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Generic versus brand-name North American topical glaucoma drops

      Abstract

      Objective

      To determine whether brand-name glaucoma drops differ from generic equivalents in bottle design, viscosity, surface tension, and volume in North America.

      Design

      Experimental study.

      Participants

      We studied 5 bottles each of 11 kinds of glaucoma drops.

      Methods

      Density-based calculations of drop volume were assessed using 0.1 mg analytic balance. Viscosity was measured using rotational rheometery. Bottle tip diameter was measured using 0.05 mm Vernier calipers. Surface tension was measured using a Fisher Scientific (Ottawa, ON) tensiometer.

      Results

      For the American brand-name Timoptic XE, the average drop volume was 38 ± 3.1 μL versus 24 ± 1.5 μL of Timolol GFS (p < 0.0001). For the Canadian brand-name Timoptic XE, the average drop volume was 42 ± 4.0 μL versus 25 ± 2 μL of timolol maleate EX (p < 0.0001). The Canadian brand-name Timoptic drop volume was 28 ± 1.4 μL versus 35 ± 1.9 μL Apo-Timop (p < 0.01). At a 0.1 per second shear rate, the viscosity of Canadian Timoptic XE was 20 times higher than that of its generic equivalent, whereas the viscosity of American Timoptic XE differed from the generic by a factor of 100. The surface tension of Canadian Timoptic XE was 31% higher than that of the generic (p < 0.001), whereas the surface tension of American Timoptic XE was 21% higher than that of the generic (p < 0.001). The bottle tips of the Canadian and American Timoptic XE measured about 3.5 times larger than those of their generics.

      Conclusion

      American and Canadian Timoptic XE eye drops vary significantly from the generics in drop volume, viscosity, surface tension, and bottle tip. Canadian brand-name Timoptic delivered significantly smaller drop volumes than generic Apo-Timop. Careful consideration should be given to drop viscosity and bottle design when generic ophthalmic products are evaluated for interchangeability and market entry.

      Résumé

      Objet

      Établir si les gouttes pour le glaucome portant une marque de commerce diffèrent des équivalents génériques quant à la conception des bouteilles, la viscosité, la tension de surface et le volume, en Amérique-du-Nord.

      Nature

      Étude expérimentale.

      Participants

      Nous étudions 5 bouteilles de 11 medicaments de glaucome.

      Méthodes

      Le calcul du volume des gouttes, fondé sur la densité, a été évalué à l'aide d'une balance analytique de 0,1 mg. La viscosité a été mesurée avec le rhéomètre en mode rotation. Le diamètre de l'embout des bouteilles a été mesuré avec un pied à coulisse de 0,05 mm. La tension de surface a été mesurée à l'aide d'un tensiomètre scientifique Fisher.

      Résultats

      Le volume moyen de la goutte portant la marque de commerce américaine Timoptic CE était de 38 ± 3.1 μL versus celui de 2 ± 1.5 μL du Timolol GFS (p < 0.0001). Le volume moyen de la goutte portant la marque de commerce canadienne Timoptic XE était de 42 ± 4 μL versus celui de 25 ± 2 μL du Timolol Maleate EX (p < 0.0001). Le volume des gouttes de la marque canadienne Timoptic était de 28 ± 1.4 μL versus celui de 35 ± 1.9 μL d'Apo-Timop (p < 0.01). À une vitesse de cisaillement de 0.1 seconde, la viscosité de la Timoptic XE canadienne était vingt fois supérieure à son équivalent générique alors que la viscosité de la Timoptic XE américaine différait du générique par un facteur de 100. La tension de surface de la Timoptic XE canadienne était plus élevée de 31% de celle du générique (p < 0.001) alors que la tension de surface de la Timoptic XE américaine était plus élevée de 21% de celle du générique (p < 0.001). L'embout des bouteilles de Timoptic XE canadiennes et américaines étaient environ 3,5 fois plus grand que celui des génériques.

      Conclusion

      Les gouttes oculaires Timoptic XE américaines et canadiennes varient grandement des génériques quant au volume des gouttes, à la viscosité, à la tension de surface, et à l'embout des bouteilles. La marque de commerce Timoptic a livré des volumes de goutte beaucoup plus petits que le générique Apo-Timop. Il faudrait examiner attentivement la viscosité des gouttes et la conception des bouteilles lors de l'évaluation des produits ophtalmiques pour l'interchangeabilité et l'entrée sur le marché.
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