Can i take 75mg of diphenhydramine hci?

Depends: Diphenhydramine is the generic name of an antihistamine whose brand name is Benadryl (diphenhydramine). Drugs are usually dosed on body weight and how quickly they are usually metabolized. For this one usually every 6 hours. Most common side effect is tiredness (2 out of 3) but 1 out of 3 speed up. Never a dull moment in medicine if your always thinking about what you're doing. PS- you did not mention your weight.

Probably but why?: Adult dosing is 25-50 mg every 4-6 hours as needed. Maximum dosing is listed as 100mg per dose up to a total of 300 to 400mg per day. I'm just wondering your reason for taking 75mg, as this medicine is sedating, and can make you sleepy. If the 25-50 mg isn't strong enough, maybe there's something else better for you to try. Discuss this with your doctor, who might have a better suggestion for you.