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Antimicrobial Agents and Chemotherapy, August 2003, p. 2663-2665, Vol. 47, No. 8
0066-4804/03/$08.00+0 DOI: 10.1128/AAC.47.8.2663-2665.2003
Copyright © 2003, American Society for Microbiology. All Rights Reserved.
Pfizer Global Research & Development, New London, Connecticut,1 Maya Family Medical Center, Chicago, Illinois,2 Hospital Nacional de Niños and Neeman-ICIC, San Jose, Costa Rica,3 Hospital Infantil Juan Pablo II, Guatemala City, Guatemala,4 Children's Hospital of Orange County, Orange,5 Pediatrics Plus, Clovis,7 Children's Hospital and Health Center, San Diego, California,14 Scottsdale Pediatric Center, Scottsdale, Arizona,6 Primary Physicians Research,8 Center for Genomic Sciences, Allegheny Singer Research Institute and Department of Microbiology and Immunology, MCP Hahnemann School of Medicine, Pittsburgh, Pennsylvania,18 Vienna Pediatric Associates, Vienna, Virginia,9 Clinical Research Group, University of Chile School of Medicine,10 Centro Médico OTOMED,11 Hospital Clinico Universidad de Chile,12 Hospital Luis Calvo Mackenna, Santiago, Chile,16 Hill Top Research, Inc., Salt Lake City, Utah,13 University of North Texas Health Science Center at Ft. Worth, Department of Pediatrics, Ft. Worth, Texas,15 Rainbow Babies and Children's Hospital, Cleveland, Ohio,17 Pfizer, Inc., New York, New York,19
Received 25 November 2002/ Returned for modification 17 February 2003/ Accepted 7 May 2003
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Children were eligible for enrollment if they demonstrated one or more signs or symptoms of acute otitis media, including ear pain or fullness, discharge from the external auditory canal, decreased hearing, or fever. They must also have had one or more of the following: bulging or marked erythema of the tympanic membrane, loss of the normal light reflex or tympanic membrane landmarks, or impaired tympanic mobility on biphasic pneumatic otoscopy. The effusion was to be documented by acoustic reflectometry (8) with an abnormal reading of 3 or higher. Patients were excluded if they had a history of hypersensitivity to macrolides or azithromycin, had been treated with antibiotics in the previous 30 days, had symptoms of otitis media for longer than 4 weeks, had tympanostomy tubes present, or had been receiving antimicrobial prophylaxis. The institutional review board of each participating center reviewed and approved participation in the trial. Written informed consent was obtained for each patient.
Samples of middle ear fluid were obtained either by tympanocentesis or, in the case of a perforated tympanic membrane, with a swab. Patients then received 30 mg of azithromycin/kg in a single oral dose. Children who vomited within 30 min of dosing were redosed.
The samples of middle ear fluid were split for storage at a central laboratory and cultured locally. All pathogens isolated locally were subcultured and sent to a central laboratory (MDS Clinical Trial Laboratories) for confirmation and susceptibility testing. Phone contact with each patient occurred on study day 5 for assessment of adverse events; this was followed by visits on days 10 and 24 to 28, at which time detailed clinical assessments regarding clinical cure (complete resolution of all signs and symptoms of acute otitis media), improvement, or failure were made. Any patient who was considered to have failed therapy was to have a repeat tympanocentesis.
The final sample size was achieved by allowing for sufficient enrollment to accrue at least 25 patients with Streptococcus pneumoniae, 25 with Haemophilus influenzae, and 15 with Moraxella catarrhalis in the fluid samples from the baseline tympanocenteses. The primary endpoint of the trial was the investigator-designated cure rate at days 24 to 28, for which a 95% confidence interval (CI) was computed using the normal approximation to the binomial distribution. Other endpoints analyzed included the clinical response rate by baseline pathogen at days 24 to 28 and the overall clinical response at day 10. Only S. pneumoniae, M. catarrhalis, and H. influenzae were considered baseline pathogens for the purposes of these analyses.
A total of 248 patients, of whom 247 received azithromycin, were entered in the trial between December 1999 and May 2000. Children from 22 sites distributed among the United States (63%), Costa Rica (16%), Guatemala (13%), and Chile (8%) were enrolled. The mean age of the children was 3.4 years (range, 6 months to 12 years), and 86 of 247 (35%) were
2 years of age. At the baseline tympanocentesis, 95% had evidence of bulging, decreased mobility, or erythema of the tympanic membrane and 89% had all three signs. Children under 2 years of age were more likely than those older than 2 years to have these signs, including fever (53 versus 36%, respectively) and impaired mobility of the tympanic membrane (98 versus 91%, respectively). Seventy-two percent (178 of 248) of the children were noted to have had previous episodes of otitis media. The mean duration of symptoms related to the present episode of acute otitis media was 2.5 days.
The clinical cure rate, as determined by investigator, at days 24 to 28 was 206 of 242 (85%) patients (Table 1). Children 2 years of age or younger had a lower cure rate (64 of 83; 77%) than children older than 2 years (142 of 159; 89%). Similar results were seen at day 10, with an overall success rate (cure plus improvement) of 89% (213 of 240 patients). A total of 124 patients had a pathogen identified at the baseline tympanocentesis. The clinical cure rate at days 24 to 28 for these subjects was 100 of 124 (81%). Cure rates were highest for patients with M. catarrhalis isolated at baseline (10 of 10; 100%), followed by S. pneumoniae (67 of 76; 88%) and H. influenzae (28 of 44; 64%). At day 10, the clinical success rate for patients with a pathogen identified at baseline was 86% (105 of 122). By baseline pathogen, the success rates at day 10 were as follows: for M. catarrhalis, 10 of 10 patients (100%); for S. pneumoniae, 70 of 76 (92%); and for H. influenzae, 30 of 42 (71%). Ten children received another antibiotic because of an insufficient clinical response prior to day 5, resulting in a success rate of 96% up to that time point. Of these 10 failures, 5 had positive cultures identified at the baseline tympanocenteses, including 3 with H. influenzae infections, 1 with an S. pneumoniae infection, and 1 with a dual infection with S. pneumoniae and H. influenzae.
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TABLE 1. Clinical outcomes with azithromycin treatment by age range and baseline pathogen
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Twelve children were identified as having infections with macrolide-resistant S. pneumoniae isolates (Fig. 1). For 5 of the 12 isolates, the azithromycin MIC was >256 µg/ml, and all 12 were resistant to clindamycin; on PCR they were found to contain the erm(B) gene (11, 12). Only two of the five patients infected with these isolates were cured at day 28. For the seven remaining isolates, the azithromycin MIC was 8 µg/ml; these isolates were sensitive to clindamycin and were found to contain the mef(A) gene. Six of the seven children infected with these isolates were considered cured at day 28. Six of nine children with isolates of S. pneumoniae that were resistant to penicillin (MIC,
2 µg/ml) were cured at day 28. The three children who failed therapy were infected with isolates for which the macrolide MIC was >256 µg/ml; these isolates contained the erm(B) gene. All H. influenzae and M. catarrhalis strains that were isolated were susceptible to azithromycin.
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FIG. 1. Day 28 outcomes and MIC distributions for S. pneumoniae.
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As reported by the investigators, 30 of 248 (12.1%) subjects had adverse events that were possibly or probably related to azithromycin, with vomiting (6%) and diarrhea (3%) being the most common. One subject (0.4%) who vomited within 30 min of dosing was removed from therapy.
Azithromycin given in a single oral dose of 30 mg/kg of body weight resulted in clinical cure rates in this study that are consistent with those observed after a similar total dose was given over 5 days (1, 7, 9, 10) or over 3 days (M. W. Dunne, T. Latiolais, B. Lewis, B. Pistorius, G. Bottenfeld, W. Moore, and A. Shemer, Abstr. 41st Intersci. Conf. Antimicrob. Agents Chemother., abstr. G-1532, 2001). Response rates at days 24 to 28 for patients with S. pneumoniae and M. catarrhalis infections were high, and that for patients infected with H. influenzae was consistent with other similarly designed clinical trials (A. Arguedas, C. Loaiza, A. Perez, and A. Gutierrez, Abstr. 4th Int. Conf. Macrolides, Azalides, Streptogramins, Ketolides, abstr. 6.10, 1998; 2, 4, 6) (Table 2). The amount of drug delivered in the first 24 h is greater with a single-dose regimen than with either the 3-day or 5-day treatment options. While the contribution of the maximum concentration of drug in serum cannot be excluded (5), it is felt that the outcome is likely to be best predicted by the ratio of the AUC from 0 to 24 h to the MIC for the pathogen (3), supporting the overall comparability of these results to those of the 3-and 5-day regimens. Of particular interest was the efficacy in six of seven patients whose S. pneumoniae isolates were found to contain the mef(A) gene, which is responsible for efflux-mediated resistance. The possibility that efflux pump resistance could be overcome by exposing resistant organisms to higher concentrations of a drug earlier in the course of therapy warrants further evaluation.
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TABLE 2. Clinical outcomes by baseline pathogens at days 21 to 35 in studies of acute otitis media
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This work was supported by Pfizer, Inc.
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