Original articleGeneric versus brand-name North American topical glaucoma drops
Section snippets
Methods
We purchased 11 representative ocular medications (5 brand-name and 6 generic) that were created to lower elevated IOP. They were purchased from 1 hospital pharmacy in Canada and 4 community pharmacies in the United States. The products were stored at room temperature, per the manufacturers' recommendations, in a locked and secured area in the research laboratory facility at Toronto Western Hospital. All products were at least 9 months away from their expiry date during the testing phase of the
Results
Figure 1 shows the average drop volumes of the brand-name and generic products. Most notably, the Canadian brand-name Timoptic XE drop volume was 42 ± 4.0 μL versus 25 ± 2.0 μL for the Canadian generic timolol maleate EX (p < 0.0001). The American brand-name Timoptic XE average drop volume was 38 ± 3.1 μL versus 24 ± 1.5 μL for the American generic Timolol GFS (p < 0.0001). The Canadian brand-name Timoptic drop volume was 28 ± 1.4 μL versus 35 ± 1.9 μL for the generic Canadian Apo-Timop (p <
Discussion
In this study, we report that brand-name versus generic drop volume variability was found among a limited subset of the investigated eye drops. The most notable difference was observed between the gel-based beta-blocker formulations in both Canadian and American products. Generic Timolol GFS (Falcon Pharmaceuticals) delivered approximately 37% less drop volume than brand-name Timoptic XE (Merck U.S.). Generic Timolol Maleate EX (Pharmascience) delivered approximately 40% less drop volume than
Conclusions
American- and Canadian-produced brand-name Timoptic XE drops vary significantly from their country-specific generic equivalents in drop volume, viscosity, surface tension, and bottle orifice diameter. Generic Timolol Maleate EX (Pharmascience) delivered 40% less drop volume, and the daily prescribed dosage compared with that of brand-name Timoptic XE (Merck, Canada). Similarly, generic Timolol GFS (Falcon Pharmaceuticals) delivered 37% less drop volume and daily therapeutic dosage compared to
Disclosure
The authors have no proprietary or commercial interest in any materials discussed in this article.
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