Like almost every area of aviation, regulators in different countries have differing rules. Drugs also vary from country to country, and indeed some drugs which you can buy over the counter in New Zealand will get you arrested in others.
However, the rules are quite clear, and DAMEs and AMEs should not vary. For example, statins are allowed in EASA land, and all you have to do is report you are on them. However, if you are taking them because you had a heart attack, you may be grounded
regulators also like people not to fly for two weeks when starting drugs but for many substances this is mumbo jumbo and we know a lot of pilots flaunt it
I am still not sure why OP started this thread. May be he will tell us.....