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G Gupta, GW Ousler, SD Pollard, MB Abelson; The Comparative Ocular Drying Effects between Claritin® and Zyrtec® in Normal Adults . Invest. Ophthalmol. Vis. Sci. 2002;43(13):70.
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Purpose: It has been suggested that the antimuscarinic action of oral antihistamines may diminish the aqueous phase of the tear film, leading to exacerbated signs and symptoms of dry eye. This study investigates a possible ocular drying effect associated with the antihistamines Claritin® (loratadine) and Zyrtec® (cetirizine) in a controlled adverse environment (CAE). Methods: Eighteen (18) normals were evaluated in a CAE regulating humidity (< 4%), temperature (76°F), airflow (non-turbulent), and visual tasking (television monitor). Clinical assessments included blink rate, tear film break-up time (TFBUT), corneal staining, tear volume, tear flow, and patient reported ocular discomfort. Following baseline (Day 0) examinations, patients were exposed to a CAE for 45 minutes. Ocular discomfort was measured during exposure at fixed time points. Blink rate, TFBUT, and corneal staining were re-measured after exposure. Nine (9) patients were then dispensed loratadine (10mg) and instructed to dose QD for 4 days while the remaining 9 were dispensed cetirizine (10mg) and instructed to dose QD for 4 days. After treatment, patients were re-exposed to a CAE (Day 4) and given similar examinations as at Day 0. Results: After 4 days, QD dosing of loratadine yielded a mean increase, on a 0-4 scale, of 0.75 (107%) in keratitis (p<0.001), a mean increase of 1.35 (133%) in conjunctival staining (p<0.001), a mean decrease of 1.38 seconds (33.7%) in TFBUT (p<0.001), and a mean increase, on a 0-4 scale, of 0.32 (24.8%) in ocular discomfort scores (p=0.050). QD cetirizine dosing yielded a mean increase of 0.57 (60%) in keratitis (p<0.001), a mean increase of 0.7 (49.7%) in conjunctival staining (p=0.005), a mean decrease of 0.76 seconds (19.6%) in TFBUT (p=0.050), and a decreasing trend in ocular discomfort scores of 0.11 (10%). Increased conjunctival staining was induced by CAE exposure in normals to a significantly greater extent (93%, p=0.04) with loratadine than cetirizine. Conclusions: It was observed that both signs and symptoms associated with ocular dryness, including increased corneal and conjunctival staining, decreased TFBUT, and increased ocular discomfort, were induced by CAE exposure in normals after taking loratadine or cetirizine. Furthermore, loratadine significantly increased conjunctival staining when compared to cetirizine. The data suggests that loratadine may cause more clinically significant damage to the ocular surface than cetirizine.
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