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Fairfield, CT
203-254-0179

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Allergy Meds and Alzheimer’s

Several types of drugs used for the treatment of allergies and asthma have beneficial effects by blocking the action of histamine and other substances released during allergic reactions. However, drugs designed to treat certain symptoms rarely have pure effects and can be active on an entirely different part of the body. Side effects of the histamine-blocking drugs include a dry mouth, drowsiness, difficulty urinating, constipation, and difficulty concentrating. These side effects are termed “anticholinergic” because they are a result of blocking the involuntary or sub-conscious part of the nervous system that regulates the function of glands and organs.  For many years, the mental effects of anticholinergic drugs have been thought to be reversible. However, in the elderly, there has been a lingering suspicion that the mental effects of anticholinergic drugs are linked to dementia or Alzheimer’s disease. A new study published in the Journal of the American Medical Association has concluded there is an increased incidence of dementia in people over sixty-five with long-term use of drugs with anticholinergic properties followed over a ten-year period. The most common drug-classes cited in the study were tricyclic antidepressants, followed by first-generation antihistamine allergy drugs and drugs that prevent muscle spasms of the urinary bladder. The concern for allergy patients is the association of dementia with first generation antihistamines. The most common member of this group is Benadryl or diphenhydramine.  Others include chlorpheniramine (Chlortrimeton), hydroxyzine (Atarax), meclizine (Antivert), cyproheptadine (Periactin) and many others. Some of the newer antihistamines such as the second-generation drug fexofenadine (Allegra) do not have significant anticholinergic side effects or pass into the brain. It may be a safer long-term alternative. Cetirizine (Zyrtec) is also second-generation antihistamine, but breaks down in the body to the first-generation drug hydroxyzine. Avoid prolonged use until more data is available. One concern not addressed in the study was the dementing effect of anticholinergic drugs used to treat asthma and chronic lung disease. These include ipratropium (Atrovent), tiotropium (Spiriva) and aclidinium (Turdoza). Further study is needed for this group, who require daily usage for many years.  

If you are using any of these medications, be certain they are being used for the correct reasons. It is more common than expected to find people without allergies or asthma who have been placed on these drugs for the wrong reasons.  Steroid sprays and inhalers are alternatives to the antihistamines, but like all medications also  have unique side effects.