Nirmatrelvir Ritonavir

FDA emergency use in 2022 for high risk outpatients age >12 years (and >40 kg) within 5 days of onset
Emergency Use authorization in U.S. will expire at end of 2023 (and cost expected to $1400/course)

Oral Protease Inhibitor specific to SARS-COV-2 viral replication (Ritonavir slows nirmatrelvir metabolism)

Reduces risk of hospitalization or death at 28 days by 89% if started within first 3 days
NNT 18 unvaccinated, high risk patients to prevent one hospitalization or death

Distributed in Blister pack (pharmacist adjusts based on eGFR)
eGFR>=60 ml/min
1. Take Nirmatrelvir 300 (2 tabs) AND Ritonavir 100 mg twice daily for 5 days
eGFR 30 to 59
1. Take Nirmatrelvir 150 (1 tab) AND Ritonavir 100 mg twice daily for 5 days

Dysgeusia
Diarrhea
Hypertension
Myalgias
Risk of COVID-19 rebound (recurrent symptoms within 1 week after finishing Paxlovid)
1. Do not repeat Paxlovid course, but re-quarantine 5 days and mask for 10 days

Numerous Drug Interactions, esp. for Ritonavir (esp. CYP3A)
Important interactions include Salmeterol, DOACs (esp. Rivaroxaban), Phenytoin and Clopidogrel
Use a Drug Interaction checker

Pregnancy
1. Unknown safety, but recommended when indicated as of 2024
2. Pregnancy itself is a higher risk condition, and risk increases with other comorbidities
Lactation
1. Unknown safety, but recommended when indicated as of 2024
2. Lactation may continue while using Paxlovid
Resources
1. Pregnancy, Lactation, and COVID-19 Therapeutics (NIH)
  1. https://www.covid19treatmentguidelines.nih.gov/special-populations/pregnancy/pregnancy-lactation-and-covid-19-therapeutics/