What should you know about diphenhydramine and dementia?

Diphenhydramine is an antihistamine with sedating and anticholinergic effects. These can cause sleepiness, blurred vision, dry mouth, constipation, difficulty passing urine and impaired coordination. In a person with dementia, a new or increased level of confusion can be difficult to distinguish from a change in the underlying condition. Sedation can also increase falls risk and make it harder to notice illness. Read more about Dementia and Memory Problems.

Do not start diphenhydramine for sleep, allergy symptoms, cough or cold symptoms without checking the full medicine list with a pharmacist or prescriber. Do not stop a regular prescribed medicine suddenly unless advised. Record when symptoms began, the product name and strength, and any change in alertness, walking, urination or behaviour. Non-drug approaches may be considered depending on the reason for treatment. A GP Consultation can help review the cause and alternatives.

Seek urgent medical help for sudden severe confusion, inability to wake the person, collapse, a seizure, difficulty breathing, new weakness, or inability to pass urine with lower abdominal pain. A rapid change in thinking or behaviour needs assessment because infection, dehydration, medicine effects and other problems can look alike. Contact a clinician promptly after a new dose if the person becomes unusually sleepy, unsteady, agitated or confused.

Ask what symptom is being treated, whether diphenhydramine interacts with current medicines, and which alternative has less sedating or anticholinergic effect. Ask how to monitor alertness, balance, bowel movements and urination.