Introduction
Favipiravir was approved in Japan for use in the event of an outbreak of novel or re-emerging influenza viral infections, where other influenza antiviral drugs are either not or insufficiently effective [1]. Favipiravir is a new antiviral drug against influenza. Favipravir is metabolized into favipiravir ribosyl triphosphate (favipiravir RTP) by an intracellular enzyme, and favipiravir RTP selectively inhibits RNA polymerase (RNA-dependent RNA polymerase) of the influenza virus, preventing replication of the influenza virus. The mechanism of action of favipiravir is the selective inhibition of RNA polymerase by favipiravir ribosyl triphosphate formed by cellular enzymes in the influenza virus leading to antiviral activity [2]. In an open-label comparative controlled study of patients with Covid-19, those treated with favipiravir apeared to have faster viral clearance and higher rates of improvement in chest imaging, and in another prospective, randomized, controlled, open-label multicenter trial favipiravir significantly improved the latency to relief for pyrexia and cough [3,4].
The bioequivalence study is required for generic orally administered Favipiravir products by certain regulatory authorities [5, 6]. Therefore, this study aims to compare the pharmacokinetic properties of a generic formulation to the reference product and to demonstrate the bioequivalence of the products with respect to the rate and extent of absorption of Favipiravir in healthy male subjects under fasting conditions.