"the reasons teenagers give for trying drugs and what you can say"

Unless you're too busy having conniptions, that is. I had a laugh with my folks today over John Howard's "Tough on Drugs!" promotional booklet which we all received in the post lately. I don't know about your family dynamics when you were a teenager, but parental conniptions were a feature of ours. If I'd dared to pipe up with, "I always wanted to try that stuff!" or maybe even "It made me feel really good!" when busted, I'd only have earnt myself a good ohrfeige*. And, surely, had my ass grounded from here to kingdom come.
At least we can look back and laugh, I guess.
Talking to your kids about drugs is all well and good advice and probably worth the price of this attractive booklet. Just don't expect them to tell you the truth. Unless they're stupid.

*Ohrfeige: German. Literally ear-fig, but (from memory) equates to getting your ears boxed.