PhD candidate Colorado State University Fort Collins, CO, United States
Abstract: Background– Antiviral drugs like EIDD-2801 (molnupiravir; MPV) have been successfully used in treatment of feline infectious peritonitis (FIP). Previous study on pharmacokinetics of MPV in healthy cats showed promise for its use and safety. Hypothesis/Objectives– To determine the pharmacokinetics of molnupiravir in cats with naturally occurring FIP by measuring MPV and EIDD-193 (β-D-N4-hydroxycytidine; NHC) serum levels. Animals– Seven cats diagnosed with naturally occurring FIP treated with MPV. Methods– Blood was collected at 1,2,4,6 and 12h post oral MPV administration and at 12h post-pill administration 7 days later. Serum concentrations of MPV and NHC were determined using a previously published high performance liquid chromatography tandem-mass spectrometry (HPLC-MS/MS) method. Results– The mean dose of MPV was 15.44mg/kg (SD± 1.82). The mean peak serum concentration of MPV (Cmax) after a single PO dose of MPV was 6.0µM (SD± 2.8). The mean peak serum concentration of NHC (Cmax) after a single PO dose of MVP was 1551ng/mL (SD± 720). Time to reach Cmax (Tmax) was 2.6h (SD± 1.4); and elimination half-life was 1.6 h (SD± 1.1). No accumulation of drug was seen in trough levels following daily dosing for 7 days. Combined serum MPV and NHC levels for all cats at 1, 2, 4, 6 and 12 hours post MPV administration are shown in Figures 1 and 2. Conclusions and clinical importance– This study supports the use of MPV in the treatment of FIP. The low MPV levels may be explained by fast conversion to its active metabolite NHC.
