Fastin



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Generic Name: phentermine
(FEN ter meen)

What is Fastin?

Fastin is a stimulant that is similar to an amphetamine. Phentermine is an appetite suppressant that affects the central nervous system.

Fastin 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.

Fastin may also be used for other purposes not listed in this medication guide.

What is the most important information I should know about Fastin?

Taking Fastin 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.

Fastin 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 Fastin.

Fastin 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 Fastin 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 discuss with my healthcare provider before taking Fastin?

Do not take Fastin 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 Fastin 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 Fastin 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 Fastin, tell your doctor if you are allergic to any drugs, or if you have:

  • a thyroid disorder
  • anxiety disorder
  • diabetes; or
  • epilepsy or another seizure disorder.

If you have any of these conditions, you may need a dose adjustment or special tests during treatment.

It is not known whether Fastin will harm an unborn baby. Do not take phentermine without telling your doctor if you are pregnant.

It is also not known whether Fastin 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.

Fastin 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 Fastin?

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 Fastin on an empty stomach before breakfast, or at least 10 to 14 hours before bedtime.

Do not take more Fastin 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.

Fastin should be taken only for a short time, such as a few weeks.

Taking high doses of Fastin over long periods of time can cause severe skin problems, sleep problems (insomnia), personality changes, and feeling hyperactive or irritable.

Stop taking Fastin 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 Fastin 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 Fastin 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. Fastin 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?

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.

What happens if I overdose?

Seek emergency medical attention if you think you have used too much of this medication. An overdose of Fastin can be fatal.

Overdose symptoms may include confusion, hallucinations, feeling restless or aggressive, nausea, vomiting, diarrhea, stomach pain, irregular heartbeat, tremors, rapid breathing, confusion, hallucinations, feeling light-headed, fainting, or seizure (convulsions).

What should I avoid while taking Fastin?

Avoid drinking alcohol. It can increase some of the side effects of Fastin.

Fastin 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 are the possible side effects of Fastin?

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 Fastin 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
  • chest pain, fast or uneven heartbeat, feeling like you might pass out
  • unusual thoughts or behavior, feeling restless or confused; or
  • 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:

  • feeling nervous or anxious
  • headache, dizziness, tremors
  • trouble sleeping (insomnia)
  • dry mouth or an unpleasant taste in your mouth
  • 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 other drugs will affect Fastin?

Before taking Fastin, tell your doctor if you are using any of the following drugs:

  • 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 Fastin. 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.

Where can I get more information?

Your pharmacist can provide more information about Fastin.


Remember, keep this and all other medicines out of the reach of children, never share your medicines with others, and use this medication only for the indication prescribed

Every effort has been made to ensure that the information provided by Cerner Multum, Inc. ('Multum') is accurate, up-to-date, and complete, but no guarantee is made to that effect. Drug information contained herein may be time sensitive. Multum information has been compiled for use by healthcare practitioners and consumers in the United States and therefore Multum does not warrant that uses outside of the United States are appropriate, unless specifically indicated otherwise. Multum's drug information does not endorse drugs, diagnose patients or recommend therapy. Multum's drug information is an informational resource designed to assist licensed healthcare practitioners in caring for their patients and/or to serve consumers viewing this service as a supplement to, and not a substitute for, the expertise, skill, knowledge and judgment of healthcare practitioners. The absence of a warning for a given drug or drug combination in no way should be construed to indicate that the drug or drug combination is safe, effective or appropriate for any given patient. Multum does not assume any responsibility for any aspect of healthcare administered with the aid of information Multum provides. The information contained herein is not intended to cover all possible uses, directions, precautions, warnings, drug interactions, allergic reactions, or adverse effects. If you have questions about the drugs you are taking, check with your doctor, nurse or pharmacist.