Do Antihistamines Affect Progress?

Nutrition
1

I’m taking promethazine right now for my sleep, and it’s really helping because I used to wake up multiple times at night but now even if I do wake up I can roll over and get back to sleep easily.

I was wondering if it could be affecting my efforts in the gym though, does it have any effect on these things?

2

My guess is that if you were waking up multiple times and now you can get a good nights sleep, that is more beneficial to you than any theoretical harm the drug itself could be doing in terms of muscle gain.