Anticholinergic delirium
Diphenhydramine (Benadryl) at high doses, datura, and some prescription drugs block acetylcholine, a signalling chemical the brain and body both depend on. The result is delirium: hallucinations that feel completely real, confusion, and not knowing it is a drug effect. Mixing it with alcohol, benzos or opioids adds sedation on top of a mind that already cannot think clearly.
- Hot, dry, flushed skinNot sweating while hot is a classic sign, and it separates this from most stimulant overdoses.
- Big pupils and blurred vision
- Confusion and hallucinations, picking at clothes or at things that are not thereTalking to people who are not in the room is common.
- Unable to pee
- A racing heart, twitching, or a seizure
- 01Call 911 or Poison Control (1-800-222-1222).Diphenhydramine in overdose can cause dangerous heart rhythm problems and seizures that do not show from the outside.
- 02Do not leave them alone.Someone who is delirious does not know where they are and may walk into traffic, water or danger.
- 03Keep them somewhere cool, calm and dim.
- 04Do not give alcohol or sedatives to calm them down.That is the combination that makes this worse.
If you are going to combine anyway
- Expect it to last a long time.The mental effects can last more than 8 hours, well after the body feels normal again.
- Check what is in sleep aids and cold medicine.Diphenhydramine is in many of them, under names like ZzzQuil, Unisom and store-brand sleep aids.
- Do not combine it with other downers.
How it happens
Acetylcholine carries signals for memory and attention, and also runs the body's rest-and-digest functions: sweating, saliva, focusing the eyes, emptying the bladder, slowing the heart. Blocking it produces the whole set of signs at once, which is where the old medical rhyme comes from: hot as a hare, dry as a bone, red as a beet, blind as a bat, mad as a hatter, full as a flask.
Unlike a psychedelic, delirium does not come with the sense that it is a drug effect. People lose track of where they are and who they are with, which is why the danger is often what they do rather than the drug itself.
Street cocaine and heroin have occasionally been found cut with atropine or scopolamine, which cause the same syndrome.
Substances that carry this risk
MixSafe raises a whole-mix warning when two or more of these are in the same mix. The list is kept narrow on purpose, so it is not every drug that can contribute. Each pair still has its own rating.