Depending on how good your pharmacist is, I would definitely check with your pharmacist (not the tech! - they don't have the education the pharmacist does. Besides, a good tech will probably refer you to the pharmacist). It is possible, since the primary effect is on the brain/nervous system itself, that weight makes much less difference with Chantix than with some other meds (Brain is about the same weight/size in everyone), but I really don't know. If you have an excellent pharmacist, I would talk to them first. If you don't, then talk to your doc. And follow his/her recommendations.