It is very important that your doctor check your progress at regular visits to make sure that this medicine is working properly and does not cause any unwanted effects.
Do not use phentermine if you are also using similar medicines such as benzphetamine, diethylpropion, mazindol, phendimetrazine, Bontril®, or Didrex®. Do not use this medicine if you also take an MAO inhibitor (MAOI), such as isocarboxazid (Marplan®), phenelzine (Nardil®,), selegiline (Eldepryl®), or tranylcypromine (Parnate®), or if you have used an MAOI within the past 14 days. Using these medicines together may cause serious unwanted effects.
Using this medicine while you are pregnant can harm your unborn baby. Use an effective form of birth control to keep from getting pregnant. If you think you have become pregnant while using this medicine, tell your doctor right away.
This medicine may be habit-forming. If you think this medicine is not working properly after you have taken it for a few weeks, do not increase the dose. Instead, check with your doctor.
Call your doctor right away if you notice a decrease in your ability to exercise, or if you faint, have chest pain, swelling of your feet or lower legs, or trouble with breathing. These may be symptoms of a very serious heart or lung problem.
This medicine may cause some people to become dizzy, lightheaded, or less alert than they are normally. Make sure you know how you react to this medicine before you drive, use machines, or do anything else that could be dangerous if you are dizzy or not alert.
This medicine may affect blood sugar levels. Diabetic patients may notice a change in blood or urine sugar tests. Check with your doctor if you have any questions.
Avoid drinking alcohol while you are using this medicine.
Do not take other medicines unless they have been discussed with your doctor. This includes prescription and nonprescription (over-the-counter) medicines, dietary supplements, herbal remedies, or medicines for appetite control, asthma, colds, cough, hay fever, and sinus problems.