Spectrum of Activity


General Information

Adverse events (incidence ≥1% and ≥5 patient difference):

  • dysgeusia (6%)
  • diarrhea (3%)
  • hypertension (1%)
  • myalgia (1%)

(Studies are limited - possible that all adverse effects, including those that are rare but serious, are not known)

Nirmatrelvir tablets co-packaged with ritonavir tablets:

  • Nirmatrelvir tablets, 150 mg are oval, pink immediate-release, film-coated tablets debossed with “PFE” on one side and “3CL” on the other side.
  • Ritonavir tablets, 100 mg are white film-coated ovaloid tablets debossed with the "a" logo and the code NK.

Nirmatrelvir tablets and ritonavir tablets are supplied in separate cavities within the same child resistant blister card.


  • Can be taken with or without food

Missed Dose:

  • Missed dose within 8 hours of the time it is usually taken, the patient should take it as soon as possible and resume the normal dosing schedule.
  • Missed dose by more than 8 hours, the patient should not take the missed dose and instead take the next dose at the regularly scheduled time.
  • The patient should not double the dose to make up for a missed dose.

Click here to access the product monograph

Antimicrobial Class:

  • Nirmatrelvir is a protease inhibitor, active against the SARS-CoV-2 3CL protease, which halts viral replication.
  • Ritonavir is an HIV-1 protease inhibitor not active against SARS-CoV-2.
  • Ritonavir inhibits the CYP3A-mediated metabolism of nirmatrelvir and is used as a pharmacokinetic booster resulting in increased plasma concentrations of nirmatrelvir.

Average half-life:

  • Nirmatrelvir (when given with ritonavir): 6.05 ± 1.79 hours; Ritonavir: 6.15 hours