Kafosid (Rifampicin) Dosing
The recommended dose of rifampicin for tuberculosis treatment in adults is 10 mg/kg daily (maximum 600 mg) given as a single daily dose, or 10 mg/kg (maximum 600 mg) when given twice weekly or three times weekly as part of directly observed therapy. 1
Standard Dosing Regimens
Daily Therapy
- Adults: 10 mg/kg daily with a maximum dose of 600 mg 1
- Children: 10-20 mg/kg daily with a maximum dose of 600 mg 1
- Rifampicin should preferably be taken on an empty stomach, though it may be administered with food in patients with gastrointestinal intolerance 1
Intermittent Therapy (Directly Observed)
- Twice weekly: 10 mg/kg (maximum 600 mg) 1
- Three times weekly: 10 mg/kg (maximum 600 mg) 1
- All intermittent dosing regimens should be administered under directly observed therapy (DOT) 1
Special Populations
HIV-Infected Patients
- Standard dose: 600 mg daily for tuberculosis prophylaxis (4 months duration) 1
- Important caveat: Rifampin should usually not be coadministered with protease inhibitors and should not be coadministered with non-nucleoside reverse transcriptase inhibitors except for efavirenz 1
- Rifabutin can be substituted for rifampin when drug interactions are problematic, though rifabutin is contraindicated with ritonavir, hard-gel saquinavir, and delavirdine 1
Pediatric Dosing
- Daily: 10-20 mg/kg (maximum 600 mg) 1
- Twice weekly: 10-20 mg/kg (maximum 600 mg) 1
- Pediatric doses should not exceed normal adult doses 1
Renal Impairment
- No specific dose adjustment is typically required for rifampicin in renal impairment, as it is primarily eliminated through biliary excretion 2
- However, in patients with combined hepatic and renal dysfunction, elimination may be slower 2
Pharmacokinetic Considerations
Absorption and Distribution
- Peak serum concentrations of approximately 10 μg/mL occur 2 hours after a 600 mg oral dose 2
- The half-life is approximately 2.5 hours with a 600 mg dose 2
- Approximately 80% of rifampicin is protein-bound, mainly to albumin 2
Dose-Dependent Kinetics
- Critical point: With doses of 300-450 mg, the hepatic excretory capacity becomes saturated, resulting in more than proportional increases in serum concentrations with higher doses 2
- On repeated administration, autoinduction of metabolism occurs, increasing the rate of drug elimination and reducing half-life 2
Intravenous Administration
- Usual daily dose: 450-600 mg administered by IV bolus or IV drip infusion 3
- IV formulation is reserved for critically ill or comatose patients, or those with gastrointestinal absorption problems 3
- Treatment duration ranged from 1-113 days in clinical experience 3
Common Pitfalls and Monitoring
Drug Interactions
- Rifampicin has multiple potential drug interactions due to its potent induction of hepatic enzymes 1
- Particular attention must be paid to antiretroviral therapy compatibility 1
Adverse Effects
- May cause reddish to brown-orange discoloration of urine, feces, saliva, sweat, skin, and tears (can discolor soft contact lenses) 1
- Rifampicin competes with bilirubin for biliary excretion, potentially causing transient and reversible increases in bilirubin retention 2
- Hepatotoxicity is dose-related and requires monitoring 1