Benadryl and dementia: what to know

Benadryl is a brand name commonly associated with diphenhydramine, an antihistamine with sedating and anticholinergic effects. These effects can make a person sleepy, unsteady or less alert. In someone with dementia, a new or worse episode of confusion may be difficult to distinguish from a change in the underlying condition.

The medicine can also cause dry mouth, blurred vision, constipation and difficulty passing urine. Older adults may be particularly sensitive, and combining it with alcohol, sleeping tablets, strong pain medicines or other sedating products can increase drowsiness and falls. A new memory problem or urinary change should not automatically be blamed on dementia; a clinician can check for medicines, infection, dehydration and other causes.

Check the active ingredient and ask a pharmacist or clinician to review the complete medicine list before giving Benadryl. Some cough, cold and night-time products contain similar antihistamines, so taking more than one product can unintentionally increase the effect.

If it has already been taken, observe alertness, balance, breathing and ability to pass urine. Do not drive or leave a confused person alone near stairs or water. Arrange a medication review through a GP Consultation, especially when sleep, itching or allergy symptoms are recurring. Keep fluids available if swallowing is safe, and avoid alcohol.

Seek urgent medical help for severe or rapidly worsening confusion, inability to wake, fainting, trouble breathing, a seizure, a very fast heartbeat, or inability to pass urine with discomfort. A sudden change in memory, behaviour or walking also deserves prompt assessment, even if the person has established Dementia.

Ask which ingredient is appropriate for the symptom, whether another medicine could be contributing to confusion, and what non-drug options may help. You can also ask whether a Mental Health Assessment or medication review is suitable if sleep, anxiety or behaviour has changed.