Does Benadryl Use Increase Dementia Risk?

Could older adults using anticholinergic drugs such as non-prescription sleep aids and the antihistamine Benadryl be at greater risk of developing dementia and Alzheimer’s disease? A new study suggests they may be.

A research team led by Shelly Gray, PharmD, a professor and departmental vice chair in the department of pharmacy at the University of Washington, tracked close to 3,500 men and women age 65 and older who took part in the Adult Changes in Though (ACT) study in Group Health, a Seattle-based integrated healthcare delivery system. Participants showed no dementia symptoms at the start of the study.
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Gray and colleagues used computer records from pharmacies that dispensed anticholinergic drugs to gauge the level of exposure participants had to them, adding up the standard daily doses and determining each patient’s cumulative anticholinergic exposure over the prior 10 years. The researchers updated these figures as participants were followed, for an average of 7 years.

Throughout the duration of the study, nearly 800 of the patients developed dementia, with results indicating tricyclic antidepressants such as doxepin or Sinequan, first-generation antihistamines, and anti-muscarinics for bladder control as the most commonly used medications among participants. Gray and her co-authors estimate that those taking at least 10 mg of doxepin daily, 4 mg per day of chlorpheniramine, or 5 mg daily of oxybutynin for more than 3 years would be considered at higher risk of dementia.

Primary care physicians are “advised to routinely ask older adults about over-the counter medication use, so that they can account for all anticholinergic medications used by an individual,” says Gray, adding that primary care practitioners should specifically ask about over-the-counter sleep aids and allergy medications, “because some of these products have strong anticholinergic effects.”

In addition, primary care physicians “should regularly review their older patients’ drug regimens—including over-the-counter medications—to look for chances to use fewer anticholinergic medications at lower doses,” she says.

While noting there are alternatives to anticholinergics for most conditions—including non-drug measures in some cases—healthcare providers “should use the lowest effective dose, monitor the therapy regularly to ensure it’s working, and stop the therapy if it’s ineffective,” adds Gray.

—Mark McGraw

Reference

Gray S, Anderson M, et al. Cumulative Use of Strong Anticholinergics and Incident Dementia: A Prospective Cohort Study. JAMA Intern Med. 2015