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Drops to Prevent DropoutsHere’s what and how to prescribe for allergy patients who wear contact lenses.Joseph P. Shovlin, O.D. Associate Clinical Editor Michael D. DePaolis, O.D. Sherry WinnMild allergic reactions respond well to the time-honored regimen of cold compresses and artificial tears. But in moderate to severe allergic reactions, the levels of histamine and other mediators are significantly elevated. So when cold compresses and tears no longer do the trick, an ever-expanding line of ocular medications comes to the rescue. Customize your regimen to the severity of the disease and patient’s symptoms. When a condition warrants pharmaceutical treatment, educate the patient about how to use the medications with contact lenses. In most cases, patients should discontinue or reduce contact lens wear while undergoing treatment (see Levels of Lens Wear). If the patient wears contact lenses during treatment, instruct her to wait at least 5 minutes after she instills the drops before inserting her lenses. To ensure your patients comply, the drugs should be easy and convenient to use, safe for prolonged use in both adults and children, provide rapid and prolonged relief, and ideally prevent recurrences.1 Many of the new drugs fulfill these demands. They work by different mechanisms to combat the annoying symptoms of allergic reactions. We can separate the current selection of drugs into six categories: antihistamines, antihistamine/vasoconstrictor combinations, mast cell stabilizers, antihistamine/mast cell stabilizers, NSAIDs and steroids. AntihistaminesIn the allergy process, histamine and cytokines recruit other inflamed cells to dilate surrounding blood vessels and produce swelling. Topical antihistamines compete with the body’s natural histamine for the H1 receptor. They usurp the receptor site, precluding histamine from creating an allergic response.The currently available topical ocular antihistamine drugs include levocabastine (Livostin), emadastine (Emadine) and antazoline/naphazoline (Vasocon-A). These medications are typically prescribed bid to qid for 1-2 weeks, and then bid thereafter as needed for itching. Add oral antihistamines concomitantly to relieve systemic allergic symptoms. Examples include cetirizine (Zyrtec), fexofenadine (Allegra) and loratadine (Claritin). Antihistamine/vasoconstrictorsTopical ocular antihistamine/vasoconstrictor combinations include OcuHist, Opcon-A and Naphcon-A. The antihistamine portion of the drop relieves itching, while the vasoconstrictor relieves the associated redness. Interestingly, the combination of the two is more effective in reducing the signs and symptoms of allergic conjunctivitis than either agent alone.Antihistamine/vasoconstrictor combinations are available OTC and are relatively inexpensive. But these drugs are only effective for a short duration (2-4 hours). They’re not approved for use in children and can be associated with mydriasis and rebound hyperemia, although the latter does not typically occur in the eye. Another precaution is that vasoconstrictors alone or in combination with antihistamines can cause acute and chronic inflammatory conjunctivitis. This can take several weeks to resolve after the patient discontinues the drug. So, many optometrists prefer not to recommend these OTC agents. Also, since these agents produce an alpha-adrenergic vasoconstrictor response, you cannot use them in patients who have cardiovascular problems or in those who are taking MAO inhibitors.1-3 Mast Cell StabilizersThis class of drugs inhibits the degranulation of mast cells, preventing them from releasing histamine and other allergy mediators. When used correctly and over a period of time, these drugs can almost eliminate the occurrence of allergic reactions in susceptible patients.Mast cell stabilizers are relatively safe and efficacious, but require a loading time of a few days and continuous use. These drugs are effective for prophylaxis, but have no effect on acute episodes. They include cromolyn sodium (Crolom, Opticrom) and lodoxomide (Alomide). Alomide both stabilizes mast cells and suppresses the release of eosinophilic major basic protein. It’s safe for children, and patients can use it qid for up to 3 months. Nedocromil sodium (Alocril) and pemirolast potassium (Alamast) are two other drugs recently approved in the U.S. (See New Relief in Sight.) Mast cell stabilizers are the main treatment for giant papillary conjunctivitis patients for whom you’ve already changed their lenses, materials, care system and wearing time. Doctors typically prescribe them bid to qid. Patients can use them while wearing RGPs or disposable soft lenses. Although there’s some debate, many doctors say it’s OK for patients wearing yearly soft lenses to instill two of the four daily drops while wearing their lenses.1,2 Antihistamine/Mast Cell StabilizersThis class is the most recent addition to the arsenal of anti-allergy drugs. Foremost are olopatadine (Patanol) and ketotifen fumarate (Zaditor).Patanol not only offers long-lasting action and bid dosage, but is safe for children over 3. It is a relatively selective H1-receptor antagonist that relieves itching in two ways. Immediately upon instillation, Patanol binds to the H1 receptors, preventing histamines from binding to them and providing quick relief from itching. As the drug further penetrates, it prevents cross-linking between IgE receptors, preventing mast cell degranulation and histamine release.1 An added benefit of Patanol for RGP or 2-week disposable users is that they can instill the second drop while wearing the lenses.2 (They should instill the first drop before lens insertion.) The newest drug in this class is ketotifen fumarate (Zaditor), CIBA Vision’s response to Patanol. Like its counterpart, Zaditor is also long-acting and can be administered bid. Zaditor functions somewhat differently from Patanol. In the allergic process, histamine is a preformed mediator. It’s stored in the cytoplasmic granules of mast cells and basophils, and is released by exocytosis. Zaditor works by inhibiting the influx of calcium ions into the mast cell, thus preventing both histamine and leukotriene release.4 It also inhibits release of mediators from neutrophils and basophils.5 Research has shown that substances such as 48/80 and substance P (SP) release histamine from mast cells in a calcium-free medium. Ketotifen inhibits this release.6 NSAIDsNon-steroidal anti-inflammatory drugs are another line of defense against allergies. NSAIDs such as ketorolac tromethamine (Acular) and diclofenac sodium (Voltaren) raise the sensory threshold of peripheral nerve endings high enough to sometimes abate the itch sensation. NSAIDs act by blocking the cyclooxygenase pathway and subsequent formation of inflammatory mediators.An NSAID is the drug of choice when the predominant finding is conjunctival inflammation. Doctors generally prescribe NSAIDs qid for 1-2 weeks, and then bid or tid as needed for itching. Use NSAIDs with caution: They sting upon instillation, are not adequate to handle severe cases of atopic disease, and can cause epithelial toxicity with prolonged use.2,3 SteroidsAlthough side effects of steroids are numerous, they do greatly help relieve allergic symptoms. Steroids prevent the hydrolysis of arachidonic acid, thus blocking leukocytic migration. This stabilizes lysosomal membranes, inhibits neovascularization, inhibits histamine synthesis, and decreases capillary permeability.Loteprednol etabonate 0.2% (Alrex)—a weaker version of the steroid Lotemax (loteprednol etabonate 0.5%)—is proving effective as the first topical steroid approved by the FDA for treating ocular allergy. Alrex is “site-specific,” meaning that the active drug resides at the target tissue only long enough to render a therapeutic effect. It reduces the potential for side effects such as increased IOP, posterior subcapsular cataracts, delayed wound healing, enhanced susceptibility to infection and rebound anterior uveitis. Alrex suppresses any inflammatory conjunctivitis that may accompany itching. You can also use more potent steroids such as rimexolone (Vexol), fluorometholone acetate (Flarex), prednisolone acetate (Pred Forte) and Lotemax to relieve hyperacute allergic situations. In these instances, have the patient use the drops every 3 hours for the first 2 days to quiet the response. Once the severity of symptoms diminishes, substitute other anti-allergy medications or use them concomitantly at a reduced dosage.2,3 Future TherapiesResearchers are continually advancing toward newer and better treatments to combat ocular allergies. In the future, cyclosporine A 0.05% solution (Restasis) may offer a more efficacious and slightly less toxic alternative to allergy treatment, especially when the cornea is involved.Systemic immunization is gaining acceptance for patients who suffer from systemic symptoms. Through this technique, a new set of blocking antibodies is being established.3 Although many allergic conditions are seasonal, there are many that can affect a patient any time of the year. A good clinician should understand the many conditions associated with allergic responses in the eye and the treatments available for the contact lens wearer. If you take a careful history, perform a scrutinizing clinical examination
and provide appropriate use of available drugs, then most of your patients—including
allergy sufferers—can enjoy safe contact lens wear. For allergy patients
who can’t tolerate contact lenses, spectacles and refractive surgery remain
viable options.
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Levels of Lens WearWhen treating allergic conjunctivitis in a contact lens patient, establish the severity of the condition and determine what effect, if any, treatment it’s going to have on contact lens use.
When the contact lens may be the inciting factor, consider several options: reduce wearing time; refit the patient in daily soft lenses or rigid gas permeable lenses; or in more severe cases, discontinue lens wear completely. |
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How to Win this Allergy Season
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