If you use MAO inhibitors (like Selegiline, Phenelzine, Furazolidone, Tranylcypromine), medications for high blood-pressure, or any other medicines for weight loss, please consult with physician before using Phentermine. Intake of stimulants which raise your blood pressure or heart rate together with Phentermine may be potentially dangerous. So if you take caffeine or decongestants regularly, address your doctor if you want to lose weight with Phentermine. Notice that decongestants are usually found in over-the-counter cold and cough medicines.