Efficiency of instillation methods for prostaglandin medications

The aim of this study was to determine the most efficient methods for instillation of prostaglandin analogs.

Drops were dispensed at room temperature from 2.5-mL bottles of bimatoprost, travoprost, and latanoprost. Two determinations of drop count were each made from bottles held vertically, at a 45-degree angle, and horizontally. The total volumes of medication dispensed from each bottle were measured.

The mean number of drops dispensed was 111.0, 105.1, and 76.1 drops for bimatoprost bottles; 81.4, 101.1, and 85.3 drops for travoprost bottles; and 94.3, 88.4, and 67.1 drops for latanoprost bottles, held vertically, at 45 degrees, and horizontally, respectively. The mean volume of medication dispensed per 2.5-mL bottle was 3.17 mL for bimatoprost, 2.54 mL for travoprost, and 3.02 mL for latanoprost. The most efficient instillation methods provided 56 days of bilateral therapy per 2.5-mL bottle for bimatoprost, 51 days for travoprost, and 47 days for latanoprost, with corresponding yearly medication costs of $408 for bimatoprost, $449 for travoprost, and $475 for latanoprost. Yearly savings of $109 to $192 could be achieved by using the most efficient instillation methods, representing 5.6 months of medication saved for patients using bimatoprost, 3.0 months for patients using travoprost, and 4.9 months for patients using latanoprost.

Health care providers are urged to instruct glaucoma patients in the most efficient method of instillation. For bimatoprost and latanoprost, vertical instillation is recommended, with 45 degrees nearly as efficient, and for travoprost, instillation at 45 degrees is recommended.