If you are taking Wellbutrin or Topamax against prescription for weight loss, then my sincere advice is to stop it and go for weight loss the healthy way through diet control and exercise. However, if your doctor has prescribed Topamax for short term use to initiate weight loss (the only weight loss indication it has been approved of by FDA, to be taken along with exercise and diet control), then please continue it as asked by your doctor. Similar is the story with Wellbutrin.
Both the drugs cause weight loss as a side effect and hence should be taken for short time to initiate weight loss. Meanwhile change your diet habits and improve your exercise levels.
People have lost about 10-12 kg by this method, but under strict supervision of a doctor.
The medical advice given should not be considered a substitute for medical care provided by a doctor who can examine you. The advice may not be completely correct for you as the doctor cannot examine you and does not know your complete medical history. Hence this reply to your post should only be considered as a guiding line and you must consult your doctor at the earliest for your medical problem.