Treatment Regimen for Patients with a History of Tuberculosis
For patients with a history of tuberculosis (TB), the recommended treatment approach depends on whether they have relapsed, failed prior treatment, or have completed treatment successfully in the past. 1
Relapse After Prior Treatment
Assessment of Relapse
- Obtain microbiological confirmation through sputum cultures
- Perform drug susceptibility testing on new isolates
- Evaluate adherence to previous treatment regimen
- Assess for risk factors for drug resistance
Treatment of Relapse
For patients previously treated with directly observed therapy (DOT) with drug-susceptible TB:
- Start standard four-drug regimen: isoniazid, rifampin, pyrazinamide, and ethambutol 2
- Adjust based on susceptibility test results when available
For patients with irregular prior treatment or without DOT:
- Higher risk of acquired drug resistance exists
- Begin expanded regimen with at least 5-6 drugs 2
- Include isoniazid, rifampin, pyrazinamide, ethambutol, a fluoroquinolone, and an injectable agent (streptomycin, amikacin, kanamycin, or capreomycin)
For patients with suspected exogenous reinfection:
- Base regimen on drug susceptibility pattern of presumed source case
- If source case has drug-susceptible TB, use standard four-drug regimen
- If source case has drug-resistant TB, use expanded regimen based on resistance profile
Treatment Failure
Definition and Approach
- Treatment failure: Continued or recurrent positive cultures after 4 months of treatment with confirmed medication adherence 2
- NEVER ADD A SINGLE DRUG TO A FAILING REGIMEN 2
- Assume drug-resistant organisms until proven otherwise
Management of Treatment Failure
- Obtain specimens for culture and drug susceptibility testing
- Begin new regimen with at least 3 drugs not previously used
- Include at least 5 effective drugs in the intensive phase and 4 drugs in the continuation phase 1
- Consult with experts in treating drug-resistant TB
Standard Treatment for New TB Cases
Initial Phase (First 2 Months)
- Daily isoniazid, rifampin, pyrazinamide, and ethambutol 1, 3, 4
- Ethambutol may be omitted if local isoniazid resistance is <4% 1
Continuation Phase (Next 4 Months)
- Daily isoniazid and rifampin for 4 months 1, 4
- Total treatment duration: 6 months for drug-susceptible pulmonary TB
Special Considerations
HIV Co-infection
- Extend treatment to 9 months and at least 6 months after sputum conversion 2, 1
- If CD4 count <100/μL, use daily or three times weekly isoniazid and rifampin in continuation phase 1
Extrapulmonary TB
- Most forms can be treated with standard 6-month regimen 1
- Exceptions:
Drug-Resistant TB
- Multidrug-resistant TB (MDR-TB): 15-21 months after culture conversion 1
- Pre-XDR-TB and XDR-TB: 15-24 months after culture conversion 1
- Treatment should be managed by specialists experienced in drug-resistant TB 2, 1
Monitoring and Follow-up
- Monthly clinical evaluations during treatment 1
- Sputum cultures at 2 months and end of treatment 1
- Monitor for adverse effects:
- Baseline and regular liver function tests
- Visual acuity and color discrimination testing if on ethambutol
- Pyridoxine (vitamin B6, 25-50 mg/day) with isoniazid to prevent neuropathy 1
Key Pitfalls to Avoid
- Adding a single drug to a failing regimen (creates resistance to the new drug) 2
- Inadequate initial regimen in areas with high drug resistance 1
- Failure to ensure adherence (main reason for treatment failure) 2, 1
- Delayed recognition of treatment failure (reevaluate if smear-positive at 3 months) 2, 1
- Inadequate monitoring for adverse effects, especially hepatotoxicity 1
Remember that directly observed therapy (DOT) is strongly recommended to ensure adherence and prevent the development of drug resistance 2, 1.