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J Clin Pharm Ther. 2005 Jun;30(3):251-4.

Cost considerations of the new fixed combinations for glaucoma medical therapy.

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Department of Ophthalmology, McGill University Health Center, Montreal, Quebec, Canada.



To compare the costs of the new fixed combinations for glaucoma medical therapy.


The studied drugs were: Cosopt (5-mL bottle), Combigan (5-mL bottle) and Xalacom (2.5-mL bottle). Five bottles of each drug were obtained from pharmacies, and the medications lot numbers were recorded. To calculate the drop volume, 10 drops and 1 mL of each bottle were weighed with a digital precision scale. Drop volume was calculated by the relation between volume and weight. The cost of each bottle of medication was determined from the average retail price in Canada. The prices were obtained in Canadian dollars (dollars).


The drops of Cosopt (39.60 +/- 0.45 microL) were considerably larger than the drops of Combigan (33.75 +/- 0.60 microL) and Xalacom (30.87 +/- 0.37 microL). The average number of drops per millilitre varied from 25.25 +/- 0.29 (Cosopt) to 32.40 +/- 0.39 microL (Xalacom). Combigan presented the lowest daily cost (dollars 0.87 +/- 0.02) followed by Xalacom (dollars 1.09 +/- 0.01) and Cosopt (dollars 1.22 +/- 0.01). The average cost by year varied from dollars 316.75 +/- 5.59 (Combigan) to dollars 445.96 +/- 5.16 (Cosopt), with a total difference of dollars 129.21 per year of treatment.


There was a statistically significant difference in average drop size and cost among the three studied drugs. Combigan presented the lowest daily cost followed by Xalacom and Cosopt.

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