An individual patient is always advised to consult their own physician. Correct, but, small intakes are probably ok. Zyban was initially sold as Wellbutrin. Consequently, it has been repackaged under a different name for smoking cessation.
Side effects are usually the limiting factor and tend to be headache and nausea.
Constipation and dry mouth also occur. Yes, but I would not mix these two - two very different antidepressives. Use an antihistamine like Benadryl for the time that you are on Zyban. It was found to have a helpful effect in addictive withdrawal, especially nicotine. Nausea and nightmares can occur, but less commonly.