MODERATE — Monitor Closely
CAUTION — additive anticholinergic burden, especially dangerous in elderly
Evidence level: STRONG
Taking two anticholinergic antihistamines together greatly increases side effects like dry mouth, urinary retention, and confusion.
Additive anticholinergic effects. Both are first-generation antihistamines with strong anticholinergic properties.
Do not combine two anticholinergic antihistamines. Use one or switch to a non-anticholinergic option.
Take Hydroxyzine and Diphenhydramine as prescribed by your healthcare provider. If both are taken daily, maintain consistent timing for each. Many medications compete for the same liver enzymes (CYP450 system). Your pharmacist can advise whether spacing these apart would improve efficacy.
Elderly (dementia risk), benign prostatic hyperplasia, glaucoma, concurrent anticholinergic medications
Dry mouth, blurred vision, urinary retention, constipation, confusion, tachycardia, delirium in elderly
Review total anticholinergic burden with pharmacist. Beers Criteria flags both in elderly.
Discuss safer alternatives with your healthcare provider. They can recommend substitutions based on your specific health goals while minimizing interaction risks. Always bring a complete list of everything you take to your appointments.
Taking two anticholinergic antihistamines together greatly increases side effects like dry mouth, urinary retention, and confusion.
Take Hydroxyzine and Diphenhydramine as prescribed by your healthcare provider. If both are taken daily, maintain consistent timing for each. Many medications compete for the same liver enzymes (CYP450 system). Your pharmacist can advise whether spacing these apart would improve efficacy.
Dry mouth, blurred vision, urinary retention, constipation, confusion, tachycardia, delirium in elderly
Discuss safer alternatives with your healthcare provider. They can recommend substitutions based on your specific health goals while minimizing interaction risks. Always bring a complete list of everything you take to your appointments.
Review total anticholinergic burden with pharmacist. Beers Criteria flags both in elderly.
Or browse the full interaction database (121,000+ pairs).