Higher-concentration olopatadine yields superior activity

Maui, HI-Results of a double-masked, randomized, placebo-controlled study demonstrated olopatadine 0.2% (Pataday, Alcon Laboratories) was more effective for preventing allergen-induced ocular itching and redness than epinastine 0.05% (Elestat, Inspire Pharmaceuticals and Allergan). In addition, the new higher-concentration formulation of olopatadine was more comfortable than epinastine, reported Francis S. Mah, MD, here at the annual meeting of the Western Society of Allergy, Asthma & Immunology.

Dr. Mah was one of the investigators in the 7-week single-center study that used the conjunctival allergen challenge (CAC) model to compare the efficacy and comfort of the two anti-allergy products. He is assistant professor of ophthalmology and co-medical director, Charles T. Campbell Eye Microbiology Laboratory, University of Pittsburgh School of Medicine, Pittsburgh.

The study enrolled 92 patients who demonstrated a positive response to allergen challenge during screening and were pretreated with their assigned study medication 5 minutes or 12 hours before allergen challenge in onset of action and duration of action testing, respectively.

"Olopatadine 0.2% extends all of the benefits of olopatadine 0.1% as a safe and effective anti-allergy agent but with a longer duration of action that allows the added convenience of a once-a-day drop," Dr. Mah said.

"The results of this CAC study confirm a previous investigation comparing olopatadine 0.2% and epinastine 0.05% and are not at all surprising considering that the original formulation of olopatadine containing 0.1% of the active ingredient has also been shown to be superior to epinastine 0.05% for relieving ocular itching and redness," he added.

Formulation changes

In addition to containing double the concentration of olopatadine, the new once-a-day product features some formulation changes, including the addition of povidone as a solubilizer.

"Povidone is an ingredient that is used in various artificial tear formulations and in addition to increasing the solubility of the higher concentration of olopatadine, it enhances product comfort," Dr. Mah said.

In the CAC study he reported, participants were randomly assigned 3:3:3:1 into the four treatment groups: olopatadine 0.2% in one eye/placebo contralaterally; epinastine 0.05% in one eye/placebo contralaterally; olopatadine 0.2% in one eye/epinastine 0.05% contralaterally; and placebo bilaterally.

"Both of these products are very good anti-allergy products," Dr. Mah said. "This design was intended to give the study sufficient power to detect statistically significant differences."

Itching was assessed at 3, 5, and 7 minutes postallergen challenge and redness was assessed after 7, 15, and 20 minutes. In the onset-of-action investigation, olopatadine 0.2% was associated with significantly lower mean ocular itching scores compared with epinastine 0.5% at 5 and 7 minutes, and there was a trend favoring olopatadine at the first assessment at 3 minutes. Olopatadine 0.2% was significantly superior to epinastine 0.5% for preventing ocular itching at all time points in the duration-of-action investigation.

Redness was rated in the ciliary, conjunctival, and episcleral beds. The mean redness scores were significantly lower after olopatadine 0.2% treatment compared with epinastine 0.5% for all anatomic locations at all time points (in both onset and duration of action testing).

Better mast cell stabilizing activity might account for the benefits of olopatadine 0.2% in this study, Dr. Mah proposed.