Address Nirmatrelvir/Ritonavir (Paxlovid) Interactions

Please see the FDA announcement authorizing pharmacists to prescribe Paxlovid with certain limitations.

You can help answer questions when patients with COVID-19 taking nirmatrelvir/ritonavir (Paxlovid) present to the hospital.

It’s too soon to say if patients taking nirmatrelvir/ritonavir should continue it on admission. It’s okay to complete the course...but you’ll likely need to use a patient’s home supply.

Be ready to manage interactions...since the ritonavir component is a strong CYP3A4 and P-glycoprotein inhibitor.

Ask patients if any of their home meds were stopped or adjusted due to interactions when nirmatrelvir/ritonavir was started. Include these details in your EHR’s home med section.

When starting meds in-house, consider using a checker, such as COVID19-DrugInteractions.org...especially if your EHR software doesn’t include nirmatrelvir/ritonavir yet.

For example, continue to use oral or inhaled steroids...despite labeled warnings that adding nirmatrelvir/ritonavir may increase risk of adrenal suppression. Five days of the combo isn’t likely a concern.

But stop nirmatrelvir/ritonavir if adding clopidogrel for a new stent or for other patients at high clot risk...ritonavir inhibits the conversion of clopidogrel to its active form.

Also stop nirmatrelvir/ritonavir if starting rivaroxaban...due to increased bleeding risk.

Point out that apixaban isn’t clear-cut. Manage based on dose and indication. For instance, if adding apixaban for VTE treatment, consider stopping nirmatrelvir/ritonavir.

At discharge, address any home meds that were stopped or adjusted when nirmatrelvir/ritonavir was started.

For example, if apixaban for atrial fib was reduced to 2.5 mg bid, increase back to 5 mg bid 3 days after completing the course.

Go to our resource, Treatments of Interest for COVID-19, for renal dose adjustments, other interaction checkers, etc.

Key References

  • https://www.fda.gov/media/155050/download (6-27-22)
  • https://www.covid19-druginteractions.org/checker (6-27-22)
  • https://www.idsociety.org/globalassets/idsa/practice-guidelines/covid-19/treatment/idsa-paxlovid-drug-interactions-resource-5-6-22-v1.1.pdf (6-27-22)
  • https://emergency.cdc.gov/han/2022/pdf/CDC_HAN_467.pdf (6-27-22)
Hospital Pharmacist's Letter. July 2022, No. 380702



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