I took 400mg to get rid of hives, the doctor said not to surpass 300mg but I couldn't sleep with all those hives. DID not TRIP! It is an awful drug to take in those doses. Whew, I'd almost rather u do "real" drugs than OD on some crap like that which will do NOTHING for you. BTW, I was also withdrawing from opiates so no, 400mg of Unisom (same ingredient as benadryl) did NOT put me to sleep; nor did I trip, or feel "buzzed," just sick!