how much diphenhydramine is safe?
The standard dose of diphenhydramine in brand name Benadryl is 25 mg per dose for adults and 12.5 mg per dose in children's formulas. For the average healthy adult, elimination half-life ranges from 6.7 to 11.7 hours. So between 6 to 12 hours after taking Benadryl, half the drug will be eliminated from the body.