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What Is Phentermine?

By Jacquelyn Gilchrist
Updated May 17, 2024
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Phentermine is a medication prescribed to aid in weight loss in people who are obese. It is intended to be used on a short-term basis in conjunction with a consistent exercise plan and a low-calorie diet. This drug is an appetite suppressant and a stimulant, and is classified as an anorectic.

Patients are advised to take phentermine on an empty stomach, about 30 minutes before a meal. Extended-release tablets should never be broken or chewed. The doctor may prescribe one dosage taken in the morning, or he may divide the total prescribed amount to three doses daily. It is typically not taken for longer than three to six weeks, because it can be habit-forming. Withdrawal symptoms may occur if patients suddenly discontinue using this drug.

Persistent or bothersome side effects from the use of phentermine should be reported to the prescribing physician. These may include diarrhea, vomiting, or an unpleasant taste in the mouth. Some patients may experience a dry mouth, upset stomach, and constipation.

Those who experience more serious side effects should be examined by a doctor right away. These may include dizziness, tremors, and heart palpitations. Chest pain, shortness of breath, and insomnia have also been known to occur. Some patients experience problems performing exercises that were previously within their fitness level. Others have noticed swelling of the ankles and legs, unusual thoughts or behavior, and irritability.

Phentermine may also cause a dangerously high blood pressure level. Patients who have high blood pressure should not use this drug. Signs of this side effect can include blurred vision, a severe headache, and chest pain. It can also cause uneven heartbeats, a ringing in the ears, and seizures.

Patients must be careful not to exceed the recommended dosage. An overdose of phentermine may be potentially fatal. It can cause symptoms such as hallucinations, seizures, and fainting or lightheadedness. Stomach cramps, overactive reflexes, and aggression or hostility are other possible signs of an overdose of this diet pill.

This weight loss drug should not be used by women who are pregnant or nursing. Patients must disclose all other medical conditions before taking phentermine, such as heart disease, diabetes, and thyroid disorders. A history of drug abuse, glaucoma, and arteriosclerosis may also preclude a patient from using this medicine.

Before taking phentermine, patients should disclose their other medications and supplements to their doctors. This appetite suppressant should not be combined with other diet pills, both prescription and over-the-counter, because it can cause a pulmonary hypertension, which is potentially fatal. It may also interact with insulin medications and monoamine oxidase inhibitors (MAOIs) taken in the last 14 days. In addition, patients should avoid the use of alcohol, because this may worsen side effects.

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