Trial of High-Dose Rifampin in Patients With TB

This is a Phase II, multi-site, dose-ranging trial comparing 3 doses of RIF in a multidrug regimen for treatment of smear-positive, pulmonary TB. The intervention phase of this prospective, randomized, double-blinded trial will last 8 weeks, the duration of the standard "intensive" phase for short-course chemotherapy for TB. During that time, subjects will receive the following companion drugs: isoniazid (INH, 5 mg/kg/day), ethambutol (EMB, 20 mg/kg/day), and pyrazinamide (PZA, 25 mg/kg/day), pyridoxine (50 mg), the standard doses used in treatment. Subjects will also be randomized to receive one of the following weight-based doses of the study drug, rifampin (RIF): 10 mg/kg/day (standard dose, control), 15 mg/kg/day (intervention 1), 20 mg/kg/day (intervention 2). All patients will receive at least standard dose of RIF, the efficacy of which in multidrug-treatment for TB is well established. Placebo will be used to control only the additional RIF capsules provided in the intervention arms. Subjects, clinicians, and laboratory staff will be blinded to study arm. All patients in the same weight band will receive the same total number of tablets (fixed-dose combination plus RIF and/or placebo). Blinding is essential to reduce the probability of biased reporting of adverse events.

After randomization, other covariates that may result in heterogeneity within strata (e.g., presence of cavitation, HIV serostatus), will be adjusted for in analyses. It is important to maintain the ability to measure the effect (if any) of these potential characteristics on treatment outcome. If we were to stratify on these characteristics, we could not estimate their confounding (or interaction) effect. All doses will be delivered orally and fully supervised. All patients will receive weight-based doses of fixed-dose combinations according to package inserts. This will be supplemented by active RIF capsules or placebos, or both, according to weight and treatment arm. They will also all receive 50 mg of pyridoxine to prevent peripheral neuropathy, a common side effect of INH.

Inclusion criteria

• Newly diagnosed pulmonary TB with acid-fast bacilli (>=2+) in a stained sputum smear, ultimately confirmed by culture.
• Susceptibility of isolate to INH and RIF by HAIN test.
• Willingness to undergo HIV testing according to the National Health Guidelines for TB control in Peru. The study will also consider patients who have had negative HIV serostatus documented within six months prior to enrollment or if verifiable positive serostatus was documented using a validated test any time previously.
• Age >/= 18 years and <61 years.
• Signed informed consent.
• Negative serum pregnancy test (women of childbearing potential).
• Women with child-bearing potential must agree to practice a double-barrier method of birth control during treatment. Adequate contraceptives (condoms and spermicide) will be provided by the study to avoid pregnancy among female subjects.
• Karnofsky score of at least 50 (requires considerable assistance and frequent medical care).
• Intends to remain in jurisdiction of health center during study and follow up.

Exclusion criteria

• Body weight <30 kg.
• Prior treatment with multidrug anti-TB therapy for more than one month.
• Resistance on HAIN to INH and/or RIF. These patients will be treated according to local programmatic guidelines.
• Central nervous system or miliary TB.
• Clinical or radiological signs suggestive of pericardial or pleural involvement.
• Presence of significant hemoptysis. Patients who cough up frank blood (more than blood-streaked sputum) will not be eligible for enrollment.
• Known intolerance to any of the study drugs; use of concomitant drugs that interfere with the pharmacokinetics of anti-TB drugs; use of concomitant hepatotoxic drugs (other than companion study drugs) for which potential drug interactions or synergistic toxicity are known: boosted protease inhibitors, non-nucleoside reverse transcriptase inhibitors, azole antifungals and statins; use of antibiotics that are contraindicated during the study's TB therapy; current daily use of acetaminophen or paracetamol for two weeks or more.
• History of liver disease.
• Uncontrolled condition that might interfere with drug absorption, distribution, metabolism or excretion (i.e. chronic gastrointestinal disease, renal insufficiency defined by creatinine clearance <60mL/min).
• Uncontrolled diabetes mellitus (HbA1c>7.5%).
• Refusal to be tested for HIV infection; HIV infection with contraindication for treatment with efavirenz (including resistance).
• Pulmonary silicosis.
• Breastfeeding.
• Rifampin contraindications such as hypersensitivity or jaundice.
• Likely difficulty adhering to the protocol, as assessed by the investigator.
• Laboratory results in the 14 days preceding enrollment showing:

• Serum amino alanine transferase (ALT) >2 times upper limit of normal
• Serum total bilirubin concentration >2.5 times upper limit of normal
• Serum creatinine concentration > 2 times upper limit of normal and/or creatinine clearance <60 mL/min
• Hemoglobin concentration < 7.0 g/dL
• Platelet count < 150,000/mm3
• White blood count <4500 cells/μL.
• Having a serological test positive for HBVsAg (hepatitis B virus surface antigen) or for HCVAb (hepatitis C virus antibody)test.