What is the recommended treatment after exposure to tuberculosis (TB)?

Recommended Treatment After Exposure to Tuberculosis

After exposure to tuberculosis (TB), treatment with isoniazid for 9 months is recommended for most individuals with latent TB infection (LTBI), while alternative regimens include rifampin for 4 months or rifampin plus pyrazinamide for 2 months depending on specific patient factors and suspected drug resistance patterns. 1

Initial Assessment After TB Exposure

Before initiating treatment, it's essential to:

1. Rule out active TB disease through:

   • History and physical examination
   • Chest radiography
   • Bacteriologic studies when indicated 1

2. Determine infection status:

   • Tuberculin skin test (TST) using the Mantoux method with 5 TU purified protein derivative
   • A TST reaction ≥5 mm is considered positive in HIV-infected persons 1
   • For general population, ≥10 mm is considered positive 1

Treatment Regimens for Latent TB Infection

First-line Regimens:

1. Isoniazid (INH):

   • 9 months daily or twice weekly (preferred for most patients)
   • Dosage: Adults - 300 mg daily; Children - 10-15 mg/kg daily (not exceeding 300 mg)
   • Twice-weekly dosing should only be given as directly observed therapy (DOT) 1
   • Pyridoxine (vitamin B6) should be added for persons at risk of neuropathy 1

2. Rifampin:

   • 4 months daily
   • Dosage: Adults - 10 mg/kg daily (not exceeding 600 mg); Children - 10-20 mg/kg daily (not exceeding 600 mg) 2
   • Particularly useful for patients who cannot tolerate isoniazid or pyrazinamide 1
   • Also recommended for contacts of patients with isoniazid-resistant, rifampin-susceptible TB 1

3. Rifampin plus Pyrazinamide:

   • 2 months daily
   • Particularly effective for HIV-infected persons 1
   • Should be administered as DOT due to potential hepatotoxicity 1
   • Note: Due to reports of severe liver injury, regimens without pyrazinamide may be preferred when treatment completion can be ensured 1

Special Populations

HIV-infected Persons:

• When using isoniazid, 9 months rather than 6 months is recommended 1
• All HIV-infected persons with positive TST (≥5 mm) should receive treatment for LTBI 1
• Close contacts of infectious TB patients should be treated regardless of TST results 1

Pregnant Women:

• For HIV-negative pregnant women, isoniazid for 9 or 6 months is recommended
• For women at high risk of progression (HIV-infected or recently infected), treatment should not be delayed due to pregnancy 1
• For women at lower risk, some experts recommend waiting until after delivery 1

Children and Adolescents:

• Isoniazid for 9 months (daily or twice weekly) is the recommended regimen 1

Contacts of Drug-Resistant TB:

1. Isoniazid-resistant TB contacts:

   • Rifampin and pyrazinamide daily for 2 months
   • If pyrazinamide intolerance, rifampin daily for 4 months 1

2. Multidrug-resistant TB contacts (resistant to both isoniazid and rifampin):

   • Pyrazinamide and ethambutol OR pyrazinamide and a fluoroquinolone (levofloxacin or ofloxacin) for 6-12 months
   • Immunocompetent contacts: treat for at least 6 months or observe
   • Immunocompromised contacts: treat for 12 months 1
   • Expert consultation should be sought 1

Monitoring During Treatment

Clinical Monitoring:

• Initial clinical evaluation before starting treatment
• Follow-up evaluations:
  • Monthly for isoniazid or rifampin alone
  • At 2,4, and 8 weeks for rifampin plus pyrazinamide 1
• Patients should be educated about side effects and advised to stop treatment and seek medical evaluation if they occur

Laboratory Monitoring:

• Baseline testing not routinely indicated for all patients
• Recommended for:
  • Patients with suspected liver disorders
  • HIV-infected persons
  • Pregnant women and women in immediate postpartum period
  • Persons with history of chronic liver disease
  • Regular alcohol users 1

Common Pitfalls and Caveats

1. Failure to rule out active TB: Always exclude active TB before starting LTBI treatment to avoid inadequate treatment and development of drug resistance 1

2. Drug interactions: Rifampin can induce metabolism of many medications including HIV protease inhibitors. In such cases, rifabutin may be substituted 1

3. Hepatotoxicity: Monitor for signs of liver damage, especially with isoniazid and pyrazinamide. Some experts recommend withholding isoniazid if transaminase levels exceed 3 times the upper limit of normal with symptoms or 5 times without symptoms 1

4. Poor adherence: Consider DOT for intermittent regimens and for populations at risk of non-adherence 1

5. BCG vaccination: History of BCG vaccination should not influence the decision to treat LTBI 1

By following these evidence-based recommendations, clinicians can effectively manage TB exposure and prevent progression to active disease, significantly contributing to TB control efforts.