PRIFTIN
Clinical safety rating: caution
Comprehensive clinical and safety monograph for PRIFTIN (PRIFTIN).
Inhibits bacterial RNA polymerase by binding to DNA-dependent RNA polymerase beta subunit, blocking RNA transcription initiation.
| Metabolism | Hepatic; primarily metabolized via deacetylation to 25-desacetylrifapentine; also hydrolyzed by esterases; CYP450 involvement not significant. |
| Excretion | Primarily hepatic metabolism to 25-desacetylrifapentine, followed by biliary/fecal elimination. Renal excretion of unchanged drug is <10%. |
| Half-life | 14-18 hours (rifapentine); 13-16 hours (25-desacetyl metabolite); prolonged to 30+ hours in hepatic impairment. |
| Protein binding | 97% bound to albumin. |
| Volume of Distribution | 70 L (approximately 1 L/kg in adults); distributes widely into tissues including lungs and macrophages. |
| Bioavailability | 70% (oral) with high-fat meal increases AUC by 40-60%. |
| Onset of Action | 2-4 hours after oral administration (detectable bactericidal activity in sputum). |
| Duration of Action | 24-48 hours due to prolonged half-life; supports intermittent dosing (e.g., once weekly in intensive phase). |
600 mg orally twice daily for 2 months, then 600 mg once daily for 4 months (total 6-month therapy). Administer with food.
| Dosage form | TABLET |
| Renal impairment | No dose adjustment required for mild to moderate renal impairment. For severe renal impairment (CrCl <30 mL/min), use with caution; no specific dose recommendation available. |
| Liver impairment | Mild to moderate hepatic impairment (Child-Pugh A or B): no dose adjustment. Severe hepatic impairment (Child-Pugh C): avoid use due to lack of data. |
| Pediatric use | 10-20 mg/kg orally twice daily for 2 months, then 10-20 mg/kg once daily for 4 months; maximum dose 600 mg twice daily during initial phase. Safety and efficacy in children <12 years not established. |
| Geriatric use | No specific dose adjustment recommended. Monitor renal function and hepatic function due to age-related declines. Use with caution in patients with significant renal impairment. |
| 1st trimester | Consult provider |
| 2nd trimester | Consult provider |
| 3rd trimester | Consult provider |
Clinical note
Comprehensive clinical and safety monograph for PRIFTIN (PRIFTIN).
| Breastfeeding | Unknown if excreted in human milk. M/P ratio not established. Use with caution in nursing mothers only if benefit outweighs potential risk of GI disturbances or hypersensitivity in infant. |
| Teratogenic Risk | Pregnancy Category C. First trimester: limited human data, animal studies show no teratogenicity but increased fetal resorptions at high doses. Second and third trimesters: no known specific malformation risk; consider risk of maternal toxicity (hepatotoxicity) which may indirectly affect fetus. |
| Fetal Monitoring |
■ FDA Black Box Warning
None.
| Serious Effects |
Hypersensitivity to rifapentine or any rifamycins, patients with acute porphyria.
| Precautions | Hepatotoxicity (monitor liver function), hyperuricemia, thrombocytopenia (especially with intermittent dosing), hypersensitivity reactions, potential for rifamycin resistance if used as monotherapy, urinary/oral secretions discoloration (red-orange), and drug interactions (induces CYP3A4 and P-glycoprotein). |
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| Monitor LFTs (ALT, AST, bilirubin) at baseline and monthly during pregnancy. Monitor CBC and renal function (serum creatinine) monthly. Assess for signs of hepatotoxicity or GI intolerance; fetal ultrasound in third trimester if maternal complications arise. |
| Fertility Effects | Animal studies show no impairment of fertility at clinical doses. Human data insufficient; theoretical risk from hormonal disruptions or testicular toxicity (based on rifamycin class) but not reported with priftin. No effect on female fertility documented. |