Do not take phentermine if you have used an MAO inhibitor such as isocarboxazid (Marplan), phenelzine (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.
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.
Do not take this medication if you are allergic to phentermine or other stimulants, or if you have:
heart disease or high blood pressure;
arteriosclerosis (hardening of the arteries);
an overactive thyroid;
if you are in an agitated state; or
if you have a history of drug or alcohol abuse.
Before taking phentermine, tell your doctor if you are allergic to any drugs, or if you have:
problems with your thyroid,
an anxiety disorder,
epilepsy or another seizure disorder, or
If you have any of these conditions, you may not be able to use phentermine, or you may need a dosage adjustment or special tests during treatment.
It is not known whether phentermine will harm an unborn baby. Do not take phentermine without first talking to 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 first talking to 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.