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Umaima Mulla, Kelvin Wong, Elizabeth Tanner, David Young, Alan P Rotchford, ; Squeezing generic latanoprost. Are they the same?. Invest. Ophthalmol. Vis. Sci. 2014;55(13):537.
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Generic Latanoprost is the most widely prescribed topical anti-glaucoma. 3.5 million bottles were dispensed in England in 2011. Patients may receive different bottle types and design every month depending on the pharmacy supplier. Some patients may find the use of different bottles difficult. The purpose of this study is to assess the force required to expel a single drop of Latanoprost from different generic bottles and its effects on patients during daily usage.
Three bottles of seven preparations of generic Latanoprost (Pfizer, Actavis, Beacon, Sandoz, Teva, Tubilux, and Zentiva) were tested. A 1kN load cell was positioned horizontally with an aluminium semi cylindrical loading head attached and connected to a Zwick-Roell 250 mechanical testing unit. The bottles were inverted and force applied to expel 10 individual drops from each bottle was measured. Maximum load applied (in Newtons) during the delivery of each drop was found using Zwick-Roell computer software analysis.
The mean force required was: Actavis 11.50N, Beacon 33.94N, Sandoz 15.99N, Teva 17.81N, Tubilux 19.29N, Xalatan 22.61N, Zentiva 18.82N. Using repeated measures nested general linear model analysis, this represents a statistical significance in the difference between force required from a Xalatan bottle and other manufacturers. (p<0.001).
The bottle requiring least force was Actavis (11.50N) and the most was Beacon (33.94N). A person’s normal grip force is 17.8-160N. This is reduced in elderly people, in neurological and rheumatoid conditions. Force required for some generic preparations was higher than the lower range of normal grip force, suggesting that patients with a weak grip force may have difficulty with expression of drops from these bottles. Bottles with lower force requirements may run out quickly due to over expression of drops. Ophthalmologists should therefore consider difficulties patients may have with differing bottle types of generic Latanoprost and prescribe accordingly.
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