Fluoxetine pharmacokinetics and tissue distribution suggest a possible role in reducing SARS-CoV-2 titers

Background.  Recent in vitro studies have shown fluoxetine inhibits the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) pathogen, including variants B.1.1.7 and B.1.351, SARS-CoV-2 spike mutations (E484K, K417N, N501Y), and one retrospective clinical study reported fluoxetine exposure at a median dose of 20 mg in patients with the SARS-CoV-2 coronavirus disease 2019 (COVID-19) had a significantly lower risk of intubation and death. The aim of this study is to conduct in silico population pharmacokinetic dosing simulations to quantify the percentage of patients achieving a trough level for the effective concentration resulting in 90% inhibition (EC90) of SARS-CoV-2 as reported in Calu-3 human lung cells.  Methods.  Population pharmacokinetic parameter estimates for a structural one-compartment model with first-order absorption were used to simulate fluoxetine pharmacokinetic data. A population of 1,000 individuals were simulated at standard fluoxetine doses (20 mg/day, 40 mg/day, and 60 mg/day) to estimate the percentage of the patients achieving a trough plasma level for the EC90 SARS-CoV-2 inhibitory concentration for a 10 day treatment period. All analyses were conducted via statistical programming in R.  Results.  Standard fluoxetine antidepressant doses resulted in a range of 81% to 97% of the patient population achieving a trough target plasma concentration of 23.2 ng/ml at day 10 and translates to a lung-tissue distribution coefficient of 60-times higher (EC90 of 4.02 mM). At a dose of 40 mg per day, at least 87% of patients will reach the trough target EC90 concentration within three days.   Conclusion. Overall, the findings of this population pharmacokinetic dosing study corroborates in vitro and observational clinical studies reporting the first selective serotonin reuptake inhibitor fluoxetine inhibits the SARS-CoV-2 pathogen at commonly treated doses in the practice of psychiatry.