Bioavailability studies are used to define the effect of changes in the physicochemical properties of the drug substance and the effect of the drug product on the pharmacokinetics of the drug. Bioequivalence studies are used to compare the bioavailability of the same drug from various drug products. Bioavailability and bioequivalence can also be considered as performance measures of the drug product in-vivo. If the drug products are bioequivalent and therapeutically equivalent, then the clinical efficacy and the safety profile of these drug products are assumed to be similar and may be substituted for each other. If we ensure maximum bioavailability of a brand with a minimum production cost, it will be benefited for the patients in every aspect. So, comparative Bioavailabolity studies of various brands should be performed to establish a dosage regiment demonstrating evidence of safety and efficacy.