Abstract
The use of fixed dose combinations (FDCs) of anti-TB (Tuberculosis) drugs is recommended by World Health Organization (WHO) and International Union Against Tuberculosis and Lung Disease (IUATLD) to ensure proper treatment of tuberculosis. FDCs have the advantage of simplifying the prescription of drugs and the management of drug supply and may also limit the risk of drug resistant TB arising as a result of inappropriate drug selection and monotherapy. But the major problem with the use of FDCs is the poor/variable bioavailability of rifampicin. In the present work, the physical form of rifampicin in various marketed anti-TB formulations was identified with the help of solid-state characterization techniques. As rifampicin shows pH dependent solubility, dissolution studies of the same FDCs were conducted in three dissolution media having differing pH values. Results indicated that there was no correlation between the rifampicin polymorphic form present in the formulations and the drug release from the same. Powder dissolution and particle size analysis studies also indicated that the principle factor affecting dissolution of rifampicin form I and form II is the particle size and not the energy differences.