For the most part, the people losing weight here are using "old-fashioned" methods...diet and exercise. I don't know about the particular product you're referring to, but here is some information about the ingredients you mentioned.
B12 and Weight Loss - here is a really great article from the Mayo Clinic:
Vitamin B-12 Injections for Weight Loss
Lipotropics - from MedicineNet, an article by Dr. Andrew Weil
Ask the Experts: What are Lipotropics?
Adenosine isn't going to hurt you if it is genuine product (these are basically shots of ATP, the basic unit of energy in the body). There is no evidence whatsoever that they have any effect on weight loss.
Hope that helps!