Clinical toleration and safety of azithromycin.

The toleration and safety profile of the azalide antibiotic, azithromycin, has been assessed in 3,995 patients aged 2-94 (mean, 36) years, comprising 1,644 females and 2,351 males. Patients with infections of the respiratory tract or skin/skin structure received 1.5 g azithromycin over 5 days; patients with urethritis/cervicitis caused by Chlamydia were treated with 1 g as a single dose. Assessments of side effects and laboratory safety test abnormalities were made pretreatment and approximately 7-14 and 30 days after the start of therapy. Twelve standard antibiotics have been used for comparison. Overall, side effects were recorded in 12.0% of patients, significantly less (p less than 0.05) than with comparative drugs (14.2%). The most common side effects were diarrhea (3.6%), abdominal pain (2.5%), and other gastrointestinal symptoms. Ninety-three percent of side effects were classed as mild or moderate, and only 0.7% of patients withdrew from treatment, significantly less (p less than 0.001) than with comparative agents (2.6%). The frequency of side effects was not affected by patient age. Azithromycin had no marked or consistent effect on laboratory safety parameters. Treatment-related laboratory abnormalities were rare, the most common being transient increases of ALT and AST in 1.7% and 1.5% of patients, respectively. Specific tests revealed no neurologic, audiometric, or ophthalmologic abnormalities, or evidence of phospholipidosis. There were no pharmacokinetic interactions observed with theophylline, warfarin, cimetidine, carbamazepine, or methylprednisolone, but coadministration with food altered the absorption of the drug. Coadministration with antacids decreased the peak serum concentration of azithromycin, but did not affect its overall absorption. Azithromycin was well tolerated in the presence of a wide variety of concurrent illnesses and medications.