Antimicrobials
Paxlovid (Nirmatrelvir/ritonavir)

Paxlovid (Nirmatrelvir/ritonavir)

N/A
N/A
Currently N/A

Spectrum of Activity

General Information

Paxlovid is a recommended treatment option for mildly ill COVID-19 patients (patients who do not require new or additional supplemental oxygen from their baseline status) who:

  • Present within 5 days of symptom onset; AND
  • Are at higher risk of severe disease (as per Ontario Health recommendations):
    • 60 years or older
    • 18-59 years old who are immunocompromised
    • 18-59 years old who are at higher risk of severe COVID-19
  • CAUTION: Pharmacist consultation important to mitigate significant drug-drug interactions
  • Renal function
  • Liver function
  • Drug interactions
  • Dysgeusia (taste disturbance)
  • Diarrhea
  • Hypertension
  • Myalgia
  • Vomiting and headache
  • Pregnancy
    • Paxlovid has not been studied in this population
  • Breastfeeding
    • OSAT recommends not to breastfeed for duration of Paxlovid treatment and for 4 days afterwards (during which time breast milk should be pumped and discarded)
  • Individuals with uncontrolled or undiagnosed HIV
    • Potential for development of resistance to HIV protease inhibitors while on ritonavir alone

Antimicrobial class: Antiviral (Paxlovid is a ritonavir boosted SARS-CoV-2 main protease inhibitor (nirmatrelvir) that prevents viral replication)

Half-life: ~6 hours (longer in those with renal impairment)

Metabolism: Ritonavir is a potent inhibitor of CYP3A4 and various drug transporters (e.g. P-glycoprotein). Ritonavir and nirmatrelvir are both CYP3A4 substrates

Excretion: renal primary route (nirmatrelvir); hepatic primary route (ritonavir)