Allergic Conjunctivitis: Pharmacists on the Front Line

Pharmacists are often the first health care providers to make contact with patients needing medical advice for ocular disorders such as allergic conjunctivitis (AC), especially in the spring and summer months. A review of AC and counseling points are presented here.

Case Study It is springtime, and a young regular client of the pharmacy comes in and asks the pharmacist for eye medicine to relieve acute, severe eye itching and irritation, tearing, redness, and watery discharge. Is this allergic conjunctivitis or a bacterial or viral eye infection? What can the pharmacist recommend for this patient?

B

oth younger and older people with acute ocular conditions may ask a pharmacist about purchasing a nonprescription medicine to relieve painful signs and symptoms of ocular discomfort. Often pharmacists are the first health care providers to make contact with patients needing medical advice for ocular disorders such as allergic conjunctivitis (AC). This overview of AC and major eye structures will prepare pharmacists to better counsel patients with the condition.

Anatomy of the Eye

The visible external portion of the eye is composed of the cornea and sclera. The cornea is enervated, whereas the sclera is not. The sclera is a white, tough, caliginous layer that gives the eye rigidity and encases internal eye structures. The conjunctiva is a thin, clear mucous membrane consisting of cells that covers the sclera and lines the inside of the eyelids. It consists of the nonkeratinizing squamous epithelium. One of the conjunctiva’s primary functions is to help lubricate the eye by producing mucus and tears, although the volume of tears it produces is less than that of the lacrimal gland. It also contributes to immune surveillance and helps to prevent the entrance of microbes into the eye.

Allergic Conjunctivitis Defined

AC is one of the most common seasonal ocular allergies. This condition involves inflammation of the conjunctiva, usually due to an allergy.¹ Most individuals develop AC when their eye is exposed to an allergen—a substance that makes the body’s immune system overreact. As a result, the eye can become sore and inflamed.

The ocular allergic response results from a cascade of events mediated by mast cells.^2,3 Beta chemokines (ie, eotaxin and macro-phage inflammatory protein 1 alpha) have been implicated in the priming and activation of mast cells on the ocular surface. When an allergen is present, sensitization takes place and launches an antigen-specific response. Th2-differentiated T-cells release cytokines, which promote the production of antigen-specific immunoglobulin E (IgE). IgE binds to IgE receptors on mast cell surfaces. This process initiates the release of histamine, which leads to release of cytokines, prostaglandins, and platelet activation factor. Mast cell intermediaries cause allergic inflammation and symptoms through the activation of inflammatory cells. As histamine is released, it binds to H₁ receptors on nerve endings and causes ocular itching. Histamine also binds to H₂ receptors of the conjunctival vasculature and causes vasodilation. Mast cell—derived cytokines recruit neutrophils and eosinophils, which promote increased sensitivity.

Common Causes

Pollen is the most common allergen to cause conjunctivitis. It is referred to as seasonal allergic conjunctivitis (allergic rhinoconjunctivitis), because it occurs most often in the spring and summer months when plants, especially grass, trees, and flowers, are in pollen. Some individuals may have symptoms in early autumn or fall. In a normal season, a pollen count of 120 is considered high. During peak times, the pollen count may rise to 6000 or more. Common allergens include:

• Pollen (eg, trees, grass, ragweed)

• Animal fur, skin, or saliva

• Cosmetics, make-up, perfumes

• Dust mites

• Air pollution

• Smoke

• Skin/topical medicines

Symptoms

When an allergen contacts and irritates the conjunctiva, AC symptoms often occur quickly.^4,5 Many individuals with AC have problems with both eyes. At least 20% of the nation’s population is affected by pollen, and about 5% have a strong enough reaction that they need see an allergy specialist. Some individuals will have only mild symptoms, while others state that it is like having a bad cold for 2 to 3 months. Symptoms occur because the overreacting immune system makes the body release histamine and other active substances from mast cells. These substances cause dilation of blood vessels, which irritates the nerve endings and causes increased tearing. The following symptoms are the most typical for AC:

• Red/pink, watery eyes—this is one of the most common symptoms. The eyes become irritated as the small capillaries in the conjunctiva membrane dilate.

• Pain—some individuals may have pain in one or both eyes. Individuals with painful, red eyes, photophobia (sensitivity to bright light), and impaired vision should see a physician immediately.

• Itching—about 75% of individuals experience itching. Rubbing them may worsen the problem.

• Swollen eyelids—as the conjunctiva become inflamed or if the individual has been rubbing them consistently, the eyelids may puff up.

• Soreness—as the conjunctiva become more inflamed, soreness/tenderness or burning may occur.

Prevention Tips for the Patient

The patient should try to identify and avoid the allergens that seem to cause symptoms. If the patient is allergic to pollen or mold, he or she should try to stay indoors when pollen and mold levels are high outdoors when possible. Several sources—including television and radio weather reports, as well as newspapers and Web sites (eg, www. pollen.com)—will include daily allergen count reports. As much as possible, the patient should keep doors and windows closed and use an air conditioner during the spring and summer months. Air filters on the furnace or air conditioner should be changed often. When possible, filters that trap pollen or have a high pollen-filtering code should be used.

Treatment

The goals in treating allergic conjunctivitis include⁵: (1) avoid or remove the allergens, (2) reduce the severity of allergic reaction, (3) provide symptomatic relief, and (4) protect the ocular surface. A number of different types of eye medicines are available to treat AC. In general, they help relieve itchy, watery eyes and may keep symptoms from returning, but do not cure the allergy. Eye drops are often used and may contain an antihistamine, a nonsteroidal anti-inflammatory drug (NSAID) called a mast cell stabilizer, or a combination of these ingredients. Individuals will often begin taking an oral antihistamine product and a mast cell stabilizer eye drop. Corticosteroid eye drops are rarely needed unless symptoms are especially severe or are left untreated for a long period of time.

Antihistamines taken orally work quickly by blocking the effects of histamines produced when the immune system reacts to an allergen. The most commonly used oral antihistamines include cetirizine (Zyrtec), fexofenadine (Allegra), and loratadine (Claritin). These products are classified as low-sedating antihistamines and are dosed once or twice daily. Diphenhydramine (Benadryl) may also be used, but often causes significantly more drowsiness, dry mouth, and dry eyes. Diphenhydramine is dosed 3 or 4 times daily, every 4 to 6 hours. Adverse drug effects of antihistamines most commonly include headache, somnolence, vomiting, and dry mouth. Dosage reduction is suggested in patients with renal impairment and in the elderly.

Mast cell stabilizers take much longer than antihistamines to begin therapeutic effects, but their effects last much longer. A mast cell stabilizer is a class of NSAIDs that reduces the release of inflammation-causing chemicals from mast cells. They block a calcium channel essential for mast cell degranulation, stabilizing the cell, thus preventing the release of histamine. The most commonly used mast cell stabilizer eye drops include ketotifen (Zaditor), lodoxamine (Alomide), and neodocromil (Alocril). These drugs are dosed twice daily, every 10 to 12 hours, except for lodoxamine, which is dosed 3 to 4 times daily. Adverse effects of mast cell stabilizers include burning or stinging, dry eyes, eye pain, tearing, itching, and photophobia.

Many medicated eye drops cause minor burning/stinging when first applied, but this discomfort usually resolves in a few minutes. Contact lenses should not be worn while a patient has AC and is receiving treatment. The use of decongestant eye drops is not recommended. These products only constrict blood vessels in the conjunctiva and do not treat the allergy.

Case Study Resolution

This individual appears to have classic AC. The first-line treatment of AC is to instill nonmedicated artificial tears as needed and start the patient on an oral antihistamine, cetirizine 10 mg once daily. If symptoms persist, the patient may add an ophthalmic mast cell stabilizer product, such as ketotifen or ketotifen fumarate eye drops, twice daily. These products do not require a prescription, are safe to use in individuals 3 years of age and older, and are very effective in relieving the signs and symptoms of AC. If symptoms are not resolved, an oral antihistamine may be added. â– 

Mr. Brown is a clinical pharmacist at Clarian Arnett Hospital and professor emeritus of clinical pharmacy at the Purdue University School of Pharmacy in West Lafayette, Indiana.

References

1. Friedlaender, BL. MH. Allergic conjunctivitis. Immunol Allergy Clin North Am. 2008 Feb;28(1)43-58, vi.

2. Whitcup SM. Cunningham ET jr, Ng EWM. Ed. Recent advances in ocular therapeutics. Int Ophthalmol Clin (Lippincott Williams & Wilkins). 2006; 46(4):1-6.

3. Liu G, Keane-Meyers A, Miyazadi D, et al. Molecular and cellular aspects of allergic conjunctivitis. Chem Immunol.1999;73:39-58.

4. Ono SJ, Abelson and MB. Allergic conjunctivitis: update on pathophysiology and prospects for future treatment. J Allergy Clin Immunol. 2005 Jan;115 (1):118-22.

5. Fiscella, RG and Jensen, MK. Ophthalmic Disorders. In: Young LL, ed. Handbook of Nonprescription Drugs, 16^th ed. American Pharmacists Association, Washington, DC 2009:520-543.