Prolonged QT interval may occur due to concurrent block of potassium channels which delays repolarization, although this is less common than wide QRS. Treatment for wide QRS includes sodium bicarbonate by bolus followed by continuous infusion. If QRS is significantly prolonged, there is increased risk of ventricular arrhythmias and seizures. Wide QRS complexes indicate delayed ventricular depolarization due to sodium channel blockade. Physostigmine is not recommended for diphenhydramine toxicity by the Missouri Poison Center since it can precipitate seizures and worsen cardiac toxicity. Some physicians use the reversible cholinesterase inhibitor, physostigmine, as an antagonist of central and peripheral anticholinergic toxicity. ![]() Interference with NMDA receptor: Additive to CNS toxicity.Ĭentral anticholinergic delirium usually responds to benzodiazepines. Rhabdomyolysis: May result from intense or prolonged agitation. Tachycardia: Reduced vagal action in the heart. Wide QRS, prolonged QT: Blockade of sodium and potassium channels in the heart. “Full as a flask”: Reduced muscarinic control over the detrusor muscle in the bladder and urethral sphincter leads to urinary retention. The inactivated ciliary muscles prevent accommodation for near vision, resulting in blurred vision. “Blind as a bat”: Muscarinic block inactivates the sphincter which normally constricts the pupil, so only the radial muscle, actively pulling the pupil open, is operating. “Hot as a hare”: Rise in temperature due to decreased sweating. “Red as a beet”: Vasodilation sends blood to the skin to adjust for lack of sweating. “Dry as a bone”: Inhibition of muscarinic receptors in the sweat glands and salivary glands. “Mad as a hatter”: Inhibition of muscarinic receptors in the CNS leads to delirium, agitation, combativeness, confusion, restlessness, hallucinations, ataxia, tremor, seizures. There is also modest NMDA receptor antagonism (think PCP-like). Other overdose effects include blockade of sodium and perhaps potassium channels in the heart, which increases risk of seizures and arrhythmia. Elevated body temperature due to impaired heat dissipation is possible, especially in warm ambient environment. Ingested drugs may be more slowly absorbed, resulting in a delayed time to peak and longer course of toxicity than otherwise expected. These include tachycardia, dry flushed skin, dry mucous membranes, thick secretions, mydriasis, urinary retention, and quiet bowel. Rhabdomyolysis may result from prolonged physical agitation, particularly fighting against restraints.Ĭlassic peripheral anticholinergic symptoms may be overshadowed by the central effects. DPH crosses the blood brain barrier, accounting for the central anticholinergic syndrome of agitation, combativeness, delirium and hallucinations. Proper management is crucial because choosing the wrong treatment for certain toxic symptoms could result in fatal cardiac complications.ĭiphenhydramine is a first generation H 1-histamine receptor antagonist with prominent sedative and anticholinergic effects. The total for 2016 has nearly surpassed the total for 2015, and the year is not over yet.ĭiphenhydramine in overdose can cause significant toxicity. In subsequent years, the numbers declined by over half however, there was a 42% increase in DPH suicide gestures between 20. In 2013, there was a spike in diphenhydramine-related suicide exposures reported to the Missouri Poison Center (223 total). It is also being used more often in suicidal gestures. Unfortunately, diphenhydramine (DPH) is also abused recreationally for delirium and hallucinosis, particularly by teenagers and young adults, since it is cheap and easy to obtain. Proper management is crucial because choosing the wrong treatment for certain toxic symptoms could result in fatal cardiac complications. If someone drinks too much Benadryl ®, beware of a Diphenhydramine overdose because it can cause significant toxicity. The total for 2016 has nearly surpassed the total for 2015, and the year is not over yet. ![]() Unfortunately, the diphenhydramine (DPH) found in Benadryl ® can also be abused recreationally for delirium and hallucinosis, particularly by teenagers and young adults. It almost meets the old-fashioned definition of a cure-all. The drug comes in capsules, cough and cold preparations, and topicals. It treats allergies, itching, hives, URI symptoms, motion sickness, and insomnia. It is commonly known as Benadryl ® or Banophen ®. Diphenhydramine is a ubiquitous OTC medicine found in almost everyone’s medicine cabinet.
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