Risk for respiratory events in a cohort of patients receiving inhaled zanamivir: a retrospective study.
BACKGROUND
Inhaled zanamivir is indicated for treatment of uncomplicated acute illness due to influenza A and B viruses in patients aged > or = 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 approximately 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.
Loughlin
Jeanne E
JE
Epidemiology & Safety Research Division, Ingenix, Inc., Auburndale, Massachusetts 02466, USA. jloughlin@epidemiology.com
Alfredson
Tanya D
TD
Ajene
Anuli N
AN
Cole
J Alexander
JA
Cook
Suzanne E
SE
Rosenberg
Daniel M
DM
Walker
Alexander M
AM
D000280:Administration, Inhalation; D000293:Adolescent; D000328:Adult; D000368:Aged; D000998:Antiviral Agents / Q000009:adverse effects* / Q000627:therapeutic use; D001982:Bronchial Diseases / Q000139:chemically induced*; D002648:Child; D015331:Cohort Studies; D003251:Constriction, Pathologic / Q000139:chemically induced; D004636:Emergency Service, Hospital / Q000706:statistics & numerical data; D005260:Female; D006146:Guanidines; D006760:Hospitalization; D006801:Humans; D007251:Influenza, Human / Q000188:drug therapy*; D007344:Insurance Claim Reporting; D008297:Male; D008875:Middle Aged; D011714:Pyrans; D012189:Retrospective Studies; D012306:Risk; D012621:Seasons; D012794:Sialic Acids / Q000009:adverse effects* / Q000627:therapeutic use; D053243:Zanamivir
D000998:Antiviral Agents; D006146:Guanidines; D011714:Pyrans; D012794:Sialic Acids; D053243:Zanamivir