Diphenhydramine overdose

Diphenhydramine can be harmful in large amounts.

Diphenhydramine may be found in many medicines, including those with these brand names:

• Benadryl
• Nytol
• Sominex
• Tylenol PM

Below are symptoms of a diphenhydramine overdose in different parts of the body.

BLADDER AND KIDNEYS

• Inability to urinate

EYES, EARS, NOSE, MOUTH, AND THROAT

• Blurred vision
• Dry mouth
• Enlarged pupils
• Very dry eyes
• Ringing in the ears

HEART AND BLOOD VESSELS

• Low blood pressure
• Rapid heartbeat

NERVOUS SYSTEM

• Agitation
• Confusion
• Seizures
• Delirium
• Depression
• Drowsiness
• Hallucinations (seeing or hearing things that aren't there)
• Increased sleepiness
• Nervousness
• Tremor
• Unsteadiness

SKIN

• Dry, red skin

STOMACH AND INTESTINES

• Nausea
• Vomiting

Have this information ready:

• Person's age, weight, and condition (for example, is the person awake or alert?)
• Name of the product (ingredients and strength, if known)
• Time it was swallowed
• Amount swallowed
• If the medicine was prescribed for the person

Call for help even if you don't have this information.

Your local poison control center can be reached directly by calling the national toll-free Poison Help hotline (1-800-222-1222) from anywhere in the United States. This national hotline will let you talk to experts in poisoning. They will give you further instructions.

This is a free and confidential service. All local poison control centers in the United States use this national number. You should call if you have any questions about poisoning or poison prevention. It does NOT need to be an emergency. You can call for any reason, 24 hours a day, 7 days a week.

Take the container to the hospital with you, if possible.

The health care provider will measure and monitor the person's vital signs, including temperature, pulse, breathing rate, and blood pressure.

Tests that may done include:

• Blood and urine tests
• Chest x-ray
• Electrocardiogram (ECG)

Treatment may include:

• Fluids through a vein (by IV)
• Medicines to treat symptoms or reverse the effects of the overdose
• Activated charcoal
• Laxative
• Breathing support, including a tube through the mouth into the lungs and connected to a breathing machine (ventilator)

Recovery is likely if the person survives the first 24 hours. Complications such as pneumonia, muscle damage from lying on a hard surface for a long period of time, or brain damage from lack of oxygen may result in permanent disability.

Few people actually die from an antihistamine overdose. However, serious heart rhythm disturbances may occur, which can cause death.

Keep all medicines in child-proof bottles and out of reach of children.

Benadryl overdose; Sominex overdose; Nytol overdose

Aronson JK. Anticholinergic drugs. In: Aronson JK, ed. Meyler's Side Effects of Drugs. 16th ed. Waltham, MA: Elsevier; 2016:534-539.

Eiwegger T, Simons FER, Akdis CA. Histamine and antihistamines. In: Burks AW, Holgate ST, O'Hehir RE, et al. eds. Middleton's Allergy: Principles and Practice. 9th ed. Philadelphia, PA: Elsevier; 2020: chap 92.

Hoppe JA, Monte AA. Anticholinergics. In: Walls RM, ed. Rosen's Emergency Medicine: Concepts and Clinical Practice. 10th ed. Philadelphia, PA: Elsevier; 2023:chap 140.

Updated by: Jesse Borke, MD, CPE, FAAEM, FACEP, Attending Physician at Kaiser Permanente, Orange County, CA. Also reviewed by David C. Dugdale, MD, Medical Director, Brenda Conaway, Editorial Director, and the A.D.A.M. Editorial team.