Medscape – Hypersensitivity reactions, insomnia, antihistamine-specific dosing for Benadryl, Nytol (diphenhydramine), frequency-based adverse effects, … Benadryl is an OTC antihistamine used to treat a number of conditions. Taking too much can pose severe health risks, including overdose. Learn more here. 2025 The standard adult Benadryl dose is 25-50 mg every 4-6 hours, max 300 mg in 24 hours. Learn safe limits, sleep-aid doses, and when to skip … Concomitant use can increase the risk of hypotension, respiratory depression, profound sedation, coma, and death as well as urinary retention and/or severe … Benadryl overdose signs include strong drowsiness, confusion or hallucinations, extreme dryness, and fast or irregular heartbeat. What to do in … When used as a sleep aid the maximum recommended dosage is 76 mg for diphenhydramine citrate or 50 mg for diphenhydramine hydrochloride. FDA warns against taking higher than recommended doses of over-the-counter Benadryl, which can lead to serious problems and death. DESCRIPTION. Diphenhydramine hydrochloride is an antihistamine drug having the chemical name 2-(Diphenylmethoxy)-N,N-dimethylethylamine hydrochloride.