Medicines that normally reach your bloodstream in very small to moderate amounts are more likely to have significant interactions with grapefruit. This is because the effect of grapefruit can cause much larger amounts of the medicine to get into your bloodstream and cause side effects.
Safety of weight-loss drugs. Drugs for short-term use. Diethylpropion (Tenuate), phentermine (Adipex-P), benzphetamine (Didrex) and phendimetrazine are approved for only short-term use â generally less than 12 weeks. These drugs are classified as controlled substances because they have the potential to be abused.
Uses. Phentermine is used with a doctor-approved exercise, behavior change, and reduced-calorie diet program to help you lose weight. It is used by certain overweight people, such as those who are obese or have weight-related medical problems.