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How Do You Spell Relief? What's the best way to help your allergy patients cope with their problem? This month, the experts weigh in with advice.

What you can use to relieve your patients' allergic eyes.

ALLERGY UPDATE

Treating patients who come to you with itchy, watery eyes can be challenging. A long list of potential medications and coexisting medical conditions can cloud the diagnostic picture. Let's review some of the finer points of diagnosing seasonal allergies and get updated on the latest in medical treatment.

Is it allergy?

You first need to rule out other reasons for these patients' red, irritated eyes. Look for:

> dry eyes

> blepharitis

> bacterial conjunctivitis

> hypersensitivity reactions to medications.

Because the signs of allergy that you observe at the slit lamp can be minimal, it's especially important to take a thorough history. One of the key complaints in allergic conjunctivitis is itching, which may be accompanied by redness, chemosis, tearing and lid swelling. One basic guideline often holds true: "If it itches it's allergy, if it burns it's dry eye and if it's sticky it's bacterial."

Patients who just have dry eye don't have itching. Patients who have seasonal allergies rarely demonstrate the discharge associated with bacterial conjunctivitis. Patients who just have blepharitis have some intermittent itching, but it isn't the predominant symptom.

When ruling out hypersensitivity reactions, remember that many eye drops, including some glaucoma medications, contain a benzalkonium chloride preservative that can cause toxicity reactions. In addition, contact lens wearers may have allergic reactions to the solutions or to the lenses themselves. To eliminate these possible culprits, have the patient temporarily discontinue contact lens use and see if the symptoms resolve.

Treating allergy

There are 14 types of eye drops that fall into five pharmacological classes of drugs for ocular allergy. This broad range of options should allow you to treat individual patients according to their specific ailments and lifestyles. As a review, the five classes and 14 drops are:

1 Topical antihistamines. These agents combat redness and swelling as well as itch. They have little impact on other proinflammatory mediators, such as prostaglandins and leukotrienes but provide short-term, rapid symptomatic relief of itch. Topical antihistamines include:

> emedastine difumarate (Emadine)

> levocabastine HCI (Livostin)

2 Topical mast cell stabilizers. These medications orevent mast cell degranulation. They don't relieve existing symptoms of allergy; they prevent them from occurring. The patient must take them regularly and prophylactically before actually having a problem. Topical mast cell stabilizers include:

> pemirolast potassium (Alamast)

> cromolyn sodium (Crolom)

> lodoxamide tromethamine (Alomide)

> nedocromil sodium (Alocril)

3 Topical antihistamines/mast cell stabilizers. These dualacting compounds are excellent for treating ocular allergy because they combine the fast response of antihistamines with the prolonged action of mast cell stabilizing activity. Topical antihistamines/mast cell stabilizers are:

> olopatadine HCl (Patanol)

> ketotifen fumarate (Zaditor)

> azelastine HCI (Optivar)

4 Topical NSAIDs. Nonsteroidal anti-inflammatory drugs (NSAIDs) inhibit the cyclooxygenase pathway causing a decrease in the production of prostaglandins and thromboxane. Consequently, the itchiness of allergic conjunctivitis decreases. NSAIDs can delay corneal wound healing and patients must take them q.i.d. Topical NSAIDs include:

> ketorolac tromethamine (Acular)

5 Topical corticosteroids. Because of potential side effects, you should only prescribe topical steroids when severe allergic conjunctivitis doesn't respond to other treatment modalities. Try a mild steroid with a good safety and efficacy profile, such as loteprednol, or prescribe a stronger steroid to initially decrease symptoms and then switch over to a combination mast cell stabilizer/antihistamine. Topical corticosteroids include:

> loteprednol etabonate (Alrex)

> rimexolone (Vexol)

> fluorometholone (FML)

> prednisolone acetate (Pred Forte)

The new kids on the block

Mast cell degranulation on the conjunctiva causes the clinical symptoms of allergy. A cascade of events results, leading to increased levels of histamine on the ocular surface. Drugs known as mast cell stabilizers reduce the amount of degranulation and histamine that the mast cells release. Antihistamines act against histamine, which has already been released.

For symptomatic relief of acute, mild hay fever conjunctivitis, an antihistamine may prove effective. But patients who have chronic ocular surface allergy need to stabilize their mast cells long term.

Four medications, introduced in the past 2 years, can help combat the symptoms of allergic conjunctivitis. They are:

* Pemirolast. This mast cell stabilizer treats allergy by inhibiting the antigen-induced release of inflammatory mediators from human mast cells. It also prevents the chemotaxis of eosinophils into ocular tissue. Although it's fairly effective against itch, it can take several weeks to take effect. Pemirolast is best for seasonal allergy sufferers who can take the drug prophylactically. It's currently recommended for q.i.d. dosing.

* Nedocromil. This mast cell stabilizer works relatively well at relieving itching caused by allergic conjunctivitis. Its b.i.d. dosing is adequate for patient compliance. Like pemirolast, it can take a couple of weeks for the patient to attain relief.

Be aware that this drug seems to have a high number of adverse reactions. For example, 40% of patients taking this drug experience headaches, and another 10% to 30% complain of ocular burning and stinging, unpleasant taste and nasal congestion. These adverse reactions can cause a patient to discontinue therapy.

* Azelastine. This H1 antagonist inhibits the release of histamine and other cell mediators involved in the allergic response. There's some evidence that it also helps stabilize mast cells. The dosing for azelastine is b.i.d.

* Ketotifen. This is an excellent combination mast cell stabilizer and antihistamine. Unlike some other drugs in its class, it offers true b.i.d. dosing - one drop lasts 12 hours instead of 8. This long duration of action is especially nice for contact lens wearers. There's a slightly higher rate of burning/stinging upon instillation, however.

Over-the-counter drum

A few over-the-counter (OTC) medications manage seasonal allergic conjunctivitis. Most are simple antihistamines combined with vasoconstrictors, such as naphazoline (e.g., Naphcon, VasoClear, Allerest, etc.). However, they don't adequately manage the condition and can cause rebound redness, leaving the eyes chronically red.

Oral medications

The alternative is oral medications. Some of the more popular drugs include diphenhydramine HCI (Benadryl), fexofenadine HC1 (Allegra), loratadine (Claritin) and cetirizine HCI (Zyrtec). However, many of them have poor ocular penetration. I use them more to control systemic conditions when I think eye drops alone won't properly manage a patient's ocular symptoms.

The best is yet to come

The future will undoubtedly bring new and potent anti-allergic medications with a broad spectrum of therapeutic characteristics. Current research focuses on therapeutic agents such as binding proteins, which are naturally secreted by some insects to combat the host's immune system. We also use immunoglobulin (IgE) blockers as anti-allergy medications.

As primary eyecare providers, we owe it to ourselves and to our patients who suffer from allergies to keep up with these new advances in treatment.

References available upon request.

BY DEEPAK GUPTA, O.D.,

F.A.A.O.

Stamford, Conn.

Dr. Gupta has no financial interests in any of the companies or products mentioned in the article Reach him at deegup4919@hotmail.com.

Copyright Boucher Communications, Inc. Mar 2002
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