A review on recent advances in the stability study of anti-mycobacterial drugs

Several factors, including characteristic polymer composition of the cell wall, based on peptidoglycans cross-linked with arabinogalactans, together with the lipid layer contribute to the high resistance of Mycobacterium tuberculosis to antibiotics and other anti-tuberculosis drugs, leading to the development of new treatment methods. Implementation of therapeutic drug monitoring for anti-mycobacterial drugs in routine clinical practice requires understanding of the limited stability of these drugs. Rifampicin and isoniazid are the main anti-tuberculosis drugs that generate degradation products during sample handling and storage. Therefore, analytical methods used for analysis of clinical samples collected from tuberculosis patients treated with a combination of different drugs should enable the separation of the studied analytes from their metabolites and degradation products. Moreover, the samples require strictly regulated collection and storage conditions to prevent degradation processes. The purpose of this review was to present recent data on the stability studies of anti-mycobacterial drugs, specifically used as first-line treatment in patients with tuberculosis. Detailed degradation pathway of rifampicin was described, including conditions influencing the formation of specific rifampicin related substances. Moreover, the results of the stability studies of anti-mycobacterial drugs were presented in various matrices in conditions determined by international guidance such as U.S. Food and Drug Administration (FDA) or International Council for Harmonisation (ICH) guidelines. Particular attention was given to analytical methods designed for analysis of anti-mycobacterial drugs in the presence of their degradation products. Finally, recommendations proposed by different authors for collection, processing and storage of clinical samples to increase stability of anti-mycobacterial drugs were summarized.