Introducing Ritonavir-Boosted Nirmatrelvir (Paxlovid) at the National Center for Global Health and Medicine: Surveys Following its Introduction

Background: Paxlovid, an oral COVID-19 drug, is a ritonavir-containing drug, and as it significantly affects the activities of various drug-metabolizing enzymes, drug-drug interactions (DDIs) are a significant concern during clinical use of the drug. However, there are few reports on the observations during actual clinical use of Paxlovid.Methods: We developed a list of drugs that should only be used with caution along with Paxlovid and used a DDI search tool to easily check for DDIs during use of Paxlovid. We also investigated the number of inquiries about DDIs, the number of suggestions made by pharmacists, and the number of suggestions adopted by physicians in the 33 patients prescribed with Paxlovid during the 3-month period from February 15, 2022, to May 14, 2022. In addition, as part of the patient follow-up conducted after the start of Paxlovid, outpatients who were on medications that needed to be temporarily discontinued during Paxlovid use were contacted by telephone to confirm their medication adherence/medication discontinuation compliance status and the timing of resumption of the temporarily discontinued medications.Results: There were 28 inquiries regarding DDIs, and the adoption rate of the pharmacists' suggestions by the treating physicians was 100%. One out of the seven patients who we contacted by telephone did not clearly understand the correct timing for resuming the temporarily discontinued medications. The pharmacist gave instruction again to the patient over the phone and subsequently confirmed, in a follow-up phone call, that the medication had been resumed without error.Discussion: Pharmacists can contribute to the proper use of Paxlovid and reduce barriers to prescribing Paxlovid through management of DDIs and patient follow-up.