Antituberculosis medications

Antituberculosis Medications

Antituberculosis medications are a class of drugs used to treat infections caused by the bacterium *Mycobacterium tuberculosis*, the causative agent of tuberculosis (TB). These medications are critical in the management and eradication of TB, a disease that primarily affects the lungs but can also impact other parts of the body.

Overview

Tuberculosis is a major global health concern, and effective treatment is essential to control its spread. The standard treatment regimen for TB involves a combination of several antituberculosis drugs, taken over a period of at least six months. This approach is necessary to prevent the development of drug-resistant strains of the bacterium.

First-line Antituberculosis Medications

The first-line drugs are the most effective and least toxic, forming the core of the standard treatment regimen. These include:

• Isoniazid (INH): A bactericidal agent that inhibits the synthesis of mycolic acids, essential components of the mycobacterial cell wall.
• Rifampicin (RIF): A broad-spectrum antibiotic that inhibits RNA synthesis by binding to the bacterial DNA-dependent RNA polymerase.
• Ethambutol (EMB): A bacteriostatic agent that interferes with the synthesis of the mycobacterial cell wall by inhibiting arabinosyl transferases.
• Pyrazinamide (PZA): A prodrug that is converted to its active form, pyrazinoic acid, in the acidic environment of the macrophage phagolysosome, where it disrupts mycobacterial cell membrane metabolism and transport functions.

Second-line Antituberculosis Medications

Second-line drugs are used when resistance to first-line drugs is present or when patients cannot tolerate first-line drugs. These include:

• Fluoroquinolones: Such as levofloxacin and moxifloxacin, which inhibit bacterial DNA gyrase and topoisomerase IV.
• Injectable agents: Such as amikacin, kanamycin, and capreomycin, which inhibit protein synthesis.
• Other agents: Such as ethionamide, cycloserine, and para-aminosalicylic acid, which have various mechanisms of action.

Drug Resistance

Drug-resistant TB is a significant challenge in TB control. Multidrug-resistant TB (MDR-TB) is resistant to at least isoniazid and rifampicin, while extensively drug-resistant TB (XDR-TB) is resistant to isoniazid, rifampicin, any fluoroquinolone, and at least one of the second-line injectable drugs.

Treatment Regimens

The standard treatment regimen for drug-susceptible TB involves an initial intensive phase of two months with isoniazid, rifampicin, pyrazinamide, and ethambutol, followed by a continuation phase of four months with isoniazid and rifampicin. Treatment regimens for drug-resistant TB are longer and more complex, often requiring the use of second-line drugs.

Side Effects

Antituberculosis medications can cause a range of side effects, from mild to severe. Common side effects include hepatotoxicity, peripheral neuropathy, and gastrointestinal disturbances. Monitoring and managing these side effects is an important aspect of TB treatment.

Also see

• Tuberculosis
• Drug resistance
• Infectious diseases
• Antibiotics