Phentermine is a stimulant that is similar to an amphetamine. It is an appetite suppressant that affects the central nervous system. Phentermine is used together with diet, exercise and behavioral modification to treat obesity (excessively overweight) in people with risk factors such as high blood pressure, high cholesterol, or diabetes.
Phentermine may also be used for other purposes not listed in this medication guide.
Taking Phentermine together with other diet medications such as fenfluramine (Phen-Fen) or dexfenfluramine (Redux) can cause a rare fatal lung disorder called pulmonary hypertension. Do not take Phentermine with any other diet medications without your doctor’s advice.
Phentermine can cause side effects that may impair your thinking or reactions. Be careful if you drive or do anything that requires you to be awake and alert. Avoid drinking alcohol; it can increase some of the side effects of Phentermine. Phentermine may be habit forming and should be used only by the person it was prescribed for. Keep track of how many pills have been used for each new bottle of this medicine. Phentermine is a drug of abuse, and you should be aware if any person in the household is using this medicine improperly or without a prescription.
You may have withdrawal symptoms such as depression and extreme tiredness when you stop using phentermine after a long period of use. Do not stop using Phentermine suddenly without first talking to your doctor. You may need to use less and less before you stop the medication completely.
Do not take Phentermine if you have used an MAO inhibitor such as isocarboxazid, pheneizine (Nardil), rasagiline (Azilect), selegiline (Eldepryl, Emsam), or tranylcypromine (Parnate) within the past 14 days. Serious life-threatening side effects can occur if you take phentermine before the MAO inhibitor has cleared from your body.
Do not take this medication if you are allergic to Phentermine or other stimulants. Before taking Phentermine, you should tell your doctor or nurse practitioner if you have:
It is not known whether Phentermine will harm an unborn baby. Do not take Phentermine without telling your doctor if you are pregnant. It is also not known whether Phentermine passes into breast milk or if it could harm a nursing baby. Do not take Phentermine without telling your doctor if you are breast feeding a baby. Do not give this medication to anyone younger than 16 years old without the advice of a doctor. Phentermine may be habit forming and should be used only by the person receiving the prescription. Phentermine should never be shared with another person, especially someone who has a history of drug abuse or addiction. Keep in a secure place where others cannot get to it.