Diphenhydramine Overdose: Recognizing Symptoms and Emergency Response Steps

Diphenhydramine is a first-generation antihistamine developed by George Rieveschl in 1943 and approved by the FDA in 1946. Marketed under brand names including Benadryl, Tylenol PM, and Sominex, it's used for allergies, insomnia, and motion sickness. But when taken in excess, it can cause severe toxicity requiring emergency care. Every year, over 12,000 people in the U.S. end up in emergency rooms due to diphenhydramine overdose - a number that's rising, especially among teens.

Recognizing Diphenhydramine Overdose Symptoms

Diphenhydramine overdose creates a classic anticholinergic toxidrome, remembered by the mnemonic "Dry as a bone, Red as a beet, Blind as a bat, Mad as a hatter, Hot as hades, Full as a flask." Each part describes specific symptoms:

• Dry as a bone: Extremely dry mouth, throat, and skin due to reduced saliva and sweat production. This can make swallowing difficult and increase the risk of dehydration.
• Red as a beet: Flushed, warm skin from blood vessel dilation. You might notice the face and neck turning red or feeling hot.
• Blind as a bat: Dilated pupils that don't react to light, causing blurred vision. This can make it hard to see clearly or focus on objects.
• Mad as a hatter: Confusion, agitation, hallucinations, or even psychosis. People may become disoriented, see things that aren't there, or act strangely.
• Hot as hades: High fever (over 104°F/40°C) from impaired temperature regulation. This can lead to heatstroke if not treated quickly.
• Full as a flask: Urinary retention leading to a distended bladder. This often requires catheterization in the hospital.

At doses over 5 mg/kg, symptoms start to appear. For example, a 70 kg adult taking more than 350 mg could experience toxicity. Life-threatening complications like seizures (15-20% of severe cases), dangerously slow heartbeats, or cardiac arrest occur at doses exceeding 20 mg/kg (1,400 mg for a 70 kg person). The National Poison Data System 2022 report shows that over 30% of diphenhydramine overdose cases involve children under 6 accidentally ingesting the medication, often from unsecured bottles.

Immediate Emergency Steps for Diphenhydramine Overdose

If you suspect someone has overdosed on diphenhydramine, act fast. First, call the Poison Control Center immediately at 1-800-222-1222. They'll give specific instructions based on the situation. Do not try to make the person vomit - this can cause choking or further harm. If the person is conscious, keep them calm and monitor their breathing. If they're unconscious, place them on their side to prevent choking. If they're having seizures, protect their head and keep them safe until help arrives. Do not give them anything to eat or drink. Every minute counts, so get professional help right away.

Recent data shows that 68% of diphenhydramine overdoses occur in people under 20. Social media challenges like "Benadryl challenges" have driven a 300% increase in intentional overdoses among teens between 2018 and 2022. The FDA and American Academy of Pediatrics have launched campaigns to warn about these dangers. Always store medications out of reach of children and never take more than the recommended dose - even for sleep aid.

Medical Treatment for Diphenhydramine Overdose

Hospitals treat diphenhydramine overdose based on symptoms. Doctors first check vital signs, including heart rate, blood pressure, and temperature. They'll run an EKG to look for QRS widening (over 100 ms) or QTc prolongation (over 450 ms in men, 470 in women). These electrical abnormalities can lead to dangerous heart rhythms.

For seizures or severe agitation, doctors use benzodiazepines like diazepam or lorazepam. For QRS widening, sodium bicarbonate is given intravenously. This helps correct the heart's electrical activity. A 2023 study in Clinical Toxicology found that early sodium bicarbonate use reduced hospital stays by 30% in severe cases. For delirium or hallucinations, physostigmine may be used - but only if there are no heart rhythm issues. Physostigmine has a 87% success rate in reversing delirium, but it's risky for people with heart problems.

Other treatments include IV fluids for dehydration and low blood pressure, cooling blankets for high fever, and catheterization for urinary retention. In rare cases where the heart stops, extracorporeal membrane oxygenation (ECMO) may be used. The University of Virginia Poison Control Center emphasizes that "tachycardia can be quite impressive, especially if the patient is agitated," with heart rates over 140 beats per minute common in severe cases.

Preventing Diphenhydramine Overdose

Prevention starts with safe storage and education. Keep all medications locked away, especially if children are around. Read labels carefully - diphenhydramine is in many OTC products like allergy pills, sleep aids, and cold medicines. Never mix it with alcohol or other sedatives. The biggest current risk is social media challenges. Between 2018 and 2022, intentional overdoses in teens jumped 300% due to TikTok and Reddit challenges promoting dangerous doses for hallucinogenic effects. The American Academy of Pediatrics launched "Don't Take the Benadryl Challenge" to combat this. If you or someone you know is tempted to try these challenges, remember: even 300 mg can cause terrifying hallucinations and require emergency care. Real user reports describe "waking up in an ER with a catheter and IV after taking 600 mg thinking I could get high."

Smartphone apps like Poison Help (downloaded 150,000 times since 2021) provide instant access to poison control centers and first-aid guidance. The FDA has also updated warnings about diphenhydramine misuse. Always follow dosing instructions and talk to a doctor before using diphenhydramine for sleep or allergies, especially if you have heart conditions or take other medications.