From the Guidelines
Diphenhydramine poisoning is a life-threatening condition that requires immediate medical attention, with treatment focusing on supportive care and management of anticholinergic symptoms. The effects of diphenhydramine poisoning can be severe, including dry mouth, blurred vision, urinary retention, tachycardia, hyperthermia, confusion, agitation, hallucinations, and potentially seizures or cardiac arrhythmias 1.
Key Considerations
- The toxic dose of diphenhydramine varies, but ingestions exceeding 7.5 mg/kg or 300 mg in adults can cause significant symptoms, with severe toxicity possible above 1,000 mg.
- Initial treatment focuses on supportive care, including airway management, intravenous fluids, and cardiac monitoring.
- For severe anticholinergic symptoms, physostigmine may be administered, but only by medical professionals in a hospital setting due to potential serious side effects.
- Activated charcoal may be given if the ingestion was recent and the patient is alert.
- Benzodiazepines like lorazepam may be used to manage agitation or seizures.
Management and Treatment
- Recovery typically occurs within 24-48 hours with appropriate supportive care.
- It is essential to call poison control or emergency services immediately if diphenhydramine poisoning is suspected.
- Medical professionals should be cautious when administering treatments, as the patient's condition can rapidly deteriorate.
- The adverse effects of diphenhydramine, as reported by Tu et al, include hypotension, dizziness, blurred vision, dry mouth, epigastric discomfort, urinary retention, and wheezing 1.
Important Notes
- Diphenhydramine has a modest stimulatory effect on ventilation and can counteract opioid-induced hypoventilation 1.
- The onset of action of diphenhydramine is several minutes, and its duration of effect is up to 4-6 hours 1.
- The hypnotic effect of diphenhydramine is increased when given in combination with alcohol or other central nervous system depressants such as benzodiazepines or opioid narcotics 1.
From the FDA Drug Label
Warnings In case of accidental overdose, get medical help or contact a Poison Control Center right away (1-800-222-1222) The effects of Diphenhydramine poisoning are not explicitly stated in the drug label, but it does mention that in case of accidental overdose, one should get medical help or contact a Poison Control Center right away 2.
- Marked drowsiness may occur
- Excitability may occur, especially in children
- It is advised to be careful when driving a motor vehicle or operating machinery due to potential drowsiness. The FDA drug label does not provide detailed information on the effects of Diphenhydramine poisoning.
From the Research
Effects of Diphenhydramine Poisoning
The effects of diphenhydramine poisoning can be severe and life-threatening. Some of the possible effects include:
- Seizures: Diphenhydramine overdose can cause seizures, as reported in several case studies 3, 4, 5, 6.
- Dysrhythmias: The overdose can also lead to dysrhythmias, including wide complex tachycardia 5, 6.
- Cardiac arrest: In severe cases, diphenhydramine poisoning can cause cardiac arrest 3, 4, 6.
- Coma: Patients may also experience coma or altered mental status 3, 4, 6.
- Respiratory failure: Diphenhydramine overdose can lead to respiratory failure, requiring intubation 6.
Treatment of Diphenhydramine Poisoning
The treatment of diphenhydramine poisoning is generally supportive, with a focus on managing the patient's symptoms and preventing further complications. Some of the treatment methods that have been reported include:
- Sodium bicarbonate: This is often used to treat sodium channel blockade caused by diphenhydramine 4, 5, 6.
- Intravenous fat emulsion: This has been used as an adjunctive therapy in some cases, due to the lipophilicity of diphenhydramine 5.
- Physostigmine: This is a traditional treatment for antihistamine overdose, but its use is not well established 7.
- Lipid emulsion therapy: This is a newer treatment that has been reported to be effective in some cases 7.
- Aggressive potassium repletion: This is important in patients with hypokalemia, as it can help to prevent cardiac arrhythmias 6.
Importance of Recognition and Treatment
It is essential for emergency physicians to be aware of the potential for diphenhydramine toxicity, especially in light of recent social media trends and the widespread availability of the medication 6. Prompt recognition and treatment of diphenhydramine poisoning can help to prevent severe complications and improve patient outcomes 3, 4, 5, 6.