What is phentermine?
Phentermine is a stimulant that is similar to an amphetamine. Phentermine is an appetite
suppressant that affects the central nervous system.
Phentermine is used togther 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 other purposes not listed in this medication guide.
What should I discuss with my healthcare provider before taking phentermine?
Do not take phentermine if you have used an MAO inhibitor such as isocarboxazid
(Marplan), phenelzine (Nardil), rasagiline (Azilect), selegiline (Eldepryl, Emsam), or
tranylcypromine (Parnate) within the past 14 days. Serious, life-threatening side effects can
occur if you take phentermine before the MAO inhibitor has cleared from your body.
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 phentermine with any other diet medications without your doctor's
advice.
Do not take this medication if you are allergic to phentermine or other stimulants, or
if you have:
-
heart disease or high blood pressure;
-
arteriosclerosis (hardening of the arteries);
-
an overactive thyroid;
-
glaucoma;
-
if you are in an agitated state; or
-
if you have a history of drug or alcohol abuse.
Before taking phentermine, tell your doctor if you are allergic to any
drugs, or if you have:
If you have any of these conditions, you may need a dose adjustment
or special tests during treatment.
It is not known whether phentermine will harm an unborn baby. Do not take
phentermine without telling your doctor if you are pregnant.
It is also not known whether phentermine passes into breast milk or if it could harm a
nursing baby. Do not take phentermine without telling your doctor if you are breast-feeding a
baby.
Do not give this medication to anyone younger than 16 years old without the advice
of a doctor.
Phentermine may be habit-forming and should be used only by the person it was
prescribed for.
Phentermine should never be shared with another person, especially
someone who has a history of drug abuse or addiction.
Keep the medication in a
secure place where others cannot get to it.
How should I take phentermine?
Take this medication exactly as it was prescribed for you. Do not take the medication in
larger amounts, or take it for longer than recommended by your doctor. Follow the directions on
your prescription label.
It is best to take phentermine on an empty stomach before breakfast, or at least 10 to
14 hours before bedtime.
Do not take more phentermine for an increased effect. Taking too much
of this medication can cause serious, life-threatening side effects.
Do not crush, chew, break, or open an extended-release capsule. Swallow the pill
whole. It is specially made to release medicine slowly in the body. Breaking or opening the pill
would cause too much of the drug to be released at one time.
Phentermine should be taken only for a short time, such as a few weeks.
Taking high doses of phentermine over long periods of time can cause severe skin
problems, sleep problems (insomnia), personality changes, and feeling hyperactive or irritable.
Stop taking phentermine if you have increased hunger or if you otherwise think the
medication is not working properly.
You may have withdrawal symptoms when you stop using phentermine after a long
period of use. Do not stop using the medication suddenly without first talking to your doctor.
You may need to use less and less before you stop the medication completely.
Do not take phentermine in the evening because it may cause sleep problems (insomnia).
Store this medication at room temperature away from moisture and heat.
Keep track of how many pills have been used from each new bottle of this medicine.
Phentermine is a drug of abuse and you should be aware if any person in the household is using
this medicine improperly or without a prescription.
What happens if I miss a dose of phentermine?
Take the missed dose as soon as you remember. If it is almost time for your next dose,
skip the missed dose and take the medicine at your next regularly scheduled time.
Do
not
take extra medicine to make up the missed dose.
Where can I get more information about phentermine?
Your pharmacist has information about phentermine written for health professionals that you may read.
What are the possible side effects of phentermine?
Get emergency medical help if you have any of these
signs of an allergic
reaction:
hives; difficulty breathing; swelling of your face, lips, tongue, or throat.
Stop using phentermine and call your doctor at once if you have any of these serious
side effects:
-
feeling short of breath, even with mild exertion;
-
swelling, rapid weight gain;
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chest pain, fast or uneven heartbeat, feeling like you might
pass out;
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unusual thoughts or behavior, feeling restless or confused;
or
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dangerously high blood pressure (severe headache, blurred
vision, buzzing in your ears, anxiety, confusion, chest pain, shortness of breath, uneven
heartbeats, seizure).
Less serious side effects may include:
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feeling nervous or anxious;
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headache, dizziness, tremors;
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trouble sleeping (insomnia);
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dry mouth or an unpleasant taste in your mouth;
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diarrhea or constipation; or
-
itching.
This is not a complete list of side effects and others may occur. Tell
your doctor about any unusual or bothersome side effect. You may report side effects to FDA at 1-800-FDA-1088.
What is the most important information I should know about phentermine?
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 phentermine with any other diet medications without your doctor's
advice.
Phentermine can cause side effects that may impair your thinking or reactions. Be
careful if you drive or do anything that requires you to be awake and alert.
Avoid drinking alcohol. It can increase some of the side effects of phentermine.
Phentermine may be habit-forming and
should be used only by the person
it was prescribed for
. Keep track of how many pills have been used from each new
bottle of this medicine. Phentermine is a drug of abuse and you should be aware if any person in
the household is using this medicine improperly or without a prescription.
You may have withdrawal symptoms, such as depression and extreme tiredness, when
you stop using phentermine after a long period of use. Do not stop using phentermine suddenly
without first talking to your doctor. You may need to use less and less before you stop the
medication completely.
What should I avoid while taking phentermine?
Avoid drinking alcohol. It can increase some of the side effects of phentermine.
Phentermine can cause side effects that may impair your thinking or reactions. Be
careful if you drive or do anything that requires you to be awake and alert.
What other drugs will affect phentermine?
Before taking phentermine, tell your doctor if you are using any of the following drugs:
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medicines to treat high blood pressure;
-
insulin or diabetes medication you take by mouth;
-
guanadrel (Hylorel), guanethidine (Ismelin);
-
antidepressants such as citalopram (Celexa), escitalopram
(Lexapro), fluoxetine (Prozac, Sarafem), fluvoxamine (Luvox), paroxetine (Paxil), or sertraline
(Zoloft); or
-
antidepressants such as amitriptyline (Elavil, Etrafon),
amoxapine (Ascendin), clomipramine (Anafranil), desipramine (Norpramin), doxepin
(Sinequan), imipramine (Janimine, Tofranil), nortriptyline (Pamelor), protriptyline (Vivactil), or
trimipramine (Surmontil).
This list is not complete and there may be other drugs that can interact
with phentermine. Tell your doctor about all the prescription and over-the-counter medications
you use. This includes vitamins, minerals, herbal products, and drugs prescribed by other
doctors. Do not start using a new medication without telling your doctor.
What happens if I have an overdose of phentermine?