Will 7800 mg of diphenhydramine kill you?

Answer 1

Theoretically it could, but you would have to take an EXTREMLEY large dose. The LD50 of diphenhydramine (the rate at which 50% of mice die when the medicine is ingested) is about 500mg, or about 20 pills per kilogram of body weight.

Answer 2

I'd strongly advise against it. Although I doubt it would be fatal unless you were ill or weak like a newborn or elderly. It will increase unpleasant hallucinations at doses as high as 500mg so 7800mg would cause horrible abdominal pains, vomitting and your nose will feel aweful since diphenhydramine is an antihistamine (helps you breathe).