What it's for (Indications)
- Rifampicin and isoniazid (INH), as provided in fixed-dose combination products such as RIFINAH 450 mg, are specifically indicated for the treatment of all forms of active tuberculosis (TB) caused by susceptible strains of *Mycobacterium tuberculosis*.
- This combination is a fundamental component of standard first-line anti-tuberculosis chemotherapy regimens.
- It is utilized in both the intensive (initial) phase and the continuation phase of treatment, often in conjunction with other antituberculous agents like pyrazinamide and ethambutol, depending on the specific treatment protocol and national guidelines.
- The primary goal of this combination therapy is to achieve rapid bactericidal activity, prevent the emergence of drug resistance due to monotherapy, and ensure comprehensive eradication of mycobacterial infection in both pulmonary and various extrapulmonary manifestations of tuberculosis.
- The selection of this combination underscores its proven efficacy in controlling disease progression and achieving favorable patient outcomes.
Dosage Information
| Type | Guideline |
|---|---|
| Standard | N/A - Specific dosage and administration guidelines are not provided in the available data. Consult with a healthcare professional for appropriate dosing. |
Safety & Warnings
Common Side Effects
- Heartburn, nausea, vomiting, diarrhea, sore mouth, rash, muscular pain, pain in extremities, visual disturbances, pruritus (unpleasant sensation of skin), menstrual disturbances, fever, skin eruptions, and pyridoxine deficiency.
Serious Warnings
- Black Box Warning: SEVERE AND FATAL HEPATOTOXICITY: The use of rifampicin and isoniazid, particularly in a fixed-dose combination, is associated with a significant risk of severe and sometimes fatal hepatotoxicity. Isoniazid-induced hepatitis can occur at any time during therapy but is statistically more common in the first three months of treatment. The risk of developing severe hepatitis is dose-related and increases significantly with advanced age, in patients with pre-existing liver disease, with daily alcohol consumption, and in individuals who are genetically slow acetylators. Patients must be closely monitored for all signs and symptoms of liver injury (e.g., profound fatigue, unexplained weakness, malaise, anorexia, persistent nausea, vomiting, dark urine, jaundice, pale stools). Baseline liver function tests (LFTs) should be performed prior to initiating therapy, and monitoring should continue periodically or immediately if clinical signs and symptoms suggestive of liver damage occur. The drug combination must be immediately discontinued if objective evidence of progressive liver damage is detected. DRUG INTERACTIONS: Rifampicin is a potent inducer of multiple cytochrome P450 enzymes (e.g., CYP3A4, CYP2C9, CYP2C19, CYP2D6), which can significantly accelerate the metabolism of many co-administered drugs. This potent enzyme induction often leads to subtherapeutic plasma concentrations and potential therapeutic failure of the interacting medications. This interaction can be clinically significant and life-threatening for drugs with narrow therapeutic indices (e.g., certain antiretrovirals, oral contraceptives, anticoagulants, immunosuppressants, antiarrhythmics, corticosteroids, oral hypoglycemics). Careful consideration, dose adjustments, or the selection of alternative therapies are imperatively required. Patients must be thoroughly educated on all potential drug interactions and advised to report any new medications or supplements.
- Pregnancy: No definite data regarding pregnancy is available; therefore, use with caution and consult a doctor.
- Lactation: The effect of this medication is undetermined in lactating females; consult a doctor.
How it Works (Mechanism of Action)
The therapeutic efficacy of the rifampicin and isoniazid (INH) combination against *Mycobacterium tuberculosis* is derived from their distinct yet synergistic mechanisms of action. Rifampicin, a rifamycin antibiotic, exerts its potent bactericidal effect by inhibiting bacterial DNA-dependent RNA polymerase. It achieves this by binding specifically to the beta subunit of the bacterial enzyme, thereby preventing the initiation of RNA chain elongation. This blockade of transcription consequently inhibits bacterial RNA synthesis and subsequent protein synthesis, leading to bacterial cell death. Rifampicin demonstrates high selectivity for bacterial RNA polymerase, with minimal affinity for eukaryotic RNA polymerase, contributing to its selective toxicity. Isoniazid (INH), conversely, is a prodrug that requires enzymatic activation by the mycobacterial catalase-peroxidase enzyme (KatG). Once activated, the resulting isonicotinoyl radical forms adducts with NAD+ and NADP+, which in turn irreversibly inhibit several essential enzymes involved in mycolic acid biosynthesis. Key targets include enoyl-acyl carrier protein reductase (InhA) and beta-ketoacyl-ACP synthase (KasA). Mycolic acids are crucial components of the mycobacterial cell wall; their inhibition leads to the disruption of cell wall integrity and ultimately results in the bactericidal action of INH, particularly against rapidly multiplying bacilli. The combined action of these agents significantly enhances bactericidal activity and profoundly reduces the likelihood of *Mycobacterium tuberculosis* developing resistance.
Commercial Brands (Alternatives)
No other brands found for this formula.