Unfortunately any drug takes time and your doctor can take one of two approaches either start with the mild drugs and work up or go straight for the strongest drugs and work down if need be.(it's never simple is it) My son was diagnosed last Nov so I can understand how difficult it is firstly to come to terms with and secondly a whole world of drugs are mentioned and you do endless reading on the benefits/risks etc(all of it terrifying)
As for experience, son was initially put on asacol(like Nanners) ironically enough that gave him the big d(not one of the symptoms that he had) he was then switched to pentasa(which I believe to be another 'sister' med) Entocort was then added to the mix along with 71/2 weeks of enteral nutrition. He was still experiencing problems though so he was weaned off of entocort and put onto azathioprine(same group as 6mp) Tbh I didn't want him to move up the ladder as far as the drugs were concerned and reading all the side affects didn't help much either. The combination of azath and pentasa are working for him(did come off the pentasa for a short while but relapsed) he has gained aprox 25lb and is doing well(barr the relapse)
Side affects are scary but then if they control the symptoms and allow you to lead a relatively normal and pain free life I guess that balances any possible side affects.
Different people all appear to function better on different drugs or combination of drugs it is just about finding the right ones for you. Most drugs typically take a couple of months to kick in.
If son had a say in the matter the only drug he would not wish to go back on is the entocort(caused really bad acne) but many do not experience this.