Allergy drug has multiple mechanisms of action

New York-As one of the category of ocular allergy drugs that target several substances in the allergic cascade, ketotifen fumarate ophthalmic solution, 0.025% (Zaditor, Novartis Ophthalmics) is effective at treating immediate symptoms and controlling chronic reactions, according to Penny A. Asbell, MD, FACS, MBA.

"What's really new in ocular allergy is that we do have drugs with multiple mechanisms of action," said Dr. Asbell, who is professor of ophthalmology and director, cornea and refractive surgery, Mount Sinai School of Medicine, New York. "In the past we had drugs that were vasoconstrictors that got rid of some of the redness related to eye irritation and eye allergy. We also had drugs that were specific antihistamines, and histamine is a big part of any allergy, including eye allergies. Now we have drugs that work in several different modalities, and one of the drugs that works that way is ketotifen."

Together, ketotifen's combined mechanisms of action make it an effective inhibitor of the type I hypersensitivity response to allergen, she said.

"It does a couple of different things. Mast cells are considered one of the key instigators of the inflammatory process in allergies. They release histamine, they make more histamine, and they make other cytokines as well," she said. "Ketotifen and a group of drugs like it stabilize cell membranes so that they don't make more or release more. They also inactivate histamine that may have already been released."

Ketotifen also works on eosinophils, which are considered an important part of the more chronic or persistent allergic reaction rather than just the immediate reaction, Dr. Asbell said.

"There's good evidence that ketotifen will prevent eosinophils from coming into the picture and causing that chronic response. The big difference in ketotifen versus the other products is primarily that it blocks eosinophils' contribution to the allergic response. That's a labeling indication that the other products don't have. This may be particularly important for the patients who have more chronic allergic responses," she continued.

Dosing a plus

However, there are similarities between ketotifen and the other drugs in this category that also have multiple mechanisms of action, Dr. Asbell said.

"One of the things that people should be thinking about is trying one drug, and if the patient does not get an adequate response, it's not unreasonable to try one of the other agents in that group," she noted.

"I try one, and I tell patients that there are other products besides this one," Dr. Asbell said, explaining that she doesn't want patients to become discouraged and think that there is no agent that will relieve their allergic symptoms or prevent new occurrences.