Impact of zanamivir on antibiotic use for respiratory events following acute influenza in adolescents and adults.
BACKGROUND
Influenza infections commonly lead to respiratory tract complications that result in antibiotic treatment.


OBJECTIVE
To determine frequency of respiratory events leading to antibiotic use following influenza illness in adolescents and adults, and to assess whether treatment with topical zanamivir prevents these complications.


METHODS
Meta-analysis of 7 randomized, double-blind, placebo-controlled trials; 3815 mainly healthy adolescents and adults (mean age, 34 years) with an influenzalike illness of less than 2 days' duration were randomly assigned to receive combined inhaled and intranasal zanamivir, inhaled zanamivir, or corresponding placebos. Twelve percent of enrolled subjects were high-risk patients. The main outcome was the incidence of respiratory events leading to antibiotic prescriptions in patients with proven influenza.


RESULTS
Influenza infections were laboratory confirmed in 2499 (66%) of 3815 patients (influenza A in 88% and B in 12%). Placebo recipients developed a respiratory event leading to antibiotic use in 17% of cases, mainly for acute bronchitis or acute sinusitis. Among zanamivir-treated patients (n = 1494) the incidence of respiratory events leading to the use of antimicrobials was 11% (relative risk [RR] compared with placebo, 0.69; 95% confidence interval [CI], 0.57-0.84). Intranasal and inhaled zanamivir seemed to reduce the number of upper (RR, 0.59; 95% CI, 0.36-0.97) and lower respiratory tract events (RR, 0.64; 95% CI, 0.38-1.08). Inhaled zanamivir reduced the number of lower respiratory tract events (RR, 0.60; 95% CI, 0.42-0.85), but the reduction in the number of upper respiratory tract events was not statistically significant (RR, 0.90; 95% CI, 0.63-1.27).


CONCLUSIONS
Respiratory complications or worsening of symptoms leading to antibiotic use occurred in about 17% of adolescents or adults with influenza infection. Early treatment of influenza illness with zanamivir reduced the number of these antibiotic prescriptions. Arch Intern Med. 2000;160:3234-3240.
Kaiser
L
L
University of Virginia School of Medicine, Department of Internal Medicine, Division of Epidemiology and Virology, Box 800473, Charlottesville, VA 22908, USA. laurent.kaiser@hcuge.ch
Keene
O N
ON
Hammond
J M
JM
Elliott
M
M
Hayden
F G
FG
D000208:Acute Disease; D000280:Administration, Inhalation; D000281:Administration, Intranasal; D000293:Adolescent; D000328:Adult; D000368:Aged; D000900:Anti-Bacterial Agents / Q000008:administration & dosage*; D000998:Antiviral Agents / Q000008:administration & dosage / Q000627:therapeutic use*; D017322:Clinical Trials, Phase II as Topic; D017326:Clinical Trials, Phase III as Topic; D004311:Double-Blind Method; D011307:Drug Prescriptions / Q000706:statistics & numerical data; D006146:Guanidines; D006801:Humans; D015994:Incidence; D007251:Influenza, Human / Q000150:complications* / Q000188:drug therapy*; D008875:Middle Aged; D015337:Multicenter Studies as Topic; D011714:Pyrans; D016032:Randomized Controlled Trials as Topic; D012141:Respiratory Tract Infections / Q000188:drug therapy / Q000517:prevention & control* / Q000821:virology*; D012307:Risk Factors; D012794:Sialic Acids / Q000008:administration & dosage / Q000627:therapeutic use*; D013997:Time Factors; D016896:Treatment Outcome; D053243:Zanamivir
D000900:Anti-Bacterial Agents; D000998:Antiviral Agents; D006146:Guanidines; D011714:Pyrans; D012794:Sialic Acids; D053243:Zanamivir