Study objectives: The clinical efficacy and cost-effectiveness of influenza antiviral use are controversial, with recent analyses suggesting potentially limited value. Thus, the objectives of this study were to describe influenza antiviral expenditures overall and by health care setting over a 10-year period (2003-2012) and to assess the correlation between outpatient influenza antiviral prescription use and influenza-like illness (ILI) outpatient visits.
Design: Retrospective, cross-sectional study.
Data sources: IMS Health National Sales Perspectives and Xponent databases and Centers for Disease Control and Prevention ILINet national influenza surveillance system database.
Patients: All prescriptions for oseltamivir, rimantadine, or zanamivir from community pharmacies, mail order pharmacies, clinics, nonfederal hospitals, and other health care settings (federal hospitals, military facilities, jails and prisons, universities, staff-model health maintenance organizations, veterinary hospitals and clinics, and long-term care facilities) between January 1, 2003, and December 31, 2012.
Measurements and main results: Prescribing rates were calculated (prescriptions/1000 persons) for each year from 2003 to 2012 by using U.S. Census Bureau data. Influenza season was defined as July 1-June 30 of each calendar year. Linear regression assessed the correlation between influenza antiviral expenditures, prescription use, and ILI diagnoses. From 2003 to 2012, influenza antiviral drug expenditures accounted for $3.74 billion, with the majority from community pharmacies. After adjusting for inflation, no growth was observed for expenditures. A total of 32.8 million influenza antiviral prescriptions were dispensed from community pharmacies during the study period, and these prescriptions experienced 133.2% growth from 2003 to 2012. One third of expenditures and one quarter of dispensed prescriptions were in 2009. Influenza seasons were correlated with ILI and antiviral prescriptions. Annual community pharmacy expenditures were also associated with influenza antiviral prescriptions dispensed over the 10-year period.
Conclusion: Influenza antivirals totaled $3.74 billion in the United States from 2003 to 2012, with the majority in 2009 and from community pharmacies. Influenza antivirals constituted a small proportion of total medication expenditures, but unforeseen pandemics resulted in unusually high use and expenditures. Influenza antiviral prescriptions dispensed from community pharmacies were associated with ILI and drug expenditures.
Keywords: adamantanes; influenza; neuraminidase inhibitors; prescribing practices.
© 2015 Pharmacotherapy Publications, Inc.