Diet pills are really not very safe at all. The over-the-counter ones are the least safe. The older ones are basically speed. Some of the newer ones contain ephedra which is known to increase blood pressure and cause heart problems. Most just plain don't work. ANY medication can interact with prescribed meds...this includes over-the-counter, "natural", and "herbal". There are rx diet pills the doctor can prescribe. Even these carry risks. The only safe way to use a diet pill is with your doctor's knowledge and guidance.