Entrapment of multiple anti‐Tb drugs in microemulsion system: Quantitative analysis,stability, and in vitro release studies

The use of multiple drug regimes for the treatment of tuberculosis is restricted because of the degradation of Rifampicin in the presence of Isoniazid. In the present report, the microemulsion comprising Tween 80/ethanol/oleic acid/Buffer (pH 7.4) has been investigated for encapsulating Rifampicin (RIF), Isoniazid (INH), and Pyrazinamide (PZA) in different combinations. The main idea is to use the compartment of different domains of microemulsion for encapsulating drugs of different solubilties. The structural changes in the microstructure of microemulsion have been investigated in the light of the changes occurring in the presence of ATDs (anti‐Tb drugs) in binary or ternary mixtures through conductivity and viscosity. Optical microscopy and ¹H NMR helped in estimating the shape and location of ATDs in microemulsion system. Electronic spectroscopy has been utilized qualitatively and quantitatively for understanding the stability and release of RIF from the composed formulation with various binary or ternary mixtures. Dissolution and release kinetics have been carried out to get an idea on the release of drugs from microemulsion formulation. ATDs in single and mixed drug formulations followed non‐Fickian release behavior except for RIF in pH 7.4 release medium. The investigations employed have given us a fair success to predict not only the stability but also the release mechanism of ATDs in single and mixed drug formulations. © 2009 Wiley‐Liss, Inc. and the American Pharmacists Association J Pharm Sci 99: 1896–1911, 2010