WASHINGTON -- Three head-to-head studies
presented during the 44th annual Interscience Conference on Antimicrobial
Agents and Chemotherapy (ICAAC) in Washington show that Pfizer Inc.'s new
investigational microsphere formulation of azithromycin, which is dosed as a
one-time-only oral antibiotic, is comparable to other frequently prescribed
treatments for some of the most common respiratory tract infections in adult
patients. Azithromycin has been available in the United States since 1992
under the tradename Zithromax.
Pfizer sponsored the studies and has
submitted the data for review by the Food and Drug Administration (FDA). The
Company is seeking approval for the treatment of adult respiratory tract
infections, including acute bacterial exacerbations of chronic bronchitis
(AECB) acute bacterial sinusitis (ABS) and community acquired pneumonia (CAP).
These three studies showed that with one dose, azithromycin microspheres
provides a complete course of therapy for the treatment of AECB, ABS and CAP.
Azithromycin microspheres was compared to a seven-day regimen of
clarithromycin XL for the treatment of CAP and to seven- and 10-day courses
of levofloxacin for the treatment of AECB and ABS, respectively.
"Given the efficacy of a one-time-dose for these common infections and the
assured compliance, the hope would be that this type of regimen can help
minimize the emergence of antibiotic resistance," said Michael Niederman,
MD, chairman of the Department of Medicine at Winthrop-University Hospital,
Mineola, N.Y. and professor of medicine at the State University of New York at
Stony Brook. "Antibiotic resistance is a growing problem in the treatment of
community respiratory tract infections, and one of the factors that
contributes to its development is patients taking an incomplete course of
In two of three multicenter, randomized, double-blind, double-dummy trials
presented, azithromycin microspheres was compared to levofloxacin. One study
examined azithromycin microspheres (2.0 g) and levofloxacin (500 mg/day for
seven days) in 446 subjects with AECB. The clinical cure rate in the
azithromycin microspheres group was comparable (95 percent) to the
levofloxacin group (96 percent). Chronic bronchitis is characterized by
excessive cough and sputum production on most days for at least three months
during at least two consecutive years with intermittent acute exacerbations.
AECB are usually manifested as an increase in dyspnea (difficult or labored
breathing), sputum volume and/or sputum purulence (pus).(1)
Azithromycin microspheres was also compared to levofloxacin (500 mg/day
for 10 days) in 541 patients with ABS. Clinical success rates were
comparable -- 94.5 percent of patients treated with azithromycin microspheres
and 92.8 percent of levofloxacin-treated patients. ABS is an acute infection
of the sinuses that can cause purulent nasal discharge, nasal congestion,
fever and facial pain or tenderness(2).
In another study presented during the meeting, the new formulation of
azithromycin was compared to clarithromycin XL (1 g/day for seven days) in 501
randomized subjects with mild-to-moderate CAP. Treatment with azithromycin
microspheres resulted in comparable pathogen eradication rates (91.8 percent)
vs. clarithromycin XL (90.5 percent). The clinical success rate in the
azithromycin microspheres group was 92.6 percent vs. 94.7 percent in the
clarithromycin XL group. CAP is a lung infection acquired outside of
hospitals or extended-care facilities.(3)
"A one-dose-only treatment is a significant advance, giving physicians and
patients an option that can effectively treat the most common respiratory
tract infections that occur in adults, while also providing an additional
benefit regarding noncompliance with therapy," said Joseph Feczko, MD,
president of Worldwide Development, Pfizer Inc.
The new formulation of azithromycin microspheres offers a safety profile
comparable to other antibiotic treatments for common respiratory tract
infections and is generally well tolerated. In clinical studies, side effects
were generally mild and resolved within two days for the majority of patients.
The most common adverse events on day one were diarrhea/loose stools
(11.7 percent), nausea (3.9 percent), abdominal pain (2.7 percent) and
vomiting (1.1 percent).(4) Patients with known hypersensitivity to
azithromycin, erythromycin or any macrolide or ketolide antibiotic should not
take azithromycin microspheres.
The new azithromycin formulation allows for delayed release of drug, which
occurs in the small intestine instead of in the stomach, maintaining
tolerability. This, together with the long half-life of azithromycin
microspheres, makes it possible to deliver the entire two-gram dose as a
single dose regimen.
Pfizer Inc. discovers, develops, manufactures and markets leading
prescription medicines for humans and animals and many of the world's best-
known consumer brands.
(1) Niederman, Michael S. "Nationalise: North American Taskforce on
Improving Outcomes in AECB and LRTIs - Implementation, Strategies and
Education." Supplement to Consultant. Oct 2002, Vol 42, Num 12, pgs.
(2) Piccirillo JF. "Acute Bacterial Sinusitis." New England Journal of
Medicine. 2004; 351:902-910. Number 9
(3) Schmitt SK. "Community-Acquired Pneumonia." The Cleveland Clinic
(4) Pfizer product insert: Azithromycin microspheres.
Source: Pfizer, Inc