Chemical formula: C₅H₄FN₃O₂ Molecular mass: 157.104 g/mol PubChem compound: 492405
Favipiravir interacts in the following cases:
Favipiravir is a CYP2C8 inhibitor. Inhibition of CYP2C8 increases blood level of repaglinide and adverse reactions to repaglinide may occur.
Favipiravir is a aldehyde oxidase (AO) inhibitor. Inhibition of aldehyde oxidase (AO) may decrease blood level of active forms of famciclovir and sulindac. Efficacy of these drugs may be reduced.
Blood uric acid level increases. When pyrazinamide 1.5g once daily and favipiravir 1200 mg/400 mg BID were administered, the blood uric acid level was 11.6 mg/dL when pyrazinamide was administered alone, and 13.9 mg/dL in combination with favipiravir. Reabsorption of uric acid in the renal tubule is additively enhanced.
Favipiravir is partly metabolized by xanthine oxidase (XO). Interaction with xanthine oxidase (XO) may increase blood level of favipiravir and adverse reactions to favipiravir may occur.
Do not administer favipiravir to women known or suspected to be pregnant.
Early embryonic deaths (rats) and teratogenicity (monkeys, mice, rats and rabbits) have been observed in animal studies with exposure levels similar to or lower than the clinical exposure.
When administering favipiravir to lactating women, instruct to stop lactating.
The major metabolite of favipiravir, a hydroxylated form, was found to be distributed in breast milk.
Favipiravir has never been administered with the approved dosage. In Japanese clinical studies and the global phase III study (studies conducted with dose levels lower than the approved dosage), adverse reactions were observed in 100 of 501 subjects (19.96%) evaluated for the safety (including abnormal laboratory test values). Major adverse reactions included increase of blood uric acid level in 24 subjects (4.79%), diarrhoea in 24 subjects (4.79%), decrease of neutrophil count in 9 subjects (1.80%), increase of AST (GOT) in 9 subjects (1.80%), increase of ALT (GPT) in 8 subjects (1.60%).
The following clinically significant adverse reactions have been reported with other anti-influenza virus agents. Patients should be carefully monitored, and if any abnormality is observed, the treatment should be discontinued and appropriate measures should be taken.
If the following adverse reactions occur, appropriate measures should be taken according to the symptoms.
| ≥1% | 0.5 - <1% | <0.5% | |
|---|---|---|---|
| Hypersensitivity | Rash | Eczema, pruritus | |
| Hepatic | AST (GOT) increased, ALT (GPT) increased, γ-GTP increased | Blood ALP increased, blood bilirubin increased | |
| Gastrointestinal | Diarrhoea (4.79%) | Nausea, vomiting, abdominal pain | Abdominal discomfort, duodenal ulcer, haematochezia, gastritis |
| Hematologic | Neutrophil count decreased, white blood cell count decreased | White blood cell count increased, reticulocyte count decreased, monocyte increased | |
| Metabolic disorders | Blood uric acid increased (4.79%), blood triglycerides increased | Glucose urine present | Blood potassium decreased |
| Respiratory | Asthma, oropharyngeal pain, rhinitis, nasopharyngitis | ||
| Others | Blood CK (CPK) increased, blood urine present, tonsil polyp, pigmentation, dysgeusia, bruise, vision blurred, eye pain, vertigo, supraventricular extrasystoles |
Note 1: Adverse reactions observed in Japanese clinical studies and the global phase III clinical study (studies conducted with dose levels lower than the approval dosage).
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