Side Effects of Phentermine

Appetite suppressants may cause some serious side effects, including heart and lung problems. You and your doctor should discuss the good this medicine may do as well as the risks of taking it.

Along with its needed effects, a medicine may cause some unwanted effects. Although not all of these side effects may occur, if they do occur they may need medical attention.

Check with your doctor immediately if any of the following side effects occur:

Rare

Chest pain; decreased ability to exercise; fainting; swelling of feet or lower legs; trouble in breathing

Check with your doctor as soon as possible if any of the following side effects occur:

More common

Increased blood pressure

Less common or rare

Difficult or painful urination; fast or irregular heartbeat; feeling that others can hear your thoughts; feeling that others are watching you or controlling your behavior; hallucinations (feeling, seeing, or hearing things that are not there); headache (severe); mental depression; numbness, especially on one side of the face or body; skin rash or hives; sore throat and fever (with diethylpropion); talking, feeling, and acting with excitement and activity you cannot control; unusual bleeding or bruising (with diethylpropion)

Symptoms of overdose

Abdominal or stomach cramps; coma; confusion; convulsions (seizures); diarrhea (severe); dizziness, lightheadedness, or fainting; fast breathing; feeling of panic; fever; hallucinations (seeing, hearing or feeling things that are not there); high or low blood pressure; hostility with urge to attack; irregular heartbeat; nausea or vomiting (severe); overactive reflexes; restlessness; trembling or shaking; tiredness, weakness, and mental depression following effects of excitement

Abuse of a sympathomimetic appetite suppressant (taking the medicine in larger doses or taking it more frequently or for a longer time than the doctor ordered) can cause the following side effects:

Changes in personality; excessive, excited activity; irritability (severe); mental illness (severe), similar to schizophrenia; skin disease; trouble in sleeping (severe)

Other side effects may occur that usually do not need medical attention. These side effects may go away during treatment as your body adjusts to the medicine. However, check with your doctor if any of the following side effects continue or are bothersome:

More common

Constipation; dizziness or lightheadedness; dryness of mouth; false sense of well-being; headache; irritability; nausea or vomiting; nervousness or restlessness; stomach cramps or pain; trembling or shaking; trouble in sleeping
Note:
After the stimulant effects have worn off, drowsiness, unusual tiredness or weakness, or mental depression may occur.


Less common or rare

Blurred vision; changes in sexual desire or decreased sexual ability; diarrhea; drowsiness; frequent urge to urinate or increased urination; increased sweating; unpleasant taste

Although not all of the side effects listed above have been reported for all of these medicines, they have been reported for at least one of them. However, since all of the sympathomimetic appetite suppressants are similar, any of the above side effects may occur with any of these medicines.

After you stop using this medicine, your body may need time to adjust. The length of time this takes depends on the amount of medicine you were using and how long you used it. During this time check with your doctor if you notice any of the following side effects:

Extreme tiredness or weakness; mental depression; nausea or vomiting; stomach cramps or pain; trembling; trouble in sleeping or nightmares

Other side effects not listed above may also occur in some patients. If you notice any other effects, check with your doctor.