Antitubercular Drugs: Treatment Regimens and DOTS Strategy

Posted on May 21, 2026 in Medicine & Health

Antitubercular Drugs: Treatment and Classification

Antitubercular drugs are medications used to treat tuberculosis (TB) caused by Mycobacterium tuberculosis. These drugs are categorized into first-line and second-line treatments.

First-Line Antitubercular Drugs

First-line drugs are the most effective and are routinely used for all new TB cases. They include:

  • Isoniazid (H)
  • Rifampicin (R)
  • Pyrazinamide (Z)
  • Ethambutol (E)
  • Streptomycin (S)

Second-Line Antitubercular Drugs

Second-line drugs are utilized for multidrug-resistant TB (MDR-TB). These include levofloxacin, moxifloxacin, amikacin, kanamycin, cycloserine, ethionamide, para-aminosalicylic acid, linezolid, bedaquiline, and delamanid.

Adverse Effects of First-Line Medications

First-line drugs are associated with specific side effects:

  • Isoniazid: Causes peripheral neuropathy due to pyridoxine deficiency; vitamin B6 is administered concurrently.
  • Rifampicin: Causes orange-red discoloration of urine, tears, and saliva; it is also a potent enzyme inducer.
  • Pyrazinamide: Associated with hyperuricemia and joint pain.
  • Ethambutol: Causes optic neuritis, leading to blurred vision and red-green color blindness.
  • Streptomycin: Causes ototoxicity, particularly damage to the vestibular apparatus, resulting in vertigo and hearing loss.

The DOTS Treatment Strategy

The standard treatment strategy for tuberculosis is DOTS (Directly Observed Treatment, Short-course). Recommended by the World Health Organization, this strategy ensures patients take medication under the supervision of a health worker, significantly reducing treatment failure and drug resistance.

Phases of Tuberculosis Treatment

TB treatment is divided into two distinct phases:

  • Intensive Phase (2 months): Utilizes four drugs (HRZE) to rapidly kill actively multiplying bacilli and render the patient non-infectious.
  • Continuation Phase (4 months): Utilizes two drugs (HR) to eliminate dormant bacilli and prevent relapse.

The standard short-course chemotherapy for a new TB patient is 2HRZE followed by 4HR.

Historical RNTCP Regimen Categories

Under the classical RNTCP framework, treatment was categorized as follows:

  • Category I: New sputum-positive pulmonary TB and severe extrapulmonary TB (2HRZE / 4HR).
  • Category II: Relapse, treatment after default, and treatment failure cases (2HRZES + 1HRZE / 5HRE).
  • Category III: New sputum-negative pulmonary TB and less severe extrapulmonary TB (2HRZ / 4HR).
  • Category IV: Multidrug-resistant TB treated with second-line drugs based on susceptibility testing.

In summary, antitubercular drugs are administered in combination to prevent resistance and ensure a complete cure, utilizing the DOTS framework to maintain patient compliance.