Paxlovid (nirmatrelvir/ritonavir) is an oral medication indicated for patients recently diagnosed with COVID-19 and who are at high risk of deterioration. This drug received an emergency use authorization (EUA) from the FDA on December 2021. The official EUA reads :
The U.S. Food and Drug Administration has issued an EUA for the emergency use of the unapproved PAXLOVID which includes nirmatrelvir, a SARS-CoV-2 main protease (Mpro: also referred to as 3CLpro or nsp5 protease) inhibitor, and ritonavir, an HIV-1 protease inhibitor and CYP3A inhibitor, for the treatment of mild-to-moderate coronavirus disease 2019 (COVID-19) in adults and pediatric patients (12 years of age and older weighing at least 40 kg) with positive results of direct severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) viral testing, and who are at high risk for progression to severe COVID-19, including hospitalization or death.
According to the fact sheet for healthcare providers cited above, Paxlovid is to be taken twice daily for 5 days:
Ritonavir is administered with nirmatrelvir as a pharmacokinetic enhancer resulting in higher systemic concentrations and longer half-life of nirmatrelvir, thereby supporting a twice daily administration regimen.
The reported elimination half-life of Nirmatrelvir in the presence of ritonavir is ~6 hours .
A healthcare professional colleague inquired about a Muslim patient who asked if it is possible to adjust administration times according to meal times during Ramadan. Specifically, they asked whether it would be possible to take the medicine at 4:30 and 19:00, i.e. at the beginning and the end of the daily fast. In essence this means that the dosing intervals would alternate between 14.5 hours and 9.5 hours, instead of 12 hours. How would this adjustment impact the drug's efficacy, if at all?