Poisoning began above 0.3 g, six times a night's sleep-aid dose
Across 282 single-drug poisonings, agitation, confusion and hallucinations appeared above 0.3 g at once. Delirium, seizures and coma appeared above 1.0 g.
What the study found
Poisoning symptoms begin at about six times a sleep-aid dose
Across 282 single-drug diphenhydramine poisonings, agitation, confusion and hallucinations appeared above 0.3 g at once, six times the 50 mg a sleep-aid box allows in a night. Delirium, seizures and coma appeared above 1.0 g, and the centre advised hospitalising anyone above that.
The caveat · Only poisonings someone phoned in
These are calls to a poison centre, so mild poisonings nobody phoned about are missing and the mix looks worse than all ingestions would. The amount swallowed is what someone reported afterwards, unreliable in both directions. Above 1.5 g, coma and seizures grew more common while delirium did not.