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Background: Complications of influenza are a major cause of morbidity and mortality during the influenza season. Clinical trials of zanamivir have reported a reduced incidence of influenza complications among high-risk patients.Objectives: This retrospective study sought to determine whether the use of zanamivir lowers the risk of acute influenza complications in a broader population, based on an analysis of claims data from a large managed care organization.Methods: Medical and pharmacy health insurance claims data from October 1, 1999, through April 30, 2000, were compiled for UnitedHealthcare members in 19 states. All patients with a diagnosis of influenza (International Classification of Diseases, Ninth Revision, Clinical Modification diagnostic code 487.xx) associated with a physician visit were identified. From these, all patients were selected who had received zanamivir on the same day as the diagnosis of influenza. The propensity score matching technique was used to identify a comparison group with similar health service utilization and comorbidities who received a diagnosis of influenza but no antiviral therapy. Follow-up started the day after the influenza diagnosis and continued for 21 days.Results: From the 43,741 patients originally identified, 2341 were selected who received a simultaneous diagnosis of influenza and a prescription for zanamivir. The untreated comparator group numbered 2337. Fewer zanamivir patients than untreated patients were hospitalized for complications, and the absolute risks were low (0.6% and 1.0%, respectively; risk ratio [RR], 0.58; 95% CI, 0.30–1.12). Zanamivir-treated patients had an excess of outpatient visits (16.9% vs 14.5%; RR, 1.16; 95% CI, 1.02–1.33) and antibiotic use (16.3% vs 14.8%; RR, 1.10; 95% CI, 0.97–1.26), although the RRs were modest.Conclusions: In the setting of a large managed care plan, patterns of influenza complications were similar in zanamivir-treated and untreated patients with a diagnosis of influenza. The results of this study are in contrast to those of published clinical trials reporting a reduction in the risk of influenza complications in zanamivir-treated patients. [Copyright &y& Elsevier]

Background: Inhaled zanamivir is indicated for treatment of uncomplicated acute illness due to influenza A and B viruses in patients aged ≥12 years who have been symptomatic for no more than 2 days.Objective: The primary objective of this study was to estimate the incidence of adverse respiratory events among zanamivir-treated patients under conditions of usual care.Methods: The Ingenix research database includes insurance claims for all dispensations, inpatient and outpatient services, and procedures including the associated diagnoses and costs for a subset of all enrolled UnitedHealthcare members. We identified all persons with a dispensation of zanamivir recorded between October 1, 1999, and April 30, 2000. We captured medical and pharmaceutical claims data for the 6 months before the dispensation to obtain information about comorbidities, overall health status, and respiratory events. Medical and hospital record abstraction and clinical review served to confirm inpatient/emergency department (ED) events. We also examined the records of an ∼ 10% random sample of patients treated for a potential respiratory event in an outpatient/physician office visit during the 10-day follow-up period. Respiratory events not sufficiently severe to result in medical care were not captured in this study.Results: A total of 5498 eligible zanamivir dispensations contributed by 5450 patients (2911 females, 2539 males; mean age, 38.8 years), with 40 confirmed inpatient/ED respiratory events, were included in the study. Of these 40 events, 31 were pneumonia, bronchitis, or exacerbations of existing chronic respiratory disease; none required intubation or ventilation. No events occurred on the dispensation date. The overall risk for an inpatient/ED respiratory event was 0.7 per 100 episodes (95% CI, 0.5–1.0). Seven events of wheezing or shortness of breath were not an obvious extension of the original influenza-like illness or of a complicating bronchitis (risk = 0.13 per 100 episodes; 95% CI, 0.06–0.26).Conclusions: No immediate or severe bronchoconstrictive responses occurred among 5498 zanamivir dispensations. The overall risk for any respiratory event was low, and none was sufficiently severe to suggest respiratory failure. [Copyright &y& Elsevier]