I'm a sucker for google lol. This is what I found so far as drug interactions. I think maybe you were looking for people specifically taking chantix and met so I can't help you there. I also wanted to say good luck

My sister is starting chantix on Nov 1st. I hope the best for you!!
Drug-Drug Interactions
Drug interaction studies were performed with varenicline and digoxin, warfarin, transdermal nicotine, bupropion, cimetidine and
metformin. No clinically meaningful pharmacokinetic drug-drug interactions have been identified.