Whats the effect caused by sleeping pills?

Diphenhydramine - I'm 340lbs and can take 3 and go to sleep and not have any problems. From what I've read, up to 75mg or so isn't too bad. I've heard that very large doses can have some weird trippy stuff going on, but I'm not interested in that, so never tried it.

Doxylamine - A different drug, the same sleep agent that's in NyQuil. Though in a dose of Nyquil there's 6.5 or 13mg of it (can't recall if the dosing is labeled as 15ml or 30 for an adult dose) and just the pills (no cough syrup or anything else) are 25mg. As before, 2 seem to work great for me. I don't get in a fog the next day as much as with Diphenhydramine.
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