Phentermine is a stimulant similar to an amphetamine. It acts as an appetite suppressant by affecting the central nervous system.
Phentermine is used together with diet and exercise to treat obesity (overweight) in people with risk factors such as high blood pressure, high cholesterol, or diabetes.
Phentermine may also be used for purposes not listed in this medication guide.
Important information
Do not use phentermine if you are pregnant or breast-feeding a baby.
You should not take phentermine if you have a history of heart disease (coronary artery disease, heart rhythm problems, congestive heart failure, stroke), severe or uncontrolled high blood pressure, overactive thyroid, glaucoma, a history of pulmonary hypertension, if you are in an agitated state, or if you have a history of drug or alcohol abuse.
Do not use phentermine if you have taken an MAO inhibitor in the past 14 days. A dangerous drug interaction could occur. MAO inhibitors include isocarboxazid, linezolid, phenelzine, rasagiline, selegiline, and tranylcypromine.
Before taking this medicine
Do not use phentermine if you have taken an MAO inhibitor in the past 14 days. A dangerous drug interaction could occur. MAO inhibitors include isocarboxazid, linezolid, phenelzine, rasagiline, selegiline, and tranylcypromine.
You should not take phentermine if you are allergic to it, or if you have:
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a history of heart disease (coronary artery disease, heart rhythm problems, congestive heart failure, stroke);
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a history of pulmonary hypertension;
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severe or uncontrolled high blood pressure;
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overactive thyroid;
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glaucoma;
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if you are pregnant or breast-feeding;
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if you are in an agitated state;
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if you have a history of drug or alcohol abuse; or
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if you are allergic to other diet pills, amphetamines, stimulants, or cold medications.
Taking phentermine together with other diet medications such as fenfluramine (Phen-Fen) or dexfenfluramine (Redux) can cause a rare fatal lung disorder called pulmonary hypertension. Do not take this medicine with any other diet medications without your doctor"s advice.
To make sure you phentermine is safe for you, tell your doctor if you have:
Phentermine may be habit forming. Never share phentermine with another person, especially someone with a history of drug abuse or addiction. Keep the medication in a place where others cannot get to it.
FDA pregnancy category X. Weight loss during pregnancy can harm an unborn baby, even if you are overweight. Do not use phentermine if you are pregnant.
See also: Pregnancy and breastfeeding warnings (in more detail)
Phentermine can pass into breast milk and may harm a nursing baby. You should not breast-feed while taking this medicine.
Do not give this medication to a child younger than 16 years old.
How should I take phentermine?
Take phentermine exactly as prescribed by your doctor. Follow all directions on your prescription label. Do not take this medicine in larger or smaller amounts or for longer than recommended.
Some brands of phentermine should be taken on an empty stomach before breakfast or within 2 hours after breakfast.
Suprenza disintegrating tablets can be taken with or without food.
Using dry hands, remove the Suprenza tablet from the medicine bottle and place the tablet in your mouth. It will begin to dissolve right away. Do not swallow the tablet whole. Allow it to dissolve in your mouth without chewing.
To prevent sleep problems, take this medication early in the day, no later than 6:00pm.
Talk with your doctor if you have increased hunger or if you otherwise think the medication is not working properly. Taking more of this medication will not make it more effective and can cause serious, life-threatening side effects.
Phentermine should be taken only for a short time, such as a few weeks.
Do not stop using phentermine suddenly, or you could have unpleasant withdrawal symptoms. Ask your doctor how to safely stop using this medicine.
Store at room temperature away from moisture and heat.
Keep track of the amount of medicine used from each new bottle. Phentermine is a drug of abuse and you should be aware if anyone is using your medicine improperly or without a prescription.
What happens if I miss a dose?
Take the missed dose as soon as you remember. Skip the missed dose if it is almost time for your next scheduled dose. Do not take extra medicine to make up the missed dose.
What happens if I overdose?
Seek emergency medical attention or call the Poison Help line at 1-800-222-1222. An overdose of phentermine can be fatal.
What should I avoid?
Drinking alcohol can increase certain side effects.
Phentermine may impair your thinking or reactions. Be careful if you drive or do anything that requires you to be alert.
Phentermine side effects
Get emergency medical help if you have any of these signs of an allergic reaction to phentermine: hives; wheezing, chest tightness, trouble breathing; swelling of your face, lips, tongue, or throat.
Call your doctor at once if you have a serious side effect such as:
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feeling short of breath, even with mild exertion;
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chest pain, feeling like you might pass out;
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swelling in your ankles or feet;
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pounding heartbeats or fluttering in your chest;
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confusion or irritability, unusual thoughts or behavior;
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feelings of extreme happiness or sadness; or
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dangerously high blood pressure (severe headache, blurred vision, buzzing in your ears, anxiety, chest pain, shortness of breath, uneven heartbeats, seizure).
Common phentermine side effects may include:
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feeling restless or hyperactive;
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headache, dizziness, tremors;
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sleep problems (insomnia);
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dry mouth or an unpleasant taste in your mouth;
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diarrhea or constipation, upset stomach; or
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increased or decreased interest in sex, impotence.
This is not a complete list of side effects and others may occur. Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088.
See also: Side effects (in more detail)
Phentermine dosing information
Usual Adult Dose for Weight Loss:
15 to 37.5 mg orally once a day before breakfast or 1 to 2 hours after breakfast.
Usual Pediatric Dose for Weight Loss:
17 years or older:
15 to 37.5 mg orally once a day before breakfast or 1 to 2 hours after breakfast.
What other drugs will affect phentermine?
Taking this medicine with other stimulant drugs that make you restless or hyperactive can worsen these effects. Ask your doctor before taking phentermine with diet pills, other stimulants, or medicine to treat attention deficit hyperactivity disorder (ADHD).
Tell your doctor about all medicines you use, and those you start or stop using during your treatment with phentermine, especially:
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an antidepressant--citalopram, escitalopram, fluoxetine, fluvoxamine, paroxetine, sertraline.
This list is not complete. Other drugs may interact with this medicine, including prescription and over-the-counter medicines, vitamins, and herbal products. Not all possible interactions are listed in this medication guide.
