The objective of this study was to evaluate the efficacy of 0.05%
levocabastine, a new
antihistamine formulated for ophthalmic use, compared with the placebo vehicle for the treatment of
allergic conjunctivitis induced by ocular
allergen challenge. Subjects who reacted. positively in both eyes on two separate occasions to ocular
allergen challenge with grass, ragweed, or cat dander (N = 47) received one dose of 1 to 2 drops of 0.05%
levocabastine in one eye and its vehicle in the other eye. After 10 minutes, the predetermined dose of
allergen was instilled in both eyes. Signs and symptoms of
allergic conjunctivitis were evaluated with biomicroscopy and subjective evaluation of
itching after 3, 5, and 10 minutes. Four hours after
drug administration, subjects were rechallenged and reevaluated to determine
levocabastine's duration of action. Results showed that
levocabastine was significantly more effective than placebo in inhibiting
itching,
hyperemia, eyelid swelling, chemosis, and tearing after the initial challenge and in inhibiting all parameters except eyelid swelling after the rechallenge 4 hours later (p < 0.05). These results demonstrate that
levocabastine, currently the only ophthalmic
antihistamine available that is not combined with a
vasoconstrictor, is efficacious in the inhibition of
itching, as well as all of the allergic signs of a vascular origin, with a duration of action of at least 4 hours. Because of its strong effects on
itching and
hyperemia, chemosis, lid swelling, and tearing,
levocabastine would be a valuable therapeutic agent to add to the heterogeneous family of
antiallergic compounds presently available for the treatment of seasonal
allergic conjunctivitis.