By Medically reviewed by Hello Doktor Medical Panel


What is Adipex-P® (phentermine) used for?

Adipex-P® is a stimulant similar to an amphetamine. Phentermine is an appetite suppressant that affects the central nervous system.

Adipex-P® 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.

Adipex-P® may also be used for purposes not listed in this medication guide.

How should I take Adipex-P® (phentermine)?

Take Adipex-P® 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.

Adipex-P® can be taken with or without food.

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.

Adipex-P® should be taken only for a short time, such as a few weeks.

Do not stop using Adipex-P® suddenly, or you could have unpleasant withdrawal symptoms. Ask your doctor how to safely stop using Adipex-P®.

How do I store Adipex-P® (phentermine)?

Adipex-P® is best stored at room temperature away from direct light and moisture. To prevent drug damage, you should not store Adipex-P® in the bathroom or the freezer. There may be different brands of Adipex-P® that may have different storage needs. It is important to always check the product package for instructions on storage, or ask your pharmacist. For safety, you should keep all medicines away from children and pets.

You should not flush Adipex-P® down the toilet or pour them into a drain unless instructed to do so. It is important to properly discard this product when it is expired or no longer needed. Consult your pharmacist for more details about how to safely discard your product.

Precautions & warnings

What should I know before using Adipex-P® (phentermine)?

Before using this drug, tell your doctor if:

  • You are pregnant or breastfeeding. This is because, while you are expecting or feeding a baby, you should only take medicines on the recommendation of a doctor.
  • You are taking any other medicines. This includes any medicines you are taking which are available to buy without a prescription, such as herbal and complementary medicines.
  • You have allergy with any of active or inactive ingredients of Adipex-P® or other medications.
  • You have any other illnesses, disorders, or medical conditions.

Do not use Adipex-P® 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 Adipex-P® if you are allergic to phentermine, or if you have:

  • A history of heart disease (coronary artery disease, heart rhythm problems, congestive heart failure, stroke)
  • A history of pulmonary hypertension
  • Severe or uncontrolled high blood pressure
  • Overactive thyroid
  • Glaucoma
  • If you are in an agitated state
  • If you have a history of drug or alcohol abuse
  • If you are allergic to other diet pills, amphetamines, stimulants, or cold medications

Taking Adipex-P® 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.

To make sure you Adipex-P® is safe for you, tell your doctor if you have:

  • High blood pressure
  • Diabetes
  • Kidney disease
  • A thyroid disorder
  • If you are allergic to aspirin or to yellow food dye (FD & C Yellow No. 5, or tartrazine)

Phentermine may be habit forming. Never share Adipex-P® 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.

Is it safe during pregnancy or breastfeeding?

There are no adequate studies in women for determining risk when using Adipex-P® during pregnancy or while breastfeeding. Please always consult with your doctor to weigh the potential benefits and risks before taking Adipex-P®. Adipex-P® is pregnancy risk category X, according to the US Food and Drug Administration (FDA).

FDA pregnancy risk category reference below:

  • A=No risk
  • B=No risk in some studies
  • C=There may be some risk
  • D=Positive evidence of risk
  • X=Contraindicated
  • N=Unknown

Side effects

What side effects can occur from Adipex-P® (phentermine)?

Get emergency medical help if you have any of these signs of an allergic reaction to Adipex-P®: 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:

  • Feeling short of breath, even with mild exertion
  • Chest pain, feeling like you might pass out
  • Swelling in your ankles or feet
  • Pounding heartbeats or fluttering in your chest
  • Confusion or irritability, unusual thoughts or behavior
  • Feelings of extreme happiness or sadness
  • Dangerously high blood pressure (severe headache, blurred vision, buzzing in your ears, anxiety, chest pain, shortness of breath, uneven heartbeats, seizure)

Common side effects may include:

  • Feeling restless or hyperactive
  • Headache, dizziness, tremors
  • Sleep problems (insomnia)
  • Dry mouth or an unpleasant taste in your mouth
  • Diarrhea or constipation, upset stomach
  • Increased or decreased interest in sex, impotence

Not everyone experiences these side effects. There may be some side effects not listed above. If you have any concerns about a side-effect, please consult your doctor or pharmacist.


What drugs may interact with Adipex-P® (phentermine)?

Adipex-P® may interact with other drugs that you are currently taking, which can change how your drug works or increase your risk for serious side effects. To avoid any potential drug interactions, you should keep a list of all the drugs you are using (including prescription drugs, nonprescription drugs, and herbal products) and share it with your doctor and pharmacist. For your safety, do not start, stop, or change the dosage of any drugs without your doctor’s approval.

Products that may interact with this drug are an antidepressant–citalopram, escitalopram, fluoxetine, fluvoxamine, paroxetine, sertraline.

Does food or alcohol interact with Adipex-P® (phentermine)?

Adipex-P® may interact with food or alcohol by altering the way the drug works or increase the risk for serious side effects. Please discuss with your doctor or pharmacist any potential food or alcohol interactions before using this drug.

What health conditions may interact with Adipex-P® (phentermine)?

Adipex-P® may interact with your health condition. This interaction may worsen your health condition or alter the way the drug works. It is important to always let your doctor and pharmacist know all the health conditions you currently have.


The information provided is not a substitute for any medical advice. You should ALWAYS consult with your doctor or pharmacist before using Adipex-P® (phentermine).

What is the dose of Adipex-P® (phentermine) for an adult?

Usual Adult Dose for Weight Loss:

18.75 mg to 37.5 mg orally once a day before breakfast or 1 to 2 hours after breakfast.

In some cases it may be desirable to give half tablets (18.75 mg) two times a day.

What is the dose of Adipex-P® (phentermine) for a child?

Usual Children Dose for Weight Loss:

17 years or older:

18.75 mg to 37.5 mg orally once a day before breakfast or 1 to 2 hours after breakfast.

Adipex-P® is not recommended for use in pediatric patients under 17 years of age.

How is Adipex-P® (phentermine) available?

Adipex-P® is available in the following dosage forms and strengths:

  • Tablets, capsules: phentermine hydrochloride 37.5mg

What should I do in case of an emergency or overdose?

In case of an emergency or an overdose, call your local emergency services or go to your nearest emergency room.

What should I do if I miss a dose?

If you miss a dose of Adipex-P®, take it as soon as possible. However, if it is almost time for your next dose, skip the missed dose and take your regular dose as scheduled. Do not take a double dose.

Hello Health Group does not provide medical advice, diagnosis or treatment.

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Review Date: August 28, 2017 | Last Modified: December 19, 2019

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