Phentermine

What is the most important information I should know about phentermine?
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Use caution when driving, operating machinery, or performing other hazardous activities. Phentermine may cause dizziness, blurred vision, or restlessness, and it may hide the symptoms of extreme tiredness. If you experience these effects, avoid hazardous activities.
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Phentermine is habit forming. You can become physically and psychologically dependent on this medication, and withdrawal effects may occur if you stop taking it suddenly after several weeks of continuous use. Talk to your doctor about stopping this medication gradually.
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Do not crush, chew or open any "once-daily" phentermine tablets or capsules. Swallow them whole.
What is phentermine?
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Phentermine is a sympathomimetic amine, which is similar to an amphetamine. It is also known as an "anorectic" or "anorexigenic" drug. Phentermine stimulates the central nervous system (nerves and brain), which increases your heart rate and blood pressure and decreases your appetite.
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Phentermine is used as a short-term supplement to diet and exercise in the treatment of obesity.
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Phentermine may also be used for purposes other than those listed in this medication guide.
Who should not take phentermine?
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You cannot take phentermine if you
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have heart disease or high blood pressure;
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have arteriosclerosis (hardening of the arteries);
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have glaucoma;
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have taken a monoamine oxidase inhibitor (MAOI) such as isocarboxazid (Marplan), tranylcypromine (Parnate), or phenelzine (Nardil) in the last 14 days; or
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have a history of drug or alcohol abuse.
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Before taking this medication, tell your doctor if you have
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problems with your thyroid,
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an anxiety disorder,
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epilepsy or another seizure disorder, or
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diabetes.
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You may not be able to take phentermine, or you may require a lower dose or special monitoring during treatment if you have any of the conditions listed above.
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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.
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It is also not known whether phentermine passes into breast milk. Do not take phentermine without first talking to your doctor if you are breast-feeding a baby.
How should I take phentermine?
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Take phentermine exactly as directed by your doctor. If you do not understand these directions, ask your pharmacist, nurse, or doctor to explain them to you.
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Take each dose with a full glass of water.
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Phentermine is usually taken once or twice a day before a meal on an empty stomach.
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Do not take phentermine in the evening because it may cause insomnia.
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Do not crush, chew or open any "once-daily" phentermine tablets or capsules. Swallow them whole.
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Never take more of this medication than is prescribed for you. Too much phentermine could be very dangerous to your health.
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Store phentermine at room temperature away from moisture and heat.
What happens if I miss a dose of phentermine?
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Take the missed dose as soon as you remember. However, if it is almost time for your next dose or if it is already evening, skip the missed dose and take only your next regularly scheduled dose. A dose taken too late in the day will cause insomnia. Do not take a double dose of this medication.
What happens if I overdose with phentermine?
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Seek emergency medical attention.
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Symptoms of a phentermine overdose include restlessness, tremor, rapid breathing, confusion, hallucinations, panic, aggressiveness, nausea, vomiting, diarrhea, an irregular heartbeat, and seizures.
What should I avoid while taking phentermine?
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Use caution when driving, operating machinery, or performing other hazardous activities. Amphetamine may cause dizziness, blurred vision, or restlessness, and it may hide the symptoms of extreme tiredness. If you experience these effects, avoid hazardous activities.
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Do not take phentermine late in the day. A dose taken too late in the day can cause insomnia.
What are the possible side effects of phentermine?
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If you experience any of the following serious side effects, stop taking phentermine and seek emergency medical attention:
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an allergic reaction (difficulty breathing; closing of your throat; swelling of your lips, tongue, or face; or hives);
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an irregular heartbeat or very high blood pressure (severe headache, blurred vision); or
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hallucinations, abnormal behavior, or confusion.
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Other, less serious side effects may be more likely to occur. Continue to take phentermine and talk to your doctor if you experience
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restlessness or tremor,
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nervousness or anxiety,
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headache or dizziness,
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insomnia,
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dry mouth or an unpleasant taste in your mouth,
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diarrhea or constipation, or
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impotence or changes in your sex drive.
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Phentermine is habit forming. You can become physically and psychologically dependent on this medication, and withdrawal effects may occur if you stop taking it suddenly after several weeks of continuous use. Talk to your doctor about stopping this medication gradually.
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Side effects other than those listed here may also occur. Talk to your doctor about any side effect that seems unusual or that is especially bothersome.
What other drugs will affect phentermine?
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You cannot take phentermine if you have taken a monoamine oxidase inhibitor (MAOI) such as isocarboxazid (Marplan), tranylcypromine (Parnate), or phenelzine (Nardil) in the last 14 days.
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Changes in insulin and other diabetes drug therapies may be necessary during treatment with phentermine.
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Phentermine may reduce the effects of guanethidine (Ismelin). This could lead to an increase in blood pressure. Tell your doctor if you are taking guanethidine.
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Before taking this medication, tell your doctor if you are taking a tricyclic antidepressant such as amitriptyline (Elavil), amoxapine (Asendin), doxepin (Sinequan), nortriptyline (Pamelor), imipramine (Tofranil), clomipramine (Anafranil), protriptyline (Vivactil), or desipramine (Norpramin). These drugs may decrease the effects of phentermine.
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Drugs other than those listed here may also interact with phentermine. Talk to your doctor and pharmacist before taking any prescription or over-the-counter medicines.
Where can I get more information on phentermine?
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Your pharmacist has more information about phentermine written for health professionals that you may read.