A Bioequivalence Study With Pharmacokinetic Endpoints for Azithromycin Eye Drops

Abstract Azithromycin eye drops with a bioadhesive ocular drug‐delivery system can offer a simplified dosing regimen. In this study, we compared the pharmacokinetic properties and assessed the bioequivalence of a newly developed generic azithromycin eye drop with a branded formulation. This open‐label, single‐dose, randomized, crossover, sparse‐sampling ocular bioequivalence study was conducted on 48 healthy Chinese volunteers. Tear samples were collected for up to 36 hours, and each participant was randomly allocated to one of the prespecified sampling times. Tear drug concentrations were determined using a validated liquid chromatography‐tandem mass spectrometry method. The pharmacokinetic parameters were calculated via noncompartmental analysis. A nonparametric bootstrap method was used to obtain 90% confidence intervals (CIs) for the ratios of the test and reference drugs. Tolerability was evaluated for adverse events (AEs). After bootstrapping (1000 iterations), the 90%CIs for the log‐transformed ratios of C max , AUC 0‐t , and AUC 0–∞ were within the acceptable bioequivalence range (80%–125%). No moderate‐to‐severe AEs were reported for either formulation. Bioequivalence was demonstrated between the two formulations. The sparse‐sampling design with the bootstrapping technique is promising for bioequivalence studies of topical ophthalmic drugs.