Mast cell stabilizer helps with long-term ocular allergies

Carlsbad, CA-The mast cell stabilizer pemirolast potassium ophthalmic solution 0.1% (Alamast, Santen Inc.) can be an effective immediate and long-term treatment for ocular surface allergies because of its inhibitory properties as well as its safety profile, suggested Bill G. Bell, MD, an ophthalmologist in private practice in Carlsbad, CA.

"Pemirolast potassium ophthalmic solution is best used in a situation where you know you need a very safe, long-term profile medication, you need a medication that does not cause drying, and you need a medication that stabilizes the actual allergic process. And you need a medication with which you can be comfortable knowing, in any age group, that the safety profile is one where the patient can keep using the medication for weeks or months if necessary," Dr. Bell said.

Pemirolast inhibits the antigen-induced release of inflammatory mediators such as histamine and leukotriene C₁, D₄, E₄ from human mast cells. It also interferes with the chain of events through which sensitized mast cells release pre-formed mediators and later-formed mediators when re-exposed to the sensitizing agent.

Prescribing pemirolast or any other medication for ocular surface allergies is one of the later steps in a process that begins with identifying and removing as many offending allergens as reasonable from the patient's environment, Dr. Bell said.

When the time comes to review the options for medical therapy, he considers a variety of factors, including the patient's symptoms, findings from the examination, and the frequent confluence of ocular surface allergy and lubrication problems.

Minimal drying For many patients with ocular surface allergies, the preferred medication is a product with no antihistamine or an antihistamine that causes very minimal drying. "When I'm treating a person and picking a medication such as pemirolast, I'm probably going to pick that for a person that I'm pretty sure has a significant ocular lubrication problem, because without an antihistamine the medication is not going to make their lubrication problem worse," Dr. Bell said.

He also prefers nonsteroidal agents, because even the newest drugs in this category may increase the risk of elevation of IOP, compromise the immune system on the ocular surface, or cause internal changes such as cataract development.

"How does pemirolast fit into this profile? One reason why it is one of my favorite medications is that it does have, in its own carrier substance, a very good lubrication agent," Dr. Bell said.

"And although it has no antihistamine, most people will tell you that it gives them an immediate effect, maybe not as profound as an antihistamine, but within the first day in most people.

"What I tell my patients is that you are getting a very good lubricating agent. As you use it, not only are you lubricating and soothing the surface, you are also stabilizing the troublemaker (mast cells), so the problem is going to become less and less," Dr. Bell said.

Pemirolast also meets his other important criterion of long-term safety. "Pemirolast, to my knowledge, has had virtually no sight-threatening, long-term problems reported. It certainly doesn't come up in the literature, and most of the problems that we see are the same ones encountered with other ocular surface allergy products, which are often difficult to separate from the symptoms of ocular allergies themselves," he said.

While Dr. Bell often prescribes pemirolast, he is careful to note that every case is different.

"Go down your checklist and pick what you think is most effective, but always remember that patients with allergy are unique individuals. They do not necessarily react to the same things that their relatives do, and also you may very well have a family where two family members have a wonderful reaction to pemirolast and a third family member does not," he said.

"You have to keep your mind open. You make your best first-line choice. When you re-evaluate, you decide do I continue this medication, do I add to this medication, or do I change it completely?" he added.