anti-cholinergics, like diphenhydramine, taken in excess, will make you trip hard. Unpleasantly hard. Balls-out conversations with trees that have lips and spider-legs tripping.
It is dangerous and scary.
Unfortunately, a lot of anti-psychotics have anti-cholinergic side effects.
It's also responsible for "drying you out"--that is, cotton mouth, red eyes; I think the lack of sweat can cause over-heating too.
And yes, sometimes heart palpitations.
(And yes, time stops. I can still remember closing the patio door behind me and it took what felt like two hours. And I looked across the lawn and the neighbors TV antenna was a giant daddy-long legs, like ten feet tall, spindly legs weaving a web. The next day I noticed my neighbors haven't had a TV antenna since the 1980's.)