One Time Only Hate taking medication? A new one-dose antibiotic said to cure respiratory infections could cut the usual multi-day antibiotic regimen to a single dose, according to drug maker Pfizer.

The unnamed drug is a form of azithromycin. If approved, it would be the first to cure such infections in one dose. That would be especially useful for the many patients who stop taking antibiotics when they feel better, said Jeanne DeMars Breen, Pfizer's senior director of infectious disease clinical research. Skipping even a few days of prescribed antibiotics can cause bacteria to resist some future treatments, Breen said. Pfizer submitted results of three trials to the Food and Drug Administration and hopes for approval sometime next year.

Back Story Pfizer makes Zithromax, a form of azithromycin that has been on the market since 1992. It comes in several variations: the Z-pak (a five-day course of pills), the Tri-pak (pills taken for three days), a liquid for children and an intravenous form for hospital patients. The patents on those formulations are due to expire in November 2005, according to Pfizer.

The Old, the New A Pfizer-funded study found that for patients with chronic bronchitis with underlying lung infections, the new one-dose form of azithromycin was nearly as effective as Levaquin, a commonly prescribed antibiotic taken for seven days. In another trial, sinusitis patients taking the new drug fared slightly better than those on a 10-day Levaquin regimen. A third study found the new drug as effective as a typical treatment in patients with mild to moderate pneumonia.

Doctor's Orders The new medication comes in liquid form, Breen said; adult dosage is three to five tablespoons. Despite its kid-friendly form, the drug has not been studied for use in children.

-- January W. Payne