Phentermine is an appetite suppressing drug that is generally prescribed for patients that are obese, with underlying health issues caused by obesity. It works by causing the hypothalamus to release norepinephrine which decreases the appetite. It also causes the release of adrenaline and epinephrine which makes the fat cells inside the body break down stored fat. Like all medications it comes with risks and side effects.

Not all people will experience the same side effects and some tolerate Phentermine very well. In general the higher dosage used will increase the risk of experiencing side effects. In clinical studies performed, one of the side effects reported was insomnia. Phentermine can act as a stimulant which can cause insomnia. Even though the exact number of patients that insomnia affects has not been reported, you should still be aware of the possibility and taking Phentermine late in the day should be avoided for this reason.

Some of the other side effects that can occur are hyperactivity and restlessness these are also due to the possible stimulating affect of Phentermine. Dry mouth, an unpleasant taste, dizziness, unusual feeling of happiness or unpleasant feelings have also been reported. Diarrhea is one of the more common side effects that people experience. If you experience loose, watery bowel movements that do not clear up in a few days you should consult your doctor. There is a potential of becoming dehydrated due to the loss of fluids and disrupting the electrolyte balance with prolonged diarrhea can be life threatening. Constipation is another possible side effect. Not being able to move your bowels can be very uncomfortable and painful. Make sure you drink plenty of fluids and increase the fiber in your diet if you become constipated. Sexual side effects also have been reported with the use of Phentermine. The loss of sex drive or changes in your sex drive are possible. Phentermine has been known to cause impotence in men. Impotence is the inability to become erect or to sustain an erection. If this happens to you, you should talk to your doctor. He or she might want to make some changes in your dosage or try another type of appetite suppressant.

There are some more serious side effects that can occur while taking Phentermine. Even though they occur less often, you should still be aware of them. These can be potentially dangerous and life threating. Pulmonary hypertension is one of the more serious possible side effects. Symptoms might include difficulty breathing, chest pain, blue lips or skin, fatigue, weakness, dizziness or fainting. Other side effects that could be serious and that should be reported to your doctor are high blood pressure and heart palpitations. A sign of an allergic reaction to Phentermine includes skin rashes, itching, hives, unexplained swelling and difficulty breathing.

You should also consult with your doctor if you are feeling increased agitation and restlessness, experiencing hallucinations, or are becoming more aggressive. Phentermine can possibly react with other medications. You should always inform you doctor of all medications you are taking. Some of the more common medications that Phentermine could react with are diabetic medications, especially insulin, MAOIs inhibitors like Parnate, Nardil, Azilect, Marplan, Eldepryl, Ensam, and Zelapar. Certain Tricyclic antidepressants can also cause a reaction. Taking these with Phentermine can increase the dangerous side effects of both of medications. They include Asendin, Elavil, Anafranil, Norpramin, Senquan, Tofanil and Tofanil PM, Pamelar Vivactil, Surmontil and Ludiomil. Phentermine has not been studied in pregnant women and therefore should not be used while you are pregnant. Taking Phentermine with certain illness can be dangerous and possibly life threatening as well. Tell your doctor if you are suffering from any illness.