Benefits and Risks of Popular Allergy Medications

With spring officially here, it is worth reviewing the symptoms and causes of allergies, especially allergic rhinitis, and the benefits and risks of some allergy treatments.

A person with an allergy exhibits hypersensitivity to a particular substance called an allergen. This hypersensitivity causes the body’s immune system (which defends against infection, disease and foreign bodies) to react adversely to the allergen.

If you suffer from an itchy and runny nose, watery eyes, sneezing and a tickle in the back of your throat, you probably have an allergy — in this case, from tree pollens and other spring exposures, which occur seasonally. Exposure to allergens in the air (such as pollen, dust, animal feathers or hair) can bring on these allergic symptoms. The release of a chemical in the body called histamine, triggered by your exposure to allergens, primarily causes these allergy symptoms. 

Treating the causes of an allergy

The best way to treat an allergy is to discover its cause and, if possible, to avoid that substance. If, for example, your eyes swell, your nose runs and you break out in hives each time you encounter cats, avoid cats, and you have solved your problem.

However, in many cases, avoiding the allergen is not so easy. If you sneeze during one particular season each year or year-round, there is not much you can do to avoid the pollen, dust or grass particles in the air that trigger such a reaction. Some people find relief in an indoor retreat where it is cooler, closed in and less dusty, but this is not always possible.

If you are unable to isolate and avoid the cause of your allergies, a class of drugs known as antihistamines (that work against the body’s release of histamine) is the most effective initial treatment. Many are now available over the counter.

*Another first-generation antihistamine, diphenhydramine (as in BENADRYL),
although effective, is not recommended for allergies since its sedating
properties are such that it is also sold as a sleeping pill. 

Treating the symptoms of an allergy: drugs you should not use

Unfortunately, when experiencing the effects of seasonal allergies, consumers frequently turn to over-the-counter decongestants first. However, many of these products treat only the stuffy nose — not the most prominent symptom of allergic rhinitis — and not the itchy and watery eyes, sneezing and tickle in the back of the throat.

More importantly, those decongestants that often claim to treat nasal decongestion without drowsiness actually can cause side effects such as sleeplessness, jitteriness and potential heart problems because they have amphetamine-like properties.

These products also lack the most effective treatment of seasonal allergies, antihistamines, substituting them with amphetamine-like nasal decongestants.

Some allergy products, however, combine a nasal decongestant with an antihistamine, taking the “shotgun” approach (aiming something at everything) to treating an ailment. These combination allergy products increase the risk of adverse effects and should similarly be avoided.

Treating with single-ingredient antihistamines 

Effectiveness

There is no evidence that newer, so-called second-generation antihistamines such as loratadine (the ingredient in CLARITIN, now available in generic form) are any more effective for treating allergic rhinitis than the older first-generation antihistamines such as chlorpheniramine (the ingredient in CHLORTRIMETON, now also available in generic form). (See the table for a listing of some first- and second-generation antihistamines.)

Safety: sedation and anticholinergic effects

Second-generation antihistamines claim to be less sedating than first-generation antihistamines. However, the differences between these two groups are not as striking as one would believe from their advertisements. Although first-generation antihistamines cause sedation in more patients and can interfere with driving and increase the risk of on-the-job injuries, the so-called nonsedating second-generation antihistamines still can cause sedation in 2-11 percent of patients.

All antihistamines, especially first-generation ones when taken at higher doses, can inhibit the normal functioning of acetylcholine, a ubiquitous a nervous system transmitter involved in numerous body functions. Drugs that block the effects of acetylcholine (anticholinergic drugs) can:

• cause dry mouth
• inhibit secretion of acid in the stomach
• slow the passage of food through the digestive system
• inhibit the secretion of saliva, sweat and bronchial secretions
• increase heart rate and blood pressure
• cause constipation
• cause difficulty urinating
• cause confusion and short-term memory problems

Second-generation antihistamines are not as likely as first-generation antihistamines to cause these adverse effects, which are especially troublesome for older adults. However, some studies of newer antihistamines have demonstrated a significantly increased number of people taking antihistamines and having dry mouth, for example, compared to those taking a placebo. Higher doses of these drugs can also increase the occurrence of anticholinergic adverse effects.

What You Can Do

All antihistamines, except desloratadine (CLARINEX), are available without a prescription, so you should talk to your doctor before starting any of these drugs. Consumers who believe that over-the-counter medications pose no danger compared to prescription drugs risk misuse and overdose — especially older adults, who are generally more susceptible to the side effects.

Consumers may report serious adverse events with drugs or product quality problems to the Food and Drug Administration’s (FDA’s) MedWatch Adverse Event Reporting program online or by regular mail, fax or phone.

• Online: www.accessdata.fda.gov/scripts/medwatch/medwatch-online.htm
• Regular mail: Use postage-paid, pre-addressed FDA form 3500 and mail to MedWatch, 5600 Fishers Lane, Rockville, MD 20852-9787
• Fax: (800) FDA-0178
• Phone: (800) FDA-1088