Rifampicin

Indications

Rifampicin is used for: Tuberculosis, Leprosy, Brucellosis, Meningitis , Legionnaire's disease; Staphylococcal infections

Adult Dose

Oral Tuberculosis Adult: 10 mg/kg/day or 2-3 times/wk. Max: 600 mg/day. <50 kg: 450 mg daily; >50 kg: 600 mg daily. Leprosy 600 mg once mthly. Prophylaxis against meningococcal meningitis 600 mg twice daily for 2 days. Prophylaxis against meningitis due to Haemophilus influenzae 600 mg/day for 4 days. Hepatic impairment: Max: 8 mg/kg/day.

Child Dose

Oral Tuberculosis 10–20 mg/kg, max 600 mg for TB q24h With directly observed biweekly therapy, dosage is still 10–20 mg/kg/dose (max 600 mg) twice weekly 20 mg/kg/day for 2 days for meningococcus prophylaxis, q12h

Renal Dose

Administration

Should be taken on an empty stomach. Best taken on an empty stomach 1 hr before or 2 hr after meals.

Contra Indications

Hypersensitivity to rifampicin or other rifamycins. Patient w/ jaundice. Concurrent use w/ saquinavir/ritonavir therapy.

Precautions

Patient w/ history of alcoholism. Hepatic and renal impairment. Elderly, malnourished patients, childn <2 yr. Pregnancy and lactation. Patient Counselling May permanently stain soft contact lenses. Monitoring Parameters Monitor liver function (AST, ALT, bilirubin), CBC, mental status, sputum culture; chest x-ray 2-3 mth into treatment.

Pregnancy-Lactation

Interactions

May accelerate the metabolism and reduce the effect of drugs that are metabolised by CYP450 enzymes (e.g. quinidine, phenytoin, theophylline). Decreased concentrations of atovaquone and increased concentrations of rifampicin when taken concomitantly. Concurrent use of ketoconazole and rifampicin may result in decreased serum concentrations of both drugs. May decrease serum concentrations of enalaprilat. Reduced absorption by antacids. Increased risk of hepatotoxicity w/ halothane or isoniazid. Potentially Fatal: Increased potential for hepatotoxicity when taken concomitantly w/ saquinavir/ritonavir combination.

Adverse Effects

Side effects of Rifampicin : Facial flushing and itching, w/ or w/o a rash, flu-like syndrome characterised by episodes of fever, chills, headache, dizziness, bone pain, shortness of breath, and malaise; GI adverse effects (e.g. nausea, vomiting, anorexia, diarrhoea, epigastric distress), pseudomembranous colitis, eosinophilia, leucopenia, haemolytic anaemia; alterations in kidney function and renal failure, menstrual disturbances, oedema, myopathy, muscular weakness; orange-red discolouration of the urine, faeces, sweat, saliva, sputum, tears, and other body fluids; Rarely, eye irritation and visual disturbances, anaphylaxis or shock. Potentially Fatal: Hepatotoxicity, hypotension, sinus tachycardia, ventricular arrhythmias, seizures and cardiac arrest, thrombocytopenia and purpura.

Mechanism of Action

Rifampicin suppresses initiation of chain formation for RNA synthesis in susceptible bacteria by binding to the beta subunit of DNA-dependent RNA polymerase, thus blocking RNA transcription.