Pfizer Inc said that the US Food and Drug Administration has approved Zithromax (azithromycin) as a once-daily, three-day treatment for acute bacterial sinusitis (ABS). Zithromax is the only antibiotic approved as a three-day treatment regimen for acute bacterial sinusitis.

Most antibiotics commonly prescribed for ABS require 7 to 14 days of multi-dose therapy. Zithromax has unique attributes, including high and sustained drug levels in infected tissues that make a shortened dosing regimen possible.

"Zithromax administered once-a-day for three days represents a breakthrough for physicians in treating acute bacterial sinusitis," said Joseph Feczko, MD, president Worldwide Development. "The dosing regimen offers an efficacious treatment option that may help patients complete the course of treatment."

ABS is an acute infection of the sinuses most often caused by the pathogens strepococcus pneumoniae, haemophilus influenzae or moraxella catarrhalis. Symptoms include nasal discharge, nasal congestion, fever and facial pain or tenderness. Symptoms of untreated ABS generally last longer than 10 days and perhaps as long as three months. Approximately 20 million Americans develop ABS annually, resulting in an estimated 25 million physician visits and associated healthcare costs of up to $6 billion.

In one randomized, double-blind controlled study, Zithromax 500 mg once daily for three days was compared with the antibiotic Augmentin (amoxicillin/clavulanate) 500/125mg three-times daily for 10 days. Clinical efficacy for the three-day dosage of Zithromax was comparable to 10 days of Augmentin. Furthermore, 99 per cent of patients taking Zithromax once-daily for three days completed the course of therapy versus 82 per cent for the comparator.

Fewer patients receiving Zithromax reported treatment-related side effects than those receiving Augmentin. The most common treatment-related side effects in this study were diarrhea (Zithromax, 17 per cent; Augmentin, 32 per cent) and nausea (7 per cent and 12 per cent, respectively). The discontinuation rate due to adverse events was lower for three-day Zithromax, 2.2 per cent, than for Augmentin, 8.9 per cent.

Zithromax should not be taken by patients with hypersensitivity to azithromycin, erythromycin or any macrolide antibiotic. Antibiotic treatment should only be used for those infections caused by bacteria and only a health care provider can decide if antibiotic therapy is appropriate.

Developed and marketed by Pfizer, Zithromax was first approved in the US in 1992 for adults as the first once-daily, five-day oral antibiotic treatment of community-acquired respiratory infections and skin infections. In 1995, Zithromax was approved as a once-daily, five-day treatment for use in children with acute otitis media. In December 2001, Zithromax received FDA approval as both a single-dose regimen and three-day regimen for the treatment of acute otitis media in pediatric patients.