Dosing and uses of Rifamate (rifampin-isoniazid)
Adult dosage forms and strengths
rifampin/isoniazid
capsule
- 300mg/150mg
Tuberculosis
2 caps PO BId
Administration
Take on empty stomach with full glass of water
Pediatric dosage forms and strengths
<15 years old: safety & efficacy not established
Warnings
Contraindications
Hypersensitivity to isoniazid, rifamycins
Acute liver dz, severe hepatic damage, acute gout
Rifampin is contraindicated in patients receiving ritonavir-boosted saquinavir due to an increased risk of severe hepatocellular toxicity
Rifampin is contraindicated in patients receiving atazanavir, darunavir, fosamprenavir, saquinavir, or tipranavir due to the potential of rifampin to substantially decrease plasma concentrations of these antiviral drugs, which may result in loss of antiviral efficacy and/or development of viral resistance
Cautions
History of diabetes mellitus (may make diabetes management more difficult)
Rifampin is not recommended for intermittent therapy; caution patient against intentional or accidental interruption of daily dosage regimen since rare renal hypersensitivity reactions have been reported when therapy was resumed in such cases
Rifampin has enzyme induction properties that can enhance the metabolism of endogenous substrates including adrenal hormones, thyroid hormones, and vitamin d
Pregnancy and lactation
Pregnancy: C
Rifampin: 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
Isoniazid: Embryocidal effects reported in both rats and rabbits, although no congenital abnormalities observed in mammalian offspring when given during pregnancy
Lactation: Isoniazid is known to be secreted into breast milk; caution advised
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.
