This article discusses the health effects from an overdose of diphenhydramine, which is found in various over-the-counter allergy and sleep medicines.

Overdose occurs when someone accidentally or intentionally takes more than the normal or recommended amount of a drug or medication.

• Diphenhydramine

• Benadryl
• Nytol
• Sominex

• Agitation
• Blurred vision
• Coma
• Confusion
• Convulsions
• Delirium
• Diarrhea
• Drowsiness
• Dry cotton-like mouth
• Flushing on the face and skin
• Inability to urinate
• Incoherence (not understandable)
• Lack of sweat
• Low grade fever
• Movement problems
• Nausea
• Rapid heart rate
• Stomach pain
• Unsteadiness

Determine the following information:

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

However, DO NOT delay calling for help if this information is not immediately available.

The National Poison Control Center (1-800-222-1222) can be called from anywhere in the United States. This national hotline number 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.

See: Poison control center - emergency number

The health care provider will measure and monitor the patient's vital signs, including temperature, pulse, breathing rate, and blood pressure. Symptoms will be treated as appropriate. The patient may receive:

• Activated charcoal
• Tube through the mouth into the stomach to wash out the stomach (gastric lavage)

Recovery is very likely.

Wax P. Anticholinergic Toxicity. In: Tintinalli J. et al. Emergency Medicine - A Comprehensive Study Guide. 6th ed. McGraw-Hill; 2004: chap 183.