A Comparison of the Settling and Particle Size Characteristics for T-PredTM, Tobradex®, and ZyletTM Ophthalmic Suspensions

Abstract

Purpose:: To compare the settling and particle size characteristics of ophthalmic suspensions; T-Pred^TM (prednisolone acetate 1.0% and tobramycin 0.3%, pending FDA approval), Tobradex^® (dexamethasone 0.1% and tobramycin 0.3%), and Zylet^TM (loteprednol etabonate 0.5% and tobramycin 0.3%).

Methods:: The particle size of all three suspension products was measured using a Beckman Coulter LS 13 320 particle size analyzer equipped with a universal liquid module. Particle size measurements were taken before and after sonication to break up any aggregates. Settling rates for all three products were compared by dispensing into test tubes and vortexing, followed by visual inspection and photo-documentation periodically for 24-hours.

Results:: T-Pred^TM exhibited a tighter particle size distribution and a smaller average particle size than either Zylet^TM or Tobradex^®. The mean particle size for T-Pred^TM, Zylet^TM, and Tobradex^® before sonication was 1.2 µm, 3.5 µm, and 2.4 µm respectively and 0.6 µm, 2.4 µm, and 2.4 µm respectively after sonication. Over a period of 24-hours, T-Pred^TM also exhibited slower settling rates compared to the other two products.

Conclusions:: T-Pred^TM exhibited a tighter particle size distribution and a smaller average particle size than either Zylet^TM or Tobradex^®. When compared to either Zylet^TM or Tobradex^®, T-Pred^TM also demonstrated substantially less settling.

Keywords: antibiotics/antifungals/antiparasitics • corticosteroids • inflammation