Anyone done this to lose weight?

I went to a weight loss clinic and was perscribed phentermine and CR-Nicotiante. Any of you ever used it? Did it work? Any side effects? Also they want me to go on a diet where you only take in 10 teaspoons of sugar a day. You figure how many teaspoons are in a serving by dividing the total carbs minus the dietary fiber by 5. That'll give you the amount of sugar in tsp. The other requirement is to eat 4 palm sized portions of protein a day. Is this just a fancy low-carb diet? Does this sound like a diet anyone has ever done before? Thanks.