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L Nally, TB Emory, DL Welch; Ocular Drying Associated With Oral Antihistamines (Loratadine) in the Normal Population - Effect on Tear Flow and Tear Volume as Measured by Fluorophotometry . Invest. Ophthalmol. Vis. Sci. 2002;43(13):92.
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Purpose:Anti-muscarinic activity is thought to be the cause of ocular dryness associated with antihistamine use. This study investigated the anti-muscarinic effect of Claritin® on tear flow and tear volume. Fluorophotometry is a sensitive tool for measuring miniscule quantities of fluorescein dye in the pre-corneal tear film. With this device tear flow and volume can be monitored objectively to show any alterations that may occur with antihistamine use. Methods:Baseline tear flow and tear volume was determined with a fluorophotometer in six normals. The patients were then dispensed Claritin (loratadine 10 mg) and instructed to dose QD for four days. Following the four days of treatment, tear flow and tear volume were re-evaluated. Results:After four days of dosing with Claritin QD, mean tear flow decreased by 0.790 micro-liters/minute from a baseline value of 1.654 micro-liters/minute to a post treatment value of 0.864 micro-liters/minute. Mean tear volume also decreased post treatment by 3.497 micro-liters from a baseline value of 8.615 micro-liters to a post treatment value of 5.118 micro-liters. Conclusion:The evaluation demonstrated that both tear flow and tear volume decrease in this population after taking Claritin. It also observed that alterations in tear production and volume can be accurately measured with fluorophotometry. Fluorophotometry may be used as a precise way to determine the efficacy of new dry eye therapies that alter tear production.
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