A comparison of the efficacy and tolerability of olopatadine hydrochloride 0.1% ophthalmic solution and cromolyn sodium 2% ophthalmic solution in seasonal allergic conjunctivitis

Abstract

Background: Treatments for allergic conjunctivitis have various mechanisms of action. Cromolyn sodium stabilizes conjunctival mast cells by preventing calcium influx across the cell membrane, whereas olopatadine hydrochloride is both an antihistamine and a mast cell stabilizer. Objective: This study compared the efficacy and tolerability of olopatadine and cromolyn in controlling the ocular signs and symptoms of seasonal allergic conjunctivitis. Methods: This was a multicenter, randomized, double-masked, parallel-group trial. One group instilled olopatadine 0.1% ophthalmic solution and placebo BID, and the other instilled cromolyn 2% ophthalmic solution QID, both for 6 weeks. The formulation of cromolyn used in this study is currently available only in Europe and Australia. Results: The intent-to-treat efficacy and safety analyses included 185 patients, 91 in the olopatadine group and 94 in the cromolyn group. At 30 minutes after the first instillation, respective decreases of ∼30% and ∼20% were reported in self-rated ocular itching and redness with both treatments; by 4 hours, itching had decreased by ∼38% in both groups. Differences between treatments were not statistically significant. At 4 hours, redness had decreased by ∼38% and ∼26% in the respective treatment groups. By day 42, both treatments had produced significant reductions from baseline in ocular signs and symptoms; however, the reductions in itching and redness were significantly greater with olopatadine compared with cromolyn (both variables, P < 0.05). The difference in physicians' impression of overall improvement on days 30 and 42 significantly favored olopatadine over cromolyn (both days, P < 0.05). Most patients (62.2%) had reacted positively to grass pollen at baseline. The regression slopes correlating itching and redness with pollen count were 5 times lower for olopatadine compared with cromolyn ( P = 0.002 and P = 0.016, respectively), indicating that olopatadine's efficacy increased as the pollen count increased. Conclusions: Six weeks' instillation of olopatadine 0.1% ophthalmic solution BID had a significantly greater effect on the ocular signs and symptoms of allergic conjunctivitis compared with 6 weeks' instillation of cromolyn 2% ophthalmic solution QID. Both treatments were well tolerated by patients in all age groups; however, olopatadine appeared to have better local tolerability in children aged <11 years.