Gulhan, RezzanEryuksel, EmelOglu, Medine Gulcebi IdrizCulpan, YektaToplu, AylinKocakaya, DeryaTigen, ElifSengel, Buket ErturkSili, UluhanYildizeli, Sehnaz OlgunBalcan, Mehmet BaranElci, AbdullahBulut, CenkKaraalp, AtilaYananli, Hasan RaciGuner, Abdullah EmreHatipoglu, MustafaKarakurt, SaitKorten, VolkanRatnaraj, NevillePatsalos, PhilipAy, PinarOnat, Filiz2023-02-212023-02-212022-01-0110.1111/bcp.15227https://hdl.handle.net/11443/2255http://dx.doi.org/10.1111/bcp.15227This prospective observational study describes the pharmacokinetic characteristics of favipiravir in adult patients hospitalized for mild to moderate COVID-19 with a positive RT-PCR test. Favipiravir was administered for 5 days, with a loading dose of 3200 mg and a maintenance dose of 1200 mg/day. Serial blood samples were collected on Day 2 and Day 4 of the therapy. Laboratory findings of the patients (n = 21) and in-hospital mortality were recorded. Favipiravir concentrations exhibited substantial variability and a significant decrease during the treatment of COVID-19. The median favipiravir trough concentration (C0-trough) on Day 2 was 21.26 (interquartile range {[}IQR], 8.37-30.78) mu g/mL, whereas it decreased significantly to 1.61 (IQR, 0.00-6.41) mu g/mL on Day 4, the area under the concentration-time curve decreased by 68.5\%. Day 2 C0-trough of female patients was higher than male patients. Our findings indicate that favipiravir concentrations show significant variability during the treatment of COVID-19 and therapeutic drug monitoring may be necessary to maintain targeted concentrations.COVIDfavipiravirpharmacokineticstherapeutic drug monitoringArticleWOS:000752673600001