Commonly Used Anti-Tuberculosis Medications

Effective treatment of tuberculosis (TB) relies heavily on the use of oral anti-TB drugs that target and eliminate Mycobacterium tuberculosis, the bacterium responsible for the disease. These medications are typically classified into two main categories: first-line and second-line anti-tuberculosis drugs. The selection of appropriate medication depends on factors such as drug sensitivity, patient history, and whether the case is newly diagnosed or involves drug-resistant strains.

First-Line Anti-TB Drugs

First-line drugs are the cornerstone of TB treatment due to their high efficacy and favorable safety profile when used correctly. They are primarily prescribed for new, drug-sensitive cases of tuberculosis. The most commonly used first-line agents include:

Isoniazid (INH): A bactericidal agent that disrupts mycolic acid synthesis in the bacterial cell wall.
Rifampicin (RIF): Also bactericidal, it inhibits RNA polymerase, thereby preventing protein synthesis in the bacteria.
Pyrazinamide (PZA): Effective in acidic environments, such as inside macrophages, making it crucial during the initial phase of treatment.
Ethambutol (EMB): Bacteriostatic, it interferes with cell wall synthesis and is often used to prevent resistance.
Streptomycin (SM): An injectable aminoglycoside that targets protein synthesis; though less commonly used today due to toxicity concerns.

These medications are typically combined in the initial intensive phase of therapy to rapidly reduce bacterial load and prevent the emergence of resistant strains.

Second-Line Anti-TB Drugs

Second-line drugs come into play when patients develop resistance to first-line treatments—commonly seen in multidrug-resistant TB (MDR-TB) or extensively drug-resistant TB (XDR-TB). These medications are generally less effective, more toxic, and require longer treatment durations. Common second-line agents include:

Sodium para-aminosalicylate (PAS): An older antibiotic that inhibits folate synthesis in TB bacteria.
Prothionamide: A thioamide that disrupts mycolic acid production.
Amikacin and Kanamycin: Injectable aminoglycosides effective against resistant strains.
Capreomycin: A cyclic peptide antibiotic used in MDR-TB regimens.
Fluoroquinolones such as Ofloxacin and Moxifloxacin: Broad-spectrum antibiotics with strong activity against TB, especially moxifloxacin, which has become a key component in newer regimens.

Treatment with second-line drugs often lasts 18 to 24 months and requires close monitoring due to potential side effects like ototoxicity, nephrotoxicity, and psychiatric disturbances.

TB Treatment Principles and Phases

The standard approach to treating pulmonary tuberculosis follows five core principles: early diagnosis, regular dosing, full course completion, appropriate dosage, and combination therapy. This strategy helps maximize cure rates while minimizing the risk of drug resistance.

Two Phases of TB Therapy

Intensive Phase: Lasting 2–3 months, this stage uses multiple drugs (usually four) to aggressively kill actively replicating bacteria and reduce transmission risk.

Continuation (or Consolidation) Phase: This phase follows the intensive stage and lasts 4–7 months, focusing on eliminating dormant or slowly growing bacilli to prevent relapse.

Different Treatment Regimens Based on Case Type

Treatment plans vary depending on the type of TB:

Newly diagnosed, drug-sensitive TB: Typically treated with a 6-month regimen (2HRZE/4HR).
Retreatment of sputum-positive TB: May require an extended 8-month course with careful monitoring.
Drug-resistant TB: Requires individualized regimens based on drug susceptibility testing, often involving second-line drugs for up to two years.

Preventing Drug Resistance and Controlling Spread

To combat the growing threat of drug-resistant TB, the DOTS (Directly Observed Treatment, Short-course) strategy remains one of the most effective public health interventions. By ensuring patients take their medication under supervision, DOTS significantly improves adherence and cure rates.

Early detection of resistant cases is equally critical. Rapid molecular tests like GeneXpert MTB/RIF allow for timely identification of rifampicin resistance, enabling prompt initiation of appropriate therapy. Public health efforts must focus on strengthening diagnostic infrastructure, improving access to care, and reducing stigma associated with TB.

In conclusion, while several potent anti-tuberculosis drugs are available, their success hinges on proper use, patient compliance, and robust healthcare systems. Continued research, global cooperation, and investment in TB control programs are essential to achieving a TB-free future.