I am taking lamitogrine (Lamictil) for bipolar I...but also am taking a amphetime sytle weight loss medication (phendimentrazie....soon to change to phentermine). Will the lamicital reduce the effects of weight loss drug? these are both prescriptions, but neither doctor knows i am on the other

OH MY GOSH!! You have to be honest with your doctors! You have enough to deal with just with being Bipolar.. Medications definetly affect other medications. I would drop the weight-loss medication, because it is more important to keep your mind normal than your weight. If you want to lose weight, drop pop and try an easy exercise that you've always liked. I've had two brothers that were Bi-polar. They both took their lives because they wouldn't take medication.
Keep your chin up!

Ask your pharmacist.

antidepressants may decrease anorectic response so yes it can make the weight loss drugs less effective.

Obviously the doctors don't know about each other. No reputable physician would consider allowing you to take the two together. You pretty well deserve what you get, and you're probably hypomanic right now to think you're being smart to play this kind of game. Come clean with your shrink. You need it.