Background.

The oral antiviral nirmatrelvir/ritonavir interacts with a range of drugs. Candidate patients to receive this antiviral agent are usually vulnerable, multipathological and polymedicated. The objective is to evaluate the pharmaceutical validation prior to the administration of the antiviral.

Material and methods.

Drug-drug interactions between nirmatrelvir/ritonavir and patients’ usual treatment medications were checked in product information and in the UpToDate® and the University of Liverpool® interaction tools. We included validated prescriptions between April/2022 and April/2023 by a Primary Care pharmacist.

Results.

Of the 159 study patients, 168 interactions were found in 83 individuals, which may have led to changes of their usual treatment. Statins (25.6%), anticoagulants (10.7%), and antihypertensives (10.7%) were the most frequently implicated therapeutic groups. Discontinuation (53.0%) and dose reduction (22.6%) were the most common treatment changes.

Conclusions.

Our search of potential drug interactions and subsequent dose adjustments and modifications of the patient’s usual treatment has helped avoid potential toxicities ensuring a safe use of nirmatrelvir/ritonavir.