEV-2, LEV-4, LEV-5, LEV-7, LEV-8 and LEV-9) failed in at least one of the tested physicochemical parameters. The statistical comparison of the physicochemical parameters showed no difference between the innovator brand (LEV-1) and three of the tested generic brands (LEV-3, LEV-6 and LEV-10). Unlike LEV-5, the results obtained from the reference ratios of the parameters from bioavailability studies for the physicochemical equivalent brands were found to be within bioequivalence acceptable range with the reference brand indicating that they are bioequivalent in terms of Cmax and AUC to the innovator brand.
Conclusion: The study indicates that 60% of the brands may not be used interchangeably with the innovator brand; consequently, the therapeutic substitution of these brands is not advisable. The formulation and/or the manufacturing process affect the weight uniformity, content uniformity, dissolution and thus the bioavailability of the drug products.