In my several trips over there I've never encountered anything to do with drugs at all, nor have I met anyone who has (or at least no one who felt the need to mention it

). It simply doesn't seem to be part of the culture over there. Obviously that doesn't mean it doesn't exist, especially as ali47 knows people who were offered it, but it's certainly not a problem and shouldn't cause too much concern in considering Tunisia as a holiday destination.
(I've also gotten to know several Tunisians and none of them have mentioned it as either a problem there or something they indulge in)
A.x