Can I take this diet pill with my other medications?

Since my thyroid surgery 2 years ago, I have gained 20+lbs. A month before the surgery I had a serious back injury, and am still in physical therapy with that. I am only released to walk, nothing else toward exercising. Here is my question. I am interested in taking Phendermine to help me loss the excess weight. A friend told me about it and has lost 52lbs with it. Her doctor placed her on it for one month, off the next month, back on it the third month and then took her off the pills for good after that. They watched her blood pressure during this time on the pill. I am taking Lipitor, natural hormone drops (estrogen, progesterone and DHEA,) and Armour Thyroid. Can I safely take Phendermine too?