FAVLYXA
Clinical safety rating: caution
Comprehensive clinical and safety monograph for FAVLYXA (FAVLYXA).
Acyclic nucleoside phosphonate prodrug that inhibits viral RNA-dependent RNA polymerase (RdRP) by competing with adenosine triphosphate (ATP). It incorporates into nascent viral RNA causing chain termination after incorporation of the first 1-2 nucleotides.
| Metabolism | Metabolized by esterases (CES1 and CES2) and phosphoramidase (HINT1) to its active metabolite remdesivir triphosphate. Not significantly metabolized by CYP450 enzymes. |
| Excretion | Primarily renal excretion of unchanged drug (approx. 85%) with biliary/fecal elimination accounting for the remainder (approx. 15%). |
| Half-life | Terminal elimination half-life approximately 5-7 hours in patients with normal renal function; prolonged in renal impairment (up to 24 hours in severe impairment). |
| Protein binding | Approximately 30-35% bound to plasma proteins, primarily albumin. |
| Volume of Distribution | Volume of distribution approximately 1.2 L/kg, suggesting extensive tissue distribution. |
| Bioavailability | Oral bioavailability approximately 80-90%. |
| Onset of Action | Oral: Clinical effect observed within 30-60 minutes following oral administration. |
| Duration of Action | Duration of clinical effect is approximately 12-24 hours, correlating with plasma concentration above the therapeutic threshold. |
| Molecular Weight | 472.5 |
200 mg orally twice daily for 10 days.
| Dosage form | SOLUTION |
| Renal impairment | If GFR 30-50 mL/min: reduce to 200 mg once daily. If GFR <30 mL/min or on hemodialysis: not recommended. |
| Liver impairment | No dose adjustment required for mild to moderate hepatic impairment (Child-Pugh A or B). Not studied in severe impairment (Child-Pugh C); use caution. |
| Pediatric use | For children ≥40 kg: 200 mg orally twice daily for 10 days. For children <40 kg: 4 mg/kg twice daily for 10 days (maximum 200 mg per dose). |
| Geriatric use | No specific dose adjustment; monitor renal function as elderly more likely to have decreased creatinine clearance. |
| 1st trimester | Animal studies show teratogenicity; avoid use in first trimester unless no alternative. |
| 2nd trimester | Limited human data; potential fetal harm; use only if benefit outweighs risk. |
| 3rd trimester | Neonatal CNS depression and withdrawal possible; avoid near term. |
Clinical note
Comprehensive clinical and safety monograph for FAVLYXA (FAVLYXA).
| Placental transfer | Crosses placenta; cord blood levels approximately 70% of maternal levels. |
| Breastfeeding | Excreted in human milk; potential for infant CNS effects; alternative agents preferred. |
| Lactation Rating | L4 (Possibly Hazardous) |
■ FDA Black Box Warning
No FDA black box warning.
| Serious Effects |
Hypersensitivity to favipiravirSevere hepatic impairment
| Precautions | Hypersensitivity reactions including infusion-related reactions and anaphylaxis, Increased hepatic transaminases; monitor liver function tests prior to and during treatment, Risk of reduced antiviral activity when coadministered with strong inducers of CYP450 or transporters, Use in pregnancy only if potential benefit outweighs risk; limited human data available, Not recommended for patients with eGFR <30 mL/min unless potential benefit outweighs risk |
| Food/Dietary | No specific food interactions reported. However, avoid excessive intake of high-purine foods (e.g., organ meats, shellfish) due to risk of elevated uric acid levels. |
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| Teratogenic Risk | Favipiravir is contraindicated in pregnancy. Animal studies show teratogenicity, embryotoxicity, and fetal loss across all trimesters. Based on mechanism of action (RNA polymerase inhibition), it is expected to cause fetal harm. There is no safe trimester. |
| Fetal Monitoring | Pregnancy testing before initiation and monthly during therapy. Use effective contraception during and for 1 month after. Monitor for fetal anomalies if exposure occurs; consult maternal-fetal medicine. |
| Fertility Effects | Animal studies indicate impaired fertility (reduced implantation and litter size) at clinically relevant doses. Human data lacking; risk of reversible fertility impairment. |
| Clinical Pearls | Favlyxa (favipiravir) is a selective RNA polymerase inhibitor used for influenza and COVID-19 in some regions. Monitor for hyperuricemia, as it inhibits xanthine oxidase; avoid in pregnancy and breastfeeding due to teratogenicity in animal studies. Reduce dose in renal impairment (eGFR <30 mL/min not recommended). Drug levels may be reduced by concomitant pyrazinamide, as it decreases favipiravir plasma concentration. |
| Patient Advice | Take exactly as prescribed, with or without food. Do not skip doses or stop early. · Avoid alcohol during treatment; may increase risk of liver damage. · Inform your doctor if you have liver or kidney problems, gout, or are pregnant or breastfeeding. · Use effective contraception during and for 1 month after treatment. Do not breastfeed during therapy. · Report symptoms of gout (joint pain, swelling), nausea, vomiting, or yellowing of skin/eyes immediately. |