Epinastine provides rapid-onset allergy relief, study shows

In patients with a history of conjunctivitis, symptoms resolved within 5 minutes of topical application, and relief lasted up to 12 hours.

Issue: August 1, 2004

ByNicole Nader

Topical epinastine relieved ocular allergy symptoms within 5 minutes of application, according to a poster presented by Mitchell H. Friedlaender, MD, and colleagues at the meeting of the Association for Research in Vision and Ophthalmology.

“Due to its unique mechanism of action, epinastine not only reduced symptoms of discomfort, but also appearance-related [allergy] symptoms, which often impact patients’ daily activities and self esteem,” Dr. Friedlaender, of the Scripps Clinic, said in a press release.

Marketed as Elestat (0.5% epinastine HCl) by Allergan Inc. and Inspire Pharmaceuticals Inc., epinastine is a topical ophthalmic antihistamine that works to stabilize mast cells, preventing inflammation and reducing ocular itching and erythema associated with conjunctivitis.

“Epinastine’s mechanism of action features a greater affinity for H2 receptors than other antihistamine/mast cell stabilizers and since H2 receptors are more commonly found on blood vessels than H1 receptors, epinastine could potentially be more effective in the relief of swelling than other dual-action agents,” officials said in a press release.

Change in facial edema from pre-challenge shown by radial difference map. Arrows show regions of swelling 20 minutes after allergen challenge compared to a pre-challenge scan. There is edema in the vehicle-treated eye and a lack of edema in the epinastine-treated eye.

Image courtesy of Mitchell H. Friedlaender, MD.

Dr. Friedlaender’s presentation noted that the drug’s anti-inflammatory actions can inhibit IL-8 release from eosinophils, chemotaxis, expression of adhesion molecules and oxygen radical generation from neutrophils and eosinophils.

Allergen challenge

The antihistamine qualities of epinastine were tested in an allergen-challenge study. Researchers at the Scripps Clinic recruited 30 female patients between the ages of 18 and 75. Patients had a history of allergic conjunctivitis and were sensitive to allergens found in airborne pollen, cigarette smoke, mold, pet hair, insects and chemicals found in food, clothing and fragrances.

At the time of the study, patients discontinued their use of systemic antihistamines, corticosteroids, ocular medications and contact lens wear. Patients who had ophthalmic abnormalities, were pregnant or lactating or underwent ocular surgery in the 6 months preceding were excluded from the study.

Before the allergen challenge, patients were tested for their allergy threshold. “On day 0, the amount of antigen that elicited itching and hyperemia scores of 2 or greater (on a 0 to 4 scale) was established as the threshold dose,” the authors said in the study abstract.

Seven days after this test, patients were randomized to receive one drop of 0.5% epinastine in one eye and one drop of vehicle in the fellow eye. Five minutes later, a conjunctival allergen challenge (CAC) test was given. Fourteen days later, patients received a second dose of 0.5% epinastine in one eye and vehicle in the fellow eye and subsequently received the CAC 12 hours later.

Patients rated their response for itching on a scale of 0 to 4 in a questionnaire that was taken 5, 10 and 15 minutes before each CAC. Researchers examined patients for signs of edema or erythema.

Rapid resolution

Patient evaluation and physician examination showed that epinastine provided allergy relief when applied 5 minutes before the CAC.

“[It] provided significant relief of itching when compared to vehicle (mean itching score of 1.14 at 5 minutes post-challenge, compared with 2.07 for eyes treated with vehicle),” the study authors said. This difference was statistically significant (P = .008).

Additionally, erythema was prevented or reduced when epinastine was applied before CAC. “The onset mean hyperemia scores at 5 minutes post-challenge were 0.86 for epinastine-treated eyes and 1.93 for vehicle-treated eyes,” study authors said. This difference was also statistically significant (P = .026).

The therapeutic effects of epinastine were found to last for up to 12 hours. Eyes that were treated with epinastine in the 12 hours before the CAC had an average itching score of 1 (on a 0 to 4 scale), according to patient questionnaires. Eyes that were not treated with epinastine and received vehicle treatments had an average itching score of 2.25. The difference was significant (P = .011).

For Your Information:

Mitchell H. Friedlaender, MD, is the head of the division of ophthalmology at Scripps Clinic, director of the Scripps Clinic Laser Vision Center and adjunct professor at The Scripps Research Institute. He can be reached at Scripps Clinic, 10666 North Torrey Pines Road, La Jolla, CA 92037; 858-554-9103; fax: 858-554-6150; e-mail: mfried@scrippsclinic.com. Dr. Friedlaender has no direct financial interest in the products mentioned in this article, nor is he a paid consultant for any companies mentioned.

Allergan can be reached at 2525 Dupont Drive, Irvine, CA 92612; 800-433-8871; fax: 714-246-5913; Web site: www.allergan.com. Inspire Pharmaceuticals can be reached at 4222 Emperor Blvd., Suite 470, Durham, NC 27703-8466; 919-941-9777; fax: 919-941-9797; Web site: www.inspirepharm.com.