Cross-Reaction Cautions for Asthmatic & Atopic Patients

BY WILLIAM TOWNSEND, O.D.
MAY 1997

Many of the topical and OTC oral drugs we prescribe can have profound systemic effects. Particularly at risk are patients with asthma or atopy.

ASTHMA & ATOPY OVERVIEW

Asthma is a complex condition that involves both acute and chronic inflammation. It occurs in approximately seven percent of the population, and 85 to 95 percent of individuals who have confirmed asthma are atopic, i.e., prone to allergy. Allergens, exercise, air pollution and bacterial bronchitis can trigger bronchospasm and inflammation in patients with asthma. Decreased airway lumen and plugging of the airways by mucus can lead to breathing difficulty or even death.

Management of asthma is aimed at reducing bronchospasm and inflammation. Some of the more commonly prescribed medications are epinephrine (acute attacks), inhaled beta-adrenergic agonists, theophylline, mast cell stabilizers and corticosteroids.

Atopy is the overproduction of IgE immunoglobulins in response to aeroallergens. Approximately 40 percent of the population is atopic. Atopic individuals tend to develop allergies and may be hypersensitive to ingested food or medications. When these patients suffer from a type 1 hypersensitivity reaction (acute allergy), they may go into shock or develop laryngeal edema, leading to asphyxiation and death. Treatments include antihistamines, mast cell stabilizers, corticosteroids and, in acute cases, epinephrine.

BETA-ADRENERGIC BLOCKERS

The first topical beta-blocker introduced for the treatment of glaucoma was timolol (Timoptic). Beta-blockers quickly became first choice for treating glaucoma, but they can exacerbate the symptoms of asthma because they block B2-mediated bronchodilation, thereby decreasing the lumen of the bronchial airways. Reductions of forced expiratory volume of up to 25 percent have been noted with topical 0.5 percent timolol. With the exception of betaxolol (Betoptic), a B1 selective agent, all current ophthalmic beta-blockers are nonselective.

In patients taking B1 or B2 blockers, epinephrine will not suppress an acute allergic reaction because the the beta-blocker blocks the post-synaptic receptor site. Alphagan, Trusopt and other drugs that don't cause these side effects are excellent alternatives for glaucoma patients who also have atopy and asthma.

NSAIDS

Recent studies report idiosyncratic reactions to NSAIDs, particularly aspirin, in patients with asthma. Aspirin has been shown to exacerbate asthma in up to 10 percent of patients with the disease, but it is not clear why. Patients with aspirin-induced asthma develop acute symptoms with accompanying rhinorrhea, conjunctival irritation, facial flushing and sometimes shock.

Until recently, this condition was thought to be limited to ingested NSAIDs. In a recent report, a 48-year-old asthmatic patient developed shortness of breath after beginning treatment with topical Voltaren (diclofenac sodium). Discontinuing the drops improved her condition, but her symptoms worsened after a one-drop re-challenge. During the attacks, her forced expiratory volume decreased by 65 percent. This reminds us that even "harmless" topical drops such as Voltaren can cause problems in patients predisposed to certain systemic conditions.

HISTORY REVEALS RISKS

Those of us who prescribe medications must thoroughly investigate our patients' health history. It's wise to consult an atopic patient's allergist or primary care physician before prescribing a beta-blocker. For pain or inflammation, consider drugs that rarely cross-react with aspirin. CLS

References are available via fax upon request. Call (800) 239-4684 and request document #24.

Dr. Townsend is in private practice in Canyon, Texas, and is a consultant at the Amarillo VA Medical Center.