Background and Importance New drugs have been investigated with the aim of preventing serious pathology in high-risk patients with COVID. As a result, nirmatrelvir-ritonavir emerged, approved by the European Medicines Agency in December 2021 thanks to the pivotal EPIC-HR clinical trial.

Aim and Objectives To analyse the effectiveness and pharmacological interaction profile of nirmatrelvir-ritonavir in patients diagnosed with SARS-Cov2.

Material and Methods Retrospective study in which patients diagnosed with mild-moderate SARS-Cov2 for whom treatment with nirmatrelvir-ritonavir was requested from the approval of the drug until 08/31/2022 were preselected. Patients who received treatment were included. The primary effectiveness endpoint was hospital admission or death from any cause through day 28. As a secondary variable, the profile of pharmacological interactions between nirmatrelvir-ritonavir and the patients‘ medication and its management. Selection of patients, demographic and clinical data were obtained from the electronic medical record. Descriptive statistical analysis was performed using Excel^®16.48.

Results We preselected 86 patients, 37 (43.02%) did not receive treatment. The reasons for non-indication were: patients not considered high risk 30/37 (81.08%), receiving oxygen therapy 4/37 (10.82%), >6 days of symptoms, unmanageable interactions and received remdesivir, 1/37 (2.70%) each one. Obtaining a final sample of 49 patients. Mean age was 67.5 years(SD=16) and 25(51.02%) of them were men. Indication’s reasons were: high-risk immunocompromised patients 32/49 (65.31%), vaccinated >6 months ago over 80 years with risk factor 14/49 (28.57%), unvaccinated over 80 years 2/49 (4.08%), unvaccinated over 65 years with a risk factor 1/49 (2.04%). Of these, 10/49 (20.41%) required adjustment to renal function. An event (hospital-admission or death) during the 28 days after the start of treatment was registered in 16/49 (32.65%) patients. Of these 14 (28.57%) events were hospital-admission and 2 (4.08%) deaths. We detected 77 interactions in 39/49 (79.59%) patients [2.14 interactions/patient; SD=1.42], that required: to monitor 55/77 (71.43%), suspend treatment and reintroduce it 3 days after 20/77 (25.98%) and reduce dose 2/77 (2.59%). Main therapeutic groups with interactions: statins 14/77 (18.17%), metamizole 9/77 (11.68%), calcium channel blockers 8/77 (10.38%), antidepressants 5/77 (6.49%),opioids 4/77 (5.19%), direct oral anticoagulants 4/77 (5.19%), and tamsulosin 4/77 (5.19%).

Conclusion and Relevance It seems that real-life results of nirmatrelvir-ritonavir are inferior to those obtained in the pivotal RCT, due to higher number of hospital admissions. Most patients presented interactions, which could be managed in a simple way through temporary suspension and monitoring.

Conflict of Interest No conflict of interest