hi. wellbutrin doesn't usually cause weight gain, some people even lose weight. having said that, if you're on additional drugs, my own experience has been that drug-drug interactions can make things...unpredictable. your doctor should take that into account, of course. still, it wouldn't hurt to do one of those free, online, drugs interactions checkers. they don't pick up on everything, but they seem good about alerting people to more potentially dangerous combinations.