NOVEL ULTRA-PERFORMANCE LIQUID CHROMATOGRAPHY METHOD FOR CONCURRENT ESTIMATION AND PHARMACOKINETIC ANALYSIS OF FAVIPIRAVIR AND MOLNUPIRAVIR IN RAT PLASMA

Objectives: The objective of this study was to establish a rapid and sensitive ultra-performance liquid chromatography (UPLC) method for the simultaneous estimation of molnupiravir and favipiravir in rat plasma using nirmatrelvir as internal reference. Methods: The separation was performed on Waters Acquity UPLC BEH C18 (100 mm × 2.1 mm, 1.7 μm) by isocratic elution with a buffer containing 1 mL of formic acid in 1 L of water and the mixer of two components such as buffer and acetonitrile in the ratio of 70:30 as mobile phase with flow rate was 0.3 mL/min at ambient temperature. Results: Analysis was carried out within 3 min over a good linear concentration range from 100 ng/mL to 4000 ng/mL for both drugs of favipiravir (r2=0.9999±0.018) and molnupiravir (r2=0.9998±0.006). This method has been successfully applied, exploring favipiravir (3.33 mg/kg) and molnupiravir (3.33 mg/kg) with internal standard nirmatrelvir extracted from rat plasma using liquid–liquid extraction. Conclusion: The drugs were stable throughout the stability studies according to US Food and Drug Administration guidelines, just because, the validated approach has successfully conducting to the pharmacokinetic studies of two drugs.