When a person takes more than the recommended dose of diphenhydramine-containing medicine, an overdose has occurred, reports HealthCentral. Since diphenhydramine is present in several medications with different purposes, the recommended dose varies from product to product. Recommended dosage also varies based on age.
If a diphenhydramine overdose occurs, a person should promptly contact a local emergency service or the National Poison Control Center, says the U.S National Library of Medicine. A person overdosing on diphenhydramine may experience dry mouth, blurry vision and difficulty urinating, Other potential overdose symptoms include sleepiness, confusion and hallucinations.
Siphenhydramine is an antihistamine used to treat a variety of allergies as well as the common cold, according to HealthCentral. The medicine can also counteract nausea, motion sickness and insomnia. It works by blocking the body’s natural production of histamine and acetylcholine. It is not demonstrably safe or effective for children to take this medicine if they are younger than six years old. Over-the-counter products that feature diphenhydramine include Benadryl, Tylenol PM and Nytol, says the U.S National Library of Medicine.
For older people, regular use of diphenhydramine is problematic, according to The New York Times. A medical study reported in The Journal of the American Geriatrics Society in 2011 linked elderly memory loss to the regular use of diphenhydramine and other anticholinergic drugs.