New Study Confirms Superiority of Augmentin to Zithromax in Treating Middle Ear Infections

February 02, 2000

New York (MedscapeWire) Feb 2 -- Augmentin (amoxicillin/clavulanate), an oral antibiotic, is more effective than Zithromax (azithromycin) in eradicating the most common bacteria that cause middle ear infections (acute otitis media, or AOM) in children, according to a new study published in the February issue of the Pediatric Infectious Disease Journal. The study also shows that Augmentin is more effective in reducing or curing the symptoms associated with AOM.

"Because we have entered this era of drug resistance, physicians should select an antibiotic based on its ability to eradicate the infecting organism, not duration of therapy, convenience or taste," said clinical investigator Candice Johnson, MD, of The Children's Hospital of Denver. "This study showed that a ten-day course of Augmentin was significantly more effective in killing bacteria and improving symptoms than a five-day course of Zithromax."

According to the Centers for Disease Control and Prevention (CDC), the bacteria Haemophilus influenzae and Streptococcus pneumoniae combined account for more than 70% of all middle ear infections. These bacteria are becoming increasingly resistant to antibiotics, with S. pneumoniae and H. influenzae resistance approaching 50% and 42% in the United States, respectively. A child with an ear infection caused by a resistant organism is at risk for developing a more serious illness, such as mastoiditis (a severe infection and swelling of the mastoid bone, which is located behind the ear), if effective antibiotics are not used. These study results support the most recent CDC treatment recommendations for AOM, which cite Augmentin as 1 of 3 oral agents recommended for the treatment of this condition. The CDC does not include Zithromax in its treatment recommendations.

Next to the common cold, ear infections are the most common childhood illness and are responsible for more than 30 million doctor visits each year. Three of every four children experience at least 1 episode of otitis media before the age of 3 years, and almost half of these children have 3 or more episodes before the age of 3 years. Some temporary hearing loss almost always accompanies fluid in the ear -- with or without infection. Therefore, chronic ear infections can reduce a child's hearing during a time that is critical for speech and language development. Additionally, on rare occasions an ear infection, if poorly treated, may lead to a ruptured eardrum, felt as a sharp pain and popping sensation, followed by fluid draining out of the ear. If a child has more than 3 or 4 ear infections per year or has a hearing loss due to persistent fluid for more than 6 months, it is often necessary for tubes to be surgically implanted into the child's ears to treat the infection.

This is the first study comparing Augmentin with Zithromax to measure bacterial eradication (actual killing of the bacteria), as measured by a "double tap" -- also known as double tympanocentesis. This testing method involves culturing middle ear fluid, and most experts consider it to be a more rigorous test of antibiotic efficacy than measurement of symptomatic improvement alone.

In this multicenter, randomized trial involving 238 children between the ages of 6 months to 2 years with AOM, participants received typical US doses of Augmentin (45 mg/kg/day in 2 divided doses for 10 days) or Zithromax (10 mg/kg on day 1 followed by 5 mg/kg every 24 hours on days 2 through 5). At baseline, cultures were obtained from the middle ear fluid of all participants using a tympanocentesis. The fluid was tested for the presence of H. influenzae, S. pneumoniae, and other pathogens. In children with an initial positive bacterial culture, an additional culture was obtained on days 4, 5, or 6, and tested to determine whether the antibiotic they received had successfully eradicated the infecting bacteria.

Analysis showed that Augmeeentin was significantly superior to Zithromax in eradicating all bacterial pathogens (83% vs 49%). Specifically, Augmentin eradicated 87% of H. influenzae vs 39% for Zithromax, a statistically significant difference, and 90% of S. pneumoniae bacteria compared with 68% for Zithromax. Augmentin, which contains a substance called clavulanate potassium, is specifically designed to inhibit beta-lactamase, an enzyme produced by certain bacteria that can render many antibiotics ineffective.

Augmentin was also significantly more effective in terms of clinical outcomes, overall "curing" (complete resolution of) or "improving" (lessening of) symptoms in 86% of patients vs 70% for Zithromax. More specifically, 90% of those infected with H. influenzae were considered either "cured" or "improved" at the end of the study compared with 63% of the patients treated with Zithromax.

"Augmentin's superior bacterial eradication not only leads to more rapid clinical improvement, but it is also an insurance policy against the serious complications of otitis media," added Dr. Johnson.

Both drugs in the study were well tolerated. The most commonly reported adverse experiences were vomiting, diarrhea, fever, and rash.

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