Is promethazine a controlled substance?

Actually phenergan alone is not a controlled substance. When combined with codeine it is a Schedule V controlled substance.

If you are a real toxicologist then please research before posting Incorrect answer, the only time Finnigan is considered a schedule five is win it is mixed with codeine and no doctor treats nausea or vomiting with codeine

Yes, I am a real forensic toxicologist, and yes you are exactly correct. Promethazine is not a controlled substance in and of itself anywhere in the USA as far as I am aware. If mixed with a low dose of codeine, the combination is a Schedule V CS under Federal law and in most states (it's the codeine that makes it so, not the promethazine). I have not posted on Drugs.com since 2010, so I don't know where the above answer came from. Apparently someone else accessed my account somehow. I would delete the erroneous answer they posted, but there doesn't seem to be any way to do that. I have changed my login credentials in an effort to prevent anyone from using my account again. Thank you for your correction, which brought this to my attention.

It's not an antihistamine. It keeps you from vomiting.

It is both. It is an antihistamine used to treat nausea. I know that sounds odd, but it is just that.