Approximately 20% of the general population is affected by allergic rhinitis, a systemic allergic disease characterized by episodes of sneezing, itching, rhinorrhea, and nasal obstruction.(1) Timing and duration distinguish perennial allergic rhinitis from seasonal allergic of symptoms distinguish perennial allergic rhinitis from seasonal allergic rhinitis.(2) The former is characterized by symptoms that persist throughout the year without a seasonal pattern, whereas seasonal allergic rhinitis is defined by seasonal symptoms that are repetitive and predictable.(2,3) The general treatment strategy is a stepwise approach that includes allergen avoidance, phar-macotherapy, and immunotherapy for specific antigens. Because there is no cure for allergic rhinitis, treatment should be individualized to provide symptomatic relief and improve functional status, while minimizing adverse effects. The pharmacist can play an integral role in maximizing desired outcomes through appropriate drug selection and effective patient counseling.
Pharmacotherapy primarily consists of agents with antihistamine, decon-gestant, anticholinergic, or mast-cell stabilizing properties. (2,4)Although a number of effective medications are available by prescription, many patients will seek symptomatic relief with OTC medications or a combination of both. A variety of OTC medications are available that treat the symptoms of allergic rhinitis, and patients will likely try these initially, because they are easily accessible. In addition, patients with allergic rhinitis who are reluctant to seek medical advice from a prescriber and patients who do not have health insurance can be expected to self-medicate with OTC products. Therefore, a thorough knowledge of nonprescription therapy is crucial to effectively counsel patients.
Antihistamines are the most commonly prescribed medication for the treatment of allergic rhinitis.(5)They exert their effect by competitive inhibition of histamine at its receptor site. These agents provide symptomatic relief for itching, sneezing, and rhinorrhea but have little effect on nasal congestion. Antihistamines are distinguished by receptor specificity and the rapidity and degree to which they penetrate the blood-brain barrier. In general, this class can be divided into first-generation (nonselective, sedating) and second-generation (selective, nonsedating) agents.(2) More recently, a third group has emerged: third-generation agents are metabolites of second-generation antihistamines and may show improvements in cardiac effects.(5) Currently, only first-generation antihistamines are available without a prescription.
First-generation antihistamines readily cross the blood-brain barrier, where they bind not only to histamine receptors, but also to dopami-nergic, serotonergic, and cholinergic receptors. Therefore, these agents carry significant central nervous system (CNS) and anticholinergic side effects. These side effects include drowsiness, fatigue, dizziness, impairment of cognition, dry mouth, dry eyes, dry nose, constipation, urinary hesitancy or retention, and precipitation of narrow angle glaucoma.(2,5) Of this group of antihistamines, the ethanolamines, such as diphenhy-dramine, doxylamine, and phenyl-toloxamine, are the most sedating. The alkylamines, such as brompheni-ramine, chlorpheniramine, and pheniramine, are the least sedating, but are not free of adverse effects.(2)
It is important to counsel patients about potential side effects. Driving performance, work performance, coordination, motor skills, and information processing can be adversely affected with these agents. First-generation antihistamines add to the CNS depressant effects of other drugs and alcohol. In addition, because their drying effects on secretions can lead to mucous plugging, these antihistamines also carry warnings for patients with asthma. They are contraindicated for patients with stenosing peptic ulcer, symptomatic prostatic hypertrophy, bladder neck obstruction, or pyloroduodenal obstruction, and for patients taking monoamine oxidase inhibitors. They may also cause photosensitization; patients should be advised to wear protective clothing and use sunscreens. Instruct patients to use antihistamines within 3 to 5 hours of anticipated exposure to an allergen or on a regular basis for long-term therapy.(2)
Second- and third-generation antihistamines are large, lipophilic molecules that act rapidly and exhibit poor CNS penetration. Therefore, they lack significant anticholinergic side effects, rarely cause drowsiness, and do not impair cognitive function. These agents are advantageous in many situations and should be recommended in patients who cannot tolerate the side effects of the sedating antihistamines or whose medical condition or lifestyle does not permit the use of these agents. They do require a prescription, however. The pharmacist can play an integral role in educating a patient about the differences and advising the patient to see a physician. It should be noted that regulators have approved the sale of at least one second-generation antihistamine, loratadine, without prescription; it is expected that this agent will be available to consumers in late 2002.
Decongestants are alpha-adrenergic agonists that reduce nasal congestion and, to some extent, rhinorrhea. They have no effect on symptoms such as sneezing and itching, or on ocular symptoms, but they are often used in combination with antihistamines when nasal obstruction is an issue. The most common side effects of decon-gestants include CNS effects such as nervousness, insomnia, irritability, and headache, as well as cardiac effects such as palpitations and tachycardia. Decongestants can be associated with increased blood pressure, worsening urinary retention, and elevated blood glucose.(2,3,6)
Pseudoephedrine is one of the most commonly used decongestants. Phenylpropanolamine has also been used extensively; however, the FDA has taken steps to remove it from all drug products because of an increased risk of hemorrhagic stroke. It is a good idea to remind patients to remove any old products containing phenyl-propanolamine from their medicine cabinets.
Topical intranasal decongestants are available OTC as well and continue to be widely used by many people. Although these agents are applied topically and do not cause systemic side effects, they should not be used for longer than 3 to 5 days. Patients using these agents for longer periods of time may suffer from rhinitis medicamen-tous, or rebound congestion, after withdrawal.(5,6)
Cromolyn is another nonprescrip-tion medication for allergic rhinitis. This drug stabilizes mast cells, reducing the release of histamine and other mediators. It is effective for immunologic triggers and non?immune-mediated triggers, such as chemicals, cold air, or exercise.(2,6) Cromolyn is administered topically; the recommended dose is 1 spray in each nostril 3 to 6 times daily at regular intervals. It may take 3 to 7 days to initially see benefit and up to 2 to 4 weeks of continued therapy before maximal benefit is observed.(2) Because <7% of the drug is absorbed systemically, side effects are rare. The most common include sneezing, nasal stinging, and burning. The usefulness of cromolyn is often limited because of the need for frequent dosing. It may be most beneficial when used as a pro-phylactic treatment before an anticipated allergen exposure or in patients whose medical conditions do not allow the use of other medications, eg, pregnancy.
Nasal Wetting Agents
Saline, propylene, and polyethylene glycol sprays may decrease nasal stuffiness, rhinorrhea, and sneezing by relieving nasal mucosal irritation.(2) For the patient with dried, encrusted, or thick mucus, these agents can help in its removal. No significant side effects have been noted; therefore, these agents are safe in patients with medical conditions that preclude them from using other pharmacologic therapies.
In addition to helping patients distinguish the numerous OTC drug therapies available, the pharmacist can also play an important role in encouraging patients to see a physician when necessary and providing important counseling points. Like the nonsedating antihistamines, other pharmacologic agents for the treatment of allergic rhinitis, such as intranasal corticosteroids, ipratropi-um, and leukotriene modifiers, are available by prescription only. All of these agents are beneficial in various patient populations suffering from allergic rhinitis. Better side-effect profiles and improved efficacy of various products may be advantageous; patients should be encouraged to seek medical advice from a physician in these situations.
Patients choosing to self-medicate may not know the importance of allergen avoidance in the stepwise approach to managing this disease state. Pharmacists should advise patients that allergen avoidance is the primary nonpharmacologic intervention for allergic rhinitis. It is important to keep in mind that avoidance depends on the specific antigen. Some general points include the following (2):
? Remove environmental dust (eg, remove carpets, upholstered furniture, stuffed animals, bookshelves).
? Encase mattresses, box springs, and pillows with mite-impermeable materials.
? Wash bedding at least weekly in hot (130?F) water.
? Avoid activities that disturb decaying plant material (eg, raking leaves).
? Lower household humidity.
? Remove houseplants.
? Vent food preparation areas and bathrooms.
? Repair damp basements.
? Frequently apply fungicide to moldy areas.
? Remove cats from the indoor environment or bathe them weekly.
? Avoid outdoor activities when pollen counts are high.
? Use high-efficiency particulate air (HEPA) filters to remove pollen, mold spores, and cat allergens (will not remove fecal particles from house dust mites).
With so many people affected by allergic rhinitis and the availability of nonprescription drug therapy to treat the symptoms, it is likely that the pharmacist will encounter patients seeking advice about self-medicating or using OTC products in combination with prescription therapies. Not only can pharmacists help patients distinguish between products, but they can also be instrumental in guiding patients to seek medical advice from a physician if needed. In addition, effective counseling will help patients maximize therapy for optimal benefit.
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