title: Comparative pharmacokinetics of azithromycin in serum and white blood cells of healthy subjects receiving a single-dose extended-release regimen versus a 3-day immediate-release regimen.
abstract: The pharmacokinetic profiles of azithromycin given as a single-dose regimen (2.0-g extended-release microspheres) were characterized in serum and white blood cells (WBC) and compared with those of a 3-day regimen (a 500-mg immediate-release tablet once daily; total dose, 1.5 g) in an open-label, randomized, parallel-group study of 24 healthy adult subjects. Serial blood samples were collected up to 5 days after the start of dosing for both regimens. Safety assessments were conducted throughout the study. A single 2.0-g dose of azithromycin microspheres achieved significantly higher exposures in serum and WBC during the first 24 h after the start of dosing than a 3-day regimen: an approximately threefold higher area under the curve from time zero to 24 h postdose (AUC(0-24)) and an approximately twofold higher mean peak concentration on day 1. The single-dose regimen provided total azithromycin exposures in serum and WBC similar to those of the 3-day regimen, as evidenced by the similar AUC(0-120) and trough azithromycin concentrations in serum and WBC (mononuclear leukocytes [MNL] and polymorphonuclear leukocytes [PMNL]). For both regimens, the average total azithromycin exposures in MNL and PMNL were approximately 300- and 600-fold higher than those in serum. Azithromycin concentrations in MNL and PMNL remained above 10 microg/ml for at least 5 days after the start of dosing for both regimens. This "front-loading" of the dose on day 1 is safely achieved by the extended-release microsphere formulation, which maximizes the drug exposure at the time when the bacterial burden is likely to be highest.
authors.affiliation: Department of Clinical Pharmacology, Pfizer Global Research and Development, 50 Pequot Ave., New London, CT 06320, USA.
authors.forename: Ping
authors.initials: P
authors.lastname: Liu
authors.forename: Hameed
authors.initials: H
authors.lastname: Allaudeen
authors.forename: Richa
authors.initials: R
authors.lastname: Chandra
authors.forename: Kem
authors.initials: K
authors.lastname: Phillips
authors.forename: Arvid
authors.initials: A
authors.lastname: Jungnik
authors.forename: Jeanne D
authors.initials: JD
authors.lastname: Breen
authors.forename: Amarnath
authors.initials: A
authors.lastname: Sharma
mesh_terms: D000293:Adolescent; D000328:Adult; D000900:Anti-Bacterial Agents / Q000008:administration & dosage / Q000493:pharmacokinetics*; D019540:Area Under Curve; D017963:Azithromycin / Q000008:administration & dosage / Q000493:pharmacokinetics*; D003692:Delayed-Action Preparations / Q000008:administration & dosage / Q000493:pharmacokinetics*; D005260:Female; D006801:Humans; D007962:Leukocytes / Q000378:metabolism*; D007963:Leukocytes, Mononuclear / Q000378:metabolism; D008297:Male; D009504:Neutrophils / Q000378:metabolism; D044967:Serum / Q000378:metabolism*
chemical_list: D000900:Anti-Bacterial Agents; D003692:Delayed-Action Preparations; D017963:Azithromycin