Chapter 41: Antimycobacterial Drugs for Treating Tuberculosis and Other Diseases

Antimycobacterial Drugs for Treating Tuberculosis and Other Diseases of pharmacology explores the specialized therapeutic strategies required to combat mycobacterial infections, which are characterized by their chronic nature, unique acid-fast cell wall structures, and ability to remain dormant within human tissue. The primary clinical focus is on managing Tuberculosis (TB), a significant global health threat caused by organisms that sequester within granulomas to evade host defenses and standard chemotherapy. Effective TB management necessitates a prolonged, multidrug approach typically involving a four-drug first-line regimen: isoniazid, rifampin, pyrazinamide, and ethambutol. Isoniazid is a cornerstone of therapy that disrupts mycolic acid synthesis but requires activation by the bacterial catalase-peroxidase enzyme. Its effectiveness and safety are notably influenced by genetic polymorphism, as individuals are categorized as either fast or slow acetylators, with the latter being more susceptible to drug-induced peripheral neuritis—a condition often mitigated by pyridoxine supplementation. Rifampin provides broad-spectrum activity by inhibiting bacterial RNA polymerase, though it is a potent inducer of cytochrome P450 enzymes, leading to numerous drug interactions and a characteristic reddish-orange discoloration of bodily secretions. Pyrazinamide is crucial for its ability to kill dormant bacilli in acidic environments, thereby shortening the necessary duration of treatment, while ethambutol targets cell wall formation but requires careful monitoring for dose-related optic neuritis and color blindness. To address the rise of multidrug-resistant (MDR-TB) and extensively drug-resistant (XDR-TB) strains, the chapter introduces newer agents like bedaquiline, which blocks the proton pump for ATP synthase, and pretomanid. Furthermore, the text details the treatment of leprosy (Hansen disease) using dapsone to inhibit folic acid synthesis and clofazimine for its anti-inflammatory and bactericidal properties, particularly in managing erythema nodosum leprosum. Finally, therapeutic protocols for Mycobacterium avium complex (MAC) are discussed, highlighting the role of macrolides like azithromycin and clarithromycin in treating immunocompromised patients. The overarching goal across all mycobacterial treatments is to ensure adherence through measures like Directly Observed Therapy (DOT) to prevent relapse and the further development of microbial resistance.