I've never tried dex, just
diphenhydramine which is nice in a very small dosage, but again makes you fall asleep right after feeling the symptoms. I had it mixed with dimenhydranate [gravol] and it was a terrible experience.
Make sure you read reports before trying anything, and "build up" your system beforehand by taking a tiny dosage one night, the next night a little more, and increasing by small dosages each time to see what you can handle so you don't have a terrible experience. I can't even take marijuana anymore because of my head's sensitivity to it.