**4. Fixed-dose combination antituberculosis therapy**

The World Health Organisation and the International Union Against Tuberculosis and Lung Disease (IUATLD) endorsed FDC anti-TB therapy in 1994 [11]. Concerns were raised about proper bioavailability of the component medications following the release of this proposal and its more widespread application, particularly rifampicin (RIF) due to its accelerated breakdown in the presence of isoniazid (INH) [12, 13]. Despite the potential benefits of FDC anti-TB medicines, questions about their efficacy remain unanswered. Many observational studies and clinical trials have been done to determine the efficacy of FDC medications in preventing treatment failure, illness relapse, and drug resistance. The use of FDC medications has resulted in favourable [37], unfavourable [38], or no therapy outcomes in various investigations [39, 40]. Despite current conflicting findings, the WHO [41], the International Standards for Tuberculosis Care (Standard 8) [42], and the American Thoracic Society all endorse FDC formulations for active TB treatment [10, 43].
