Why Drug-Resistant TB Is So Hard to Treat

A Global Health Problem

Tuberculosis is caused by Mycobacterium tuberculosis and remains one of the world's leading infectious causes of death. Drug-resistant forms, including multidrug-resistant TB (MDR-TB) and extensively drug-resistant TB (XDR-TB), are harder to cure and can take much longer to treat.

Long, Toxic Treatment

Older regimens for drug-resistant TB often lasted 18 to 24 months and involved injectable drugs, which carried significant toxicity and made adherence difficult. Many patients experienced severe side effects or did not complete treatment.

Why a Shorter Oral Option Matters

A regimen that is all-oral and lasts six months can reduce the burden on patients, lower the chance of treatment failure from missed doses, and make care more feasible in many settings.

Key Takeaways

• Pretomanid received FDA approval on August 14, 2019, as part of the BPaL regimen for adults with pulmonary XDR-TB or treatment-intolerant or non-responsive MDR-TB.
• Pretomanid must be used only in combination with bedaquiline and linezolid. It is not approved as a standalone drug.
• The regimen is 26 weeks long, with pretomanid 200 mg once daily, bedaquiline 400 mg once daily for two weeks followed by 200 mg three times weekly, and linezolid usually 600 mg once daily.
• In the Nix-TB trial, 95 of the first 107 patients achieved a successful outcome.
• The label warns about liver reactions, myelosuppression, peripheral and optic neuropathy, lactic acidosis, and cardiac rhythm abnormalities.
• Patients require close monitoring and dose adjustment of linezolid when side effects occur.

What Is Pretomanid

Origin

Pretomanid was developed by TB Alliance, a nonprofit organization focused on tuberculosis drug development. It is the first tuberculosis drug developed and registered by a nonprofit organization, according to TB Alliance.

Chemical Class

Pretomanid belongs to the nitroimidazooxazine class of compounds. This is a newer chemical class in the context of TB drugs and is among the few new antituberculosis agents approved in recent decades.

Dosage Form

Pretomanid is supplied as 200 mg oral tablets. Patients with swallowing difficulty may have special instructions, which the prescribing information describes.

FDA Approval: August 14, 2019

The Decision

The FDA approved pretomanid on August 14, 2019, as part of a combination regimen with bedaquiline and linezolid. The approved population is adults with pulmonary extensively drug-resistant TB, or multidrug-resistant TB that is treatment-intolerant or non-responsive.

Significance

TB Alliance described pretomanid as only the third new anti-TB drug approved by the FDA in more than 40 years, which underscores how rarely new TB drugs reach the market.

Stewardship Language

The label states that pretomanid must be administered only as part of the combination regimen. This protects the effectiveness of all three drugs, since using any one alone can lead to resistance.

The Limited Population Pathway

What LPAD Is

Pretomanid was approved under the Limited Population Pathway for Antibacterial and Antifungal Drugs (LPAD). This pathway is intended for serious infections in small populations with few alternatives.

What It Means for Patients

The label is narrow, and the evidence base is smaller than for drugs approved in large populations. Clinicians weigh this evidence against the seriousness of drug-resistant TB and the lack of better options.

Ongoing Evidence

Additional studies, including trials of linezolid dosing in the BPaL regimen, continue to refine how the regimen is used.

What Is the BPaL Regimen

Three Drugs

BPaL combines bedaquiline, pretomanid, and linezolid. Each drug targets the tuberculosis bacterium through a different mechanism, which helps reduce the chance of resistance developing during treatment.

Duration

The labeled duration is 26 weeks. Clinicians can extend treatment if needed, but the regimen is designed as a six-month course.

Oral Administration

All three drugs are given by mouth. The label recommends taking pretomanid, bedaquiline, and linezolid with food, which helps absorption.

How Pretomanid Works

Activity Against Mycobacteria

Pretomanid is active against both actively growing and dormant Mycobacterium tuberculosis. It interferes with the bacterium's ability to produce components of its cell envelope and to generate energy, although the exact details are part of the drug's pharmacology described in the label.

Why Combination Matters

Using pretomanid with bedaquiline and linezolid aims to kill the bacteria more effectively and to prevent resistance to any one drug from undermining treatment.

Limits

Laboratory activity does not guarantee clinical cure. Treatment success depends on susceptibility, adherence, the extent of disease, and the patient's overall health.

Which Infections It Targets

Labeled Indication

The label covers pulmonary TB caused by susceptible Mycobacterium tuberculosis in adults with XDR-TB, or MDR-TB that is treatment-intolerant or non-responsive.

Not Approved For

The FDA approval does not cover drug-susceptible TB, latent TB infection, or extrapulmonary TB as labeled indications. These are managed under separate guidance.

Susceptibility Testing

Laboratory testing confirms drug susceptibility before and during treatment. Results determine whether the regimen is appropriate and guide adjustments.

Approved Use and Labeling Limits

Who Is Eligible

The labeled population is adults with pulmonary XDR-TB or treatment-intolerant or non-responsive MDR-TB.

Combination Requirement

Pretomanid must be given with bedaquiline and linezolid. It should not be given alone or with other drugs not specified in the regimen without specialist direction.

Pediatric Use

The labeled population is adults. Use in children requires specialist judgment outside the labeled indication.

The Nix-TB Trial: Design

Overview

Nix-TB was a phase 3 study conducted at three sites in South Africa. It evaluated the BPaL regimen in people with highly drug-resistant TB, including XDR-TB and treatment-intolerant or non-responsive MDR-TB.

Population

The trial enrolled 109 people. The study was designed to assess whether a six-month all-oral regimen could produce favorable outcomes in patients with limited options.

Outcome Measure

Favorable outcomes were assessed at six months after the end of treatment, reflecting whether the disease remained controlled without relapse.

The Nix-TB Trial: Results

Successful Outcomes

TB Alliance reported that 95 of the first 107 patients achieved a successful outcome after six months of treatment and six months of post-treatment follow-up. The FDA's summary reported a favorable outcome in 89 percent of patients.

Adverse Reactions

The trial reported hepatotoxicity, myelosuppression, and peripheral and optic neuropathy in association with the combination. These are the warnings reflected in the label.

Sputum Conversion

Patients typically converted to negative sputum cultures relatively quickly in the trial, which is an important early marker of treatment response.

Reading the Results Carefully

Small Trial

Nix-TB enrolled 109 patients at three sites. Small trials have wide uncertainty, and results may not apply equally to every population.

Favorable Outcome Definition

Favorable outcome includes cure without relapse at follow-up, so it is a composite outcome. Patients who did not reach that status were counted as unfavorable.

Real-World Data

Post-approval experience in the United States has been reported in small case series. Continued monitoring is important as use expands.

Dosing and Administration

Pretomanid

The labeled pretomanid dose is 200 mg taken orally once daily for 26 weeks.

Bedaquiline

The labeled bedaquiline schedule is 400 mg once daily for two weeks, followed by 200 mg three times weekly, with at least 48 hours between doses, for a total of 26 weeks. An alternative schedule of 200 mg daily for eight weeks followed by 100 mg daily for 18 weeks is also in the label.

Linezolid

The preferred linezolid dose is 600 mg once daily for 26 weeks. An alternative of 1,200 mg once daily is also labeled. Dose changes are based on side effects.

Food

The label recommends taking pretomanid, bedaquiline, and linezolid with food. Your team will confirm instructions for your prescription.

Missed Doses

Missed doses should be reported to the TB team promptly. Do not double up on your own, because the regimen is designed to be taken consistently.

Linezolid Dosing Choices and Adjustments

Why Linezolid Is Adjusted

Linezolid causes myelosuppression, peripheral neuropathy, and optic neuropathy, particularly with higher doses and longer exposure. The label allows dose reduction when these develop.

Stepwise Adjustment

If myelosuppression, peripheral neuropathy, or optic neuropathy occurs, the label directs reducing linezolid to 600 mg once daily, then to 300 mg once daily, or interrupting linezolid, as necessary.

Clinical Decisions

Your TB team makes these decisions based on symptoms, laboratory results, and the overall response to treatment.

Liver Reactions Warning

What Can Happen

Hepatic adverse reactions were reported with the combination regimen. Liver enzyme elevations and, in rare cases, more serious liver injury can occur.

Warning Signs

Report yellowing of the skin or eyes, dark urine, pale stools, abdominal pain, nausea, unusual tiredness, or itching.

Monitoring

Liver function is checked before and during treatment, with more frequent testing when risk is higher. Your team may stop or adjust therapy if liver injury develops.

Blood Count Warning

What Can Happen

Myelosuppression can cause anemia, low white blood cell counts, and low platelet counts. The label notes that anemia can be life-threatening in some cases.

Warning Signs

Report unusual bruising or bleeding, fever, sore throat, infections, or marked tiredness or shortness of breath.

Monitoring

Complete blood counts are monitored during treatment, and linezolid is reduced or interrupted if counts fall.

Peripheral and Optic Neuropathy Warning

Peripheral Neuropathy

Numbness, tingling, burning, or weakness in the hands or feet can occur. Peripheral neuropathy is among the most common adverse reactions with the regimen.

Optic Neuropathy

Changes in vision, including blurred vision, reduced color perception, or visual field loss, can occur. Report any vision change promptly, because vision testing is part of monitoring.

Why It Matters

Nerve and vision damage may not fully reverse. Early reporting allows the TB team to reduce linezolid before lasting damage occurs.

Lactic Acidosis Warning

What It Is

Lactic acidosis is a buildup of acid in the blood. The label notes that it was reported with the combination, and linezolid is a known cause.

Warning Signs

Report rapid or deep breathing, persistent nausea or vomiting, abdominal pain, unusual weakness, or confusion.

Management

Lactic acidosis can be serious. The team may adjust or stop linezolid and bedaquiline based on the severity.

Heart Rhythm Warning

Cardiac Rhythm Abnormalities

The label lists cardiac rhythm abnormalities among serious adverse reactions. Bedaquiline is associated with QT prolongation, so heart rhythm monitoring is part of safe use.

Warning Signs

Report palpitations, fainting, chest discomfort, or unusual shortness of breath.

Medication Review

Your team checks other medicines that can affect heart rhythm, because combining them increases risk.

Monitoring During Treatment

Baseline Testing

Before starting, the team typically checks liver function, blood counts, kidney function, vision, nerve function, electrolytes, and an electrocardiogram. Drug susceptibility testing is also essential.

During Treatment

Regular blood tests, symptom reviews, and vision and nerve assessments help detect problems early. Sputum cultures track treatment response.

After Treatment

Follow-up continues after the course ends to confirm lasting cure, because relapse can occur.

Common Side Effects

Most Frequent Effects

Peripheral neuropathy, anemia, nausea, and headache are among the more common adverse reactions. Many can be managed by adjusting linezolid.

Gastrointestinal Effects

Nausea, vomiting, and loss of appetite can occur. Taking the medicines with food may help.

Other Reactions

Joint pain, rash, and changes in taste have been reported with TB regimens. Tell your team about any new symptom.

Who Should Not Receive Pretomanid

Known Hypersensitivity

People with a known allergy to pretomanid or any component should not take it without specialist review.

Drug-Susceptible or Non-Resistant TB

The BPaL regimen is not used for drug-susceptible TB, where standard first-line treatment applies.

Other Conditions

People with significant liver disease, existing nerve or vision problems, heart rhythm disorders, or low blood counts need specialist evaluation before treatment.

Drug Interactions

Serotonergic Drugs

Linezolid can interact with serotonergic medicines, including some antidepressants, and may cause serotonin syndrome. The team will review your medications before treatment.

Medicines That Affect Heart Rhythm

Bedaquiline can prolong the QT interval. Combining it with other drugs that affect heart rhythm requires careful review.

Other Medications

Give your team a complete list of medications, including prescriptions, over-the-counter products, and supplements. Antacids and some supplements can affect absorption of TB medicines, so timing matters.

How BPaL Compares With Older Treatment

Older Regimens

Older regimens for drug-resistant TB often lasted 18 to 24 months and included injectable drugs. These carried significant toxicity and made adherence harder.

BPaL Advantages

BPaL is all-oral, six months long, and avoids injectables. This can reduce treatment burden and support better adherence.

BPaL Trade-Offs

The regimen still causes significant toxicity, including neuropathy, myelosuppression, and liver effects, so it requires close monitoring.

Public Health and Stewardship

Protecting New Drugs

New TB drugs are valuable only if they remain effective. Using the complete combination and completing the full course help prevent resistance.

Infection Control

Drug-resistant TB spreads through the air. Public health authorities and treatment teams manage infection control, including isolation when needed.

Reporting

TB is notifiable in most places. Public health teams track cases and support patients through treatment.

Availability and Cost

Access

Pretomanid is obtained through specialized TB treatment programs and specialty pharmacies. Public health programs may provide medicines at no cost, depending on location.

Cost

Costs vary widely by country and program. Ask your TB team or public health office about support options.

Coverage

Coverage and program support depend on the setting. Your team can help with paperwork and access.

Pregnancy, Breastfeeding, and Children

Pregnancy

TB treatment in pregnancy requires specialist planning. Decisions about the BPaL regimen should involve obstetric and TB specialists, weighing benefits against risks.

Breastfeeding

Discuss breastfeeding with your team before treatment, since infant exposure and monitoring should be considered.

Children

The labeled population is adults. Use in children is outside the labeled indication and requires specialist judgment.

Questions to Ask Your TB Team

• Is my TB confirmed as XDR-TB or treatment-intolerant or non-responsive MDR-TB?
• What is my complete regimen, and how will the doses be adjusted?
• What tests will be done before and during treatment?
• What symptoms should make me call you right away?
• How will I be followed after treatment ends?

Frequently Asked Questions

Q: What is pretomanid used for?

A: It is approved as part of the BPaL regimen for adults with pulmonary extensively drug-resistant TB, or multidrug-resistant TB that is treatment-intolerant or non-responsive.

Q: When was it approved?

A: The FDA approved it on August 14, 2019.

Q: Can I take pretomanid alone?

A: No. It must be taken with bedaquiline and linezolid.

Q: How long is treatment?

A: The labeled course is 26 weeks, unless your team decides to extend it.

Q: What are the main risks?

A: Liver reactions, low blood counts, nerve and vision damage, lactic acidosis, and heart rhythm changes. Your team monitors for these during treatment.

Q: Is it used for latent TB?

A: No. The approval is for highly drug-resistant pulmonary TB in adults. Other TB situations follow different guidance.

Q: What should I report right away?

A: Yellow skin or eyes, unusual bleeding, numbness, vision changes, fainting, or rapid breathing should be reported immediately.

Medical Disclaimer

This article is for general education only and does not provide medical advice, diagnosis, or treatment. Tuberculosis requires evaluation and management by qualified TB specialists and public health teams. Do not start, stop, or change any TB medicine without guidance from your care team. For dosing, warnings, and interactions, consult the current U.S. prescribing information on DailyMed. If you have chest pain, coughing up blood, severe breathing difficulty, yellow skin or eyes, fainting, or confusion, seek emergency care immediately.

Sources and Further Reading

• U.S. FDA approval of pretomanid (NDA 212862), August 14, 2019
• Pretomanid U.S. Prescribing Information, including the combination dosing, linezolid adjustment, and Warnings and Precautions sections (hepatic adverse reactions, myelosuppression, peripheral and optic neuropathy, lactic acidosis, and cardiac rhythm abnormalities)
• TB Alliance press release on FDA approval, August 14, 2019
• Conradie F, et al. Treatment of highly drug-resistant pulmonary tuberculosis (Nix-TB trial), New England Journal of Medicine, 2020
• CDC Emerging Infectious Diseases article on the 6-month BPaL regimen in the United States, January 2021
• World Health Organization guidelines on treatment of drug-resistant tuberculosis, including BPaL and BPaLM

This article reflects information available as of October 2026. Confirm current prescribing details with your healthcare provider and the latest FDA labeling. For more on MyOnlineMedShop, visit our blog or contact us.