PREVALENCE OF POTENTIAL DRUG-DRUG INTERACTIONS WITH RITONAVIR-CONTAINING COVID-19 MEDICATIONS AMONG THE ADULT PATIENT POPULATION IN AUSTRALIA: ANALYSIS OF PHARMACEUTICAL BENEFITS SCHEME 10% SAMPLE (PBS10) CLAIMS

INTRO: Oral antiviral agents with differing modes of action are now available for the treatment of COVID-19. However, potentially life-threatening drug-drug interactions (DDIs) may occur if patients’ underlying co-morbidities are treated with medications that are contraindicated with ritonavir-containing antivirals. This study evaluated the prevalence and severity of potential DDIs (pDDIs) with ritonavir-containing COVID-19 oral antiviral therapy among the Australian population. METHODS: Adult patients supplied with ≥1 medication between January 1, 2019, and December 31, 2019, were identified in the PBS10 dataset, a longitudinal, random 10% sample of the national Pharmaceutical Benefits Scheme (PBS) data for supplied prescriptions. Patients receiving medications that have pDDIs with a ritonavir-containing COVID-19 antiviral treatment were classified as the pDDI group, using data sources from University of Liverpool, Lexicomp®, or the US Food and Drugs Administration. FINDINGS: Over 1,434,000 patients in the PBS10 were supplied with ≥1 medication during the study period. The majority (58.8%) had been prescribed at least one medication with pDDI with ritonavir-containing treatment. Among all patients with pDDIs, 43.3% of them were major or contraindicated, followed by moderate (15.1%), and minor pDDIs (1.9%). Patients with cancer had the highest prevalence of contraindicated or major pDDIs (79.5%), followed by dementia and/or Alzheimer's (77.2%), and diabetes (73.8%). Elderly patients (≥60 years old) also had a higher prevalence of contradicted or major pDDI (65.4%) than the general patient population. CONCLUSION: Our results demonstrated that one-third of the Australian adult population in the PBS10 dataset may be classified as contraindicated with ritonavir-containing COVID-19 therapies. The prevalence of pDDI is much higher in elderly patients and in patients with certain co-morbidities. Health care providers will need to evaluate patients carefully should they be eligible for COVID-19 oral antiviral treatments. Alternative therapies should be considered as patients may be precluded from being treated with ritonavir-containing therapies owing to pDDIs.