Health Risks of Phentermine

Phentermine is an appetite suppressing stimulant that is similar to an amphetamine. It works on the central nervous system and the hypothalamus to affect the neurotransmitters that control hunger. Phentermine is used short term along with diet, exercise and behavior modification to help with weight loss in obese patients with a body mass higher than 30. Although it is generally well-tolerated, there are some common and serious reactions that can occur with its use.

Common Reactions

• Because it is a stimulant, phentermine can have a negative effect on the heart. Common reactions include palpitations, elevated heart rate and high blood pressure. Other physical reactions include dry mouth, constipation or diarrhea, headaches, dizziness and itching. Phentermine may also cause feelings of euphoria, restlessness, anxiety and insomnia. Some patients experience impotence or lower sex drive while taking this medication.

Serious Reactions

• Phentermine can cause some rare serious side effects that require immediate medical attention, including extreme hypertension and psychosis. Symptoms of dangerously high blood pressure include severe headache, blurred vision, confusion, chest pain, uneven heartbeats and seizures. Other signs of serious reactions are swelling, shortness of breath and unusual behavior. Phentermine can also be habit forming and cause withdrawal when discontinued.

Drug Interactions

• Taking phentermine with fenfluramine can cause a fatal lung condition called pulmonary hypertension. Fenfluramine was pulled from the market by the FDA in 1997 and is no longer widely available. Prior to the FDA ban, the two drugs were combined and sold as the weight loss medication Phen-Fen. Phentermine cannot be taken with MAO inhibitors and should not be taken with other diet medications unless under direction of your doctor. Caution should be used when combining with over-the-counter cold medications that contain pseudoephedrine or phenylephrine as these medications can increase the risk of heart-related complications.

Pre-existing Conditions

• This medication should not be used by patients with heart conditions or high blood pressure, hardening of the arteries, glaucoma or an overactive thyroid. Because it is potentially addictive, people who have a history of drug or alcohol addiction should not use it. Certain conditions may require lower doses or careful monitoring. These include anxiety disorder, diabetes and seizure disorders.

Overdose

• Do not take more than the doctor-prescribed dose of phentermine. An overdose can be fatal. Symptoms of overdose may include hallucinations, aggression, vomiting, stomach pain, shaking, confusion, hallucinations, fainting and seizures. Seek immediate medical attention if you suspect an overdose. Typical dosage is 15 to 37.5 mg per day.