When Bedaquiline is Unavailable for Rifampicin-Resistant, Fluoroquinolone-Susceptible TB
Use a longer all-oral regimen containing a later-generation fluoroquinolone (levofloxacin or moxifloxacin), linezolid, clofazimine, cycloserine, and pyrazinamide for 15-21 months after culture conversion, with at least 5 drugs in the intensive phase and 4 in the continuation phase.
The Challenge
The 2025 ATS/CDC/ERS/IDSA guidelines strongly recommend the 6-month BPaLM regimen (bedaquiline, pretomanid, linezolid, moxifloxacin) as first-line treatment for rifampicin-resistant, fluoroquinolone-susceptible TB 1. However, when bedaquiline is unavailable, you must revert to longer conventional regimens based on the 2019 guidelines 2.
Recommended Regimen Components
Core Drugs (Strong/Conditional Recommendations)
Fluoroquinolone (MUST include):
- Levofloxacin OR moxifloxacin (strong recommendation) 2
- This is your most effective agent and forms the backbone of the regimen
Linezolid (strongly suggested):
- 600 mg daily (conditional recommendation) 2
- Second most effective agent after fluoroquinolones
- Monitor for peripheral neuropathy and myelosuppression
Clofazimine (suggested):
- Conditional recommendation 2
- Provides additional bactericidal activity
- Monitor for skin discoloration (reversible)
Cycloserine (suggested):
- Conditional recommendation 2
- Add pyridoxine 25-50 mg daily to prevent neuropsychiatric effects
- Monitor mental health closely
Pyrazinamide (suggested):
- Include when isolate not resistant to pyrazinamide 2
- Provides sterilizing activity
Supporting Evidence from Recent Research
A 2026 Chinese trial demonstrated that a 6-9 month all-oral regimen (levofloxacin, linezolid, cycloserine, clofazimine, pyrazinamide) achieved 76.1% favorable outcomes versus 63.7% with injectable-containing regimens 3. This validates the efficacy of fluoroquinolone-linezolid-based regimens when bedaquiline is unavailable.
Treatment Duration
Intensive Phase:
- 5-7 months after culture conversion 2
- Use at least 5 effective drugs
Continuation Phase:
- Continue until 15-21 months total after culture conversion 2
- Use at least 4 effective drugs
Total duration: 15-21 months after culture conversion
Drugs to AVOID
Do NOT include:
- Amoxicillin-clavulanate (strong recommendation against) 2
- Macrolides (azithromycin, clarithromycin) - strong recommendation against 2
- Ethionamide/prothionamide - avoid if more effective drugs available 2
Ethambutol:
- Only include when you cannot assemble 5 effective drugs without it 2
- It is the weakest agent in your arsenal
Critical Monitoring
Monthly throughout treatment:
- Sputum smear and culture 4
- Clinical symptoms and physical exam
- Liver function tests
- Complete blood count (for linezolid toxicity)
- Renal function
Additional monitoring:
- ECG at baseline and periodically (fluoroquinolones can prolong QT)
- Mental health assessment (cycloserine)
- Visual acuity if using ethambutol
- Hearing tests if considering aminoglycosides
Common Pitfalls
Insufficient drug count: Always start with at least 5 likely effective drugs in the intensive phase. Counting drugs the patient is resistant to leads to treatment failure.
Premature discontinuation: The full 15-21 months after culture conversion is critical. Stopping early dramatically increases relapse risk.
Ignoring drug susceptibility testing: Obtain baseline DST and repeat if cultures remain positive. Adjust regimen based on results 2.
Underestimating linezolid toxicity: Peripheral neuropathy and myelosuppression are common. Some experts reduce to 300 mg daily after 2-4 months, though this is not explicitly in guidelines.
Missing fluoroquinolone resistance: If fluoroquinolone resistance develops or is present, this entire approach fails. You would need to construct a different regimen entirely.
Alternative Consideration
The 2026 Chinese guidelines suggest a modified 9-month regimen (bedaquiline, linezolid, levofloxacin, clofazimine, cycloserine) when bedaquiline IS available but pretomanid is not 4. However, since your question specifies bedaquiline unavailability, this is not applicable.
The Reality
Without bedaquiline, you are using a significantly inferior regimen with longer duration, more toxicity, and lower success rates. The 2019 guidelines acknowledge "very low certainty in the evidence" for these longer regimens 2. Every effort should be made to access bedaquiline through compassionate use programs, international procurement, or patient transfer to facilities with access. The difference in outcomes is substantial enough to justify extraordinary measures to obtain it.