Chemical Analysis of Branded Latanoprost 0.005% Compared With Commercially Available Latanoprost Formulations

Abstract

Purpose: : To evaluate the composition of branded latanoprost (Xalatan) and its preservative with two commercially available generic formulations.

Methods: : Reference solutions of latanoprost and BAK were prepared. High Performance Liquid Chromatography was performed on Xalatan and two different formulations of generic latanoprost, each advertised with a concentration of 0.005% latanoprost.

Results: : The mean concentrations of latanoprost found in Xalatan was 44.3 µg/mL (Variation = 2.0%), BAK 0.023% (Variation = 0.6%). The mean concentrations of latanoprost found in the two generic formulations were generic formulation #1: 43.0 µg/mL (Variation = 8.8%), BAK 0.023% (Variation = 2.6%) and generic formulation #2: 40.8 µg/mL (Variation = 7.8%), BAK 0.022% (Variation = 7.0%).

Conclusions: : Prior clinical studies have indicated a difference in efficacy between branded latanoprost and a generic preparation. Other prior studies have shown that the amount of available drug diminishes under stressful environmental situations. This may be due to the fact that latanoprost is a highly lipophilic molecule that is difficult to maintain at higher levels in aqueous solution. The current study demonstrates that there are differences in measurable drug and preservative present in the different formulations. A high degree of variability was also demonstrated among samples of the generic preparations.Variability and differences in concentration of latanoprost and preservative exists among available formulations. Further studies are necessary to determine the clinical significance of this variability.

Keywords: intraocular pressure