Diphenhydramine (Benadryl) Pharmacology

Diphenhydramine is a first generation antihistamine that is highly anticholinergic. When using medications like diphenhydramine, be sure to watch for side effects like dry eyes, dry mouth, constipation, urinary retention, and CNS changes. Sedation is a primary effect of diphenhydramine. It can be advantageous in certain situations, and detrimental in others. Drugs like donepezil, memantine, laxatives, tamsulosin, and artificial tears can be indicators of anticholinergic side effects from diphenhydramine.