Dosing and uses of Rifadin, Rimactane (rifampin)
Adult dosage forms and strengths
capsule
- 150mg
- 300mg
injectable powder
- 600mg
Tuberculosis
10 mg/kg/day PO or 10 mg/kg PO twice weekly (directly observed therapy [DOT]); not to exceed 600 mg/day
Dosing considerations
- May be given in conjunction with isoniazid or with isoniazid and pyrazinamide
- Rifampin dosage not to exceed 600 mg/day
Neisseria Meningitidis Carrier
600 mg q12hr for 2 days
Haemophilus Influenzae Type B Infection
Prophylaxis
600 mg/day PO/IV for 4 days
Pediatric dosage forms and strengths
capsule
- 150mg
- 300mg
injectable powder
- 600mg
Tuberculosis
10-20 mg/kg/day IV/PO or 10-20 mg/kg PO twice weekly (DOT); not to exceed 600 mg/day
Neisseria Meningitidis Infection
Prophylaxis
≤1 month: 10 mg/kg/day PO divided q12hr for 2 days
>1 month: 20 mg/kg/day PO divided q12hr for 2 days; not to exceed 600 mg/day
Haemophilus Influenzae Type B Infection (Off-label)
Prophylaxis
≤1 month: 10 mg/kg/day PO for 4 days
>1 month: 20 mg/kg/day PO for 4 days; not to exceed 600 mg/day
Rifadin, Rimactane (rifampin) adverse (side) effects
1-10%
Elevated liver function test (LFT) results (up to 14%)
Rash (1-5%)
Epigastric distress (1-2%)
Anorexia (1-2%)
Nausea (1-2%)
Vomiting (1-2%)
Diarrhea (1-2%)
Cramps (1-2%)
Pseudomembranous colitis (1-2%)
Pancreatitis (1-2%)
Frequency not defined
Muscular weakness
Edema
Flushing
Ataxia
Impaired concentration
Fever
Fatigue
Headache
Numbness
Behavioral changes
Dizziness
Warnings
Contraindications
Hypersensitivity to rifamycins
Concomitant administration of live bacterial vaccines
Contraindicated in patients receiving ritonavir-boosted saquinavir, because of increased risk of severe hepatocellular toxicity
Contraindicated in patients receiving atazanavir, darunavir, fosamprenavir, saquinavir, or tipranavir, because rifampin may cause substantial decreases in plasma concentrations of these antiviral drugs, which may result in loss of antiviral efficacy or development of viral resistance
Cautions
May decrease the effectiveness of oral contraceptive pills (OCPs)
Do not administer parenteral preparation IM or SC
Patients on regimens of >600 mg once or twice weekly may experience adverse reactions, including flulike syndrome
History of diabetes mellitus (rifampin may make diabetes management more difficult)
Regimens of >600 mg once or twice weekly may cause leukemia, anemia, or thrombocytopenia
Discontinue therapy if patient develops any signs of hepatocellular damage, including hyperbilirubinemia
Prolonged use may result in bacterial or fungal superinfection
Use with caution in patients with liver impairment and porphyria
Not for use in meningococcal disease; may be suitable for short-term use in asymptomatic carriers
Use with caution in patients with history of alcoholism and patients receiving additional medications that may cause hepatotoxicity
Rifampin is not recommended for intermittent therapy; caution patient against intentional or accidental interruption of daily dosage regimen; rare renal hypersensitivity reactions have been reported when therapy was resumed in such cases
Rifampin has enzyme-inducing properties that can enhance metabolism of endogenous substrates, including adrenal hormones, thyroid hormones, and vitamin d
Pregnancy and lactation
Pregnancy category: C
Effects unknown; reported to cross placental barrier and appear in cord blood; increased congenital malformations, primarily spina bifida and cleft palate reported in offspring of rodents given oral doses of 150-250 mg/kg/day during pregnancy; case reports of postnatal hemorrhage in mother and infant when administered during last few weeks of pregnancy
Lactation: Drug enters breast milk
Pregnancy categories
A: Generally acceptable. Controlled studies in pregnant women show no evidence of fetal risk.
B: May be acceptable. Either animal studies show no risk but human studies not available or animal studies showed minor risks and human studies done and showed no risk.
C: Use with caution if benefits outweigh risks. Animal studies show risk and human studies not available or neither animal nor human studies done.
D: Use in LIFE-THREATENING emergencies when no safer drug available. Positive evidence of human fetal risk.
X: Do not use in pregnancy. Risks involved outweigh potential benefits. Safer alternatives exist.
NA: Information not available.
Pharmacology of Rifadin, Rimactane (rifampin)
Mechanism of action
Inhibits DNA-dependent RNA polymerase by binding to beta subunit, which in turn blocks RNA transcription; potent enzyme inducer
Absorption
PO well absorbed; food may delay or slightly reduce peak
Peak plasma time: PO, 2-4 hr
Distribution
Highly lipophilic; crosses blood-brain barrier well, and relative diffusion from blood into CSF is adequate, with or without inflammation (exceeds usual MICs)
Protein bound: 80%
Metabolism
Metabolized by liver; undergoes enterohepatic recirculation
Elimination
Half-life: 3-4 hr (prolonged in hepatic impairment); in end-stage renal disease, 1.8-11 hr
Excretion: Feces (60-65%) and urine (~30%) as unchanged drug
Administration
PO
Take on empty stomach
IV Compatibilities
Solution: D5W (at 1.2 g/L within 4 hours)
IV Incompatibilities
Solution: NS (may be used within 24 hours)
Additive: Minocycline
Y-Site: Diltiazem
IV Preparation
Add 10 mL of SWI to 600 mg of rifampin in viaL
Before administration, solution may be added to 500 mL of D5W or 100 mL of D5W
IV Administration
Prepare and administer within 4 hours
In 500 mL of D5W: Infuse within 3 hours
In 100 mL of D5W: Infuse within 30 minutes
