Pharmacokinetics of azithromycin in serum and sinus fluid after administration of extended-release and immediate-release formulations in patients with acute bacterial sinusitis.

As high drug levels at the infection site are desirable for optimal activity, this study explored whether one dose of azithromycin extended release (AZ-ER) achieved higher azithromycin exposure in sinus fluid than azithromycin immediate release (AZ-IR) in adults with acute bacterial sinusitis. Subjects received AZ-ER (2g single dose; n=5) or AZ-IR (500mg daily for 3 days; n=4) and blood and sinus aspirates were collected until 120 h after initial dosing. Within 24 h, exposure was four- and three-fold higher with AZ-ER than with AZ-IR in serum and sinus fluid, respectively. Sinus fluid exposure was five- and three-fold higher than serum for AZ-IR and AZ-ER, respectively. Azithromycin concentrations in sinus fluid were maintained up to 120 h.