Name: Adipex-P

Phentermine Dosage

Phentermine is available in regular and orally dissolving tablets and capsules in a range of strengths, depending on the brand.

It should be prescribed at the lowest possible dosage and may depend on your condition and body weight.

Different brands of phentermine should be taken differently, but in general, phentermine is best taken on an empty stomach one hour before eating breakfast, or two hours after eating breakfast, to prevent it from interfering with your sleep.

It’s important to avoid taking it before 6:00 p.m. because it can cause problems with sleeping.

The orally disintegrating Suprenza brand can be taken with or without food.

Do not swallow the Suprenza tablet, but rather let the tablet to dissolve on your tongue.

Phentermine Overdose

If you suspect an overdose, you should contact a poison-control center or emergency room immediately.

You can get in touch with a poison-control center at (800) 222-1222.

Missed Dose of Phentermine

If you miss a dose of phentermine, try to take it as soon as you remember.

If it’s almost time for the next dose, skip the missed dose and take your next dose at the regular time.

Don't take two doses of the medication at the same time.

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.

Commonly used brand name(s)

In the U.S.

  • Adipex
  • Adipex-P
  • Atti-Plex P
  • Fastin
  • Ionamin
  • Lomaira
  • Phentercot
  • Phentride
  • Pro-Fast

Available Dosage Forms:

  • Capsule, Extended Release
  • Capsule
  • Tablet, Disintegrating
  • Tablet

Therapeutic Class: Appetite Suppressant, Centrally Acting

Chemical Class: Amphetamine Related

Uses of Adipex-P

  • It is used to treat obesity.

What do I need to tell my doctor BEFORE I take Adipex-P?

  • If you have an allergy to phentermine or any other part of Adipex-P (phentermine capsules and tablets).
  • If you are allergic to any drugs like this one, any other drugs, foods, or other substances. Tell your doctor about the allergy and what signs you had, like rash; hives; itching; shortness of breath; wheezing; cough; swelling of face, lips, tongue, or throat; or any other signs.
  • If you have ever had any of these health problems: Heart disease like heart failure or a heartbeat that is not normal, drug abuse, high blood pressure, or stroke.
  • If you have any of these health problems: Glaucoma; nervous, anxious, or tense state; or overactive thyroid.
  • If you are on dialysis, talk with your doctor.
  • If you have taken certain drugs used for low mood (depression) like isocarboxazid, phenelzine, or tranylcypromine or drugs used for Parkinson's disease like selegiline or rasagiline in the last 14 days. Taking this medicine within 14 days of those drugs can cause very bad high blood pressure.
  • If you are taking any of these drugs: Fluoxetine, fluvoxamine, paroxetine, or sertraline.
  • If you are taking or will be taking another drug like this one.
  • If you are taking any other drug (prescription or OTC, natural product) for weight loss.
  • If you are pregnant or may be pregnant. Do not take Adipex-P if you are pregnant.
  • If you are breast-feeding. Do not breast-feed while you take this medicine.

This is not a list of all drugs or health problems that interact with Adipex-P.

Tell your doctor and pharmacist about all of your drugs (prescription or OTC, natural products, vitamins) and health problems. You must check to make sure that it is safe for you to take this medicine with all of your drugs and health problems. Do not start, stop, or change the dose of any drug without checking with your doctor.

What are some side effects that I need to call my doctor about right away?

WARNING/CAUTION: Even though it may be rare, some people may have very bad and sometimes deadly side effects when taking a drug. Tell your doctor or get medical help right away if you have any of the following signs or symptoms that may be related to a very bad side effect:

  • Signs of an allergic reaction, like rash; hives; itching; red, swollen, blistered, or peeling skin with or without fever; wheezing; tightness in the chest or throat; trouble breathing or talking; unusual hoarseness; or swelling of the mouth, face, lips, tongue, or throat.
  • Signs of high blood pressure like very bad headache or dizziness, passing out, or change in eyesight.
  • Change in how you act.
  • Chest pain or pressure or a fast heartbeat.
  • A heartbeat that does not feel normal.
  • Mood changes.
  • Shakiness.
  • Shortness of breath.
  • Swelling on legs or feet.

How do I store and/or throw out Adipex-P?

  • Store at room temperature.
  • Store in a dry place. Do not store in a bathroom.
  • Keep all drugs in a safe place. Keep all drugs out of the reach of children and pets.
  • Check with your pharmacist about how to throw out unused drugs.

Drug Abuse and Dependence

Controlled Substance

Phentermine is a Schedule IV controlled substance.


Phentermine is related chemically and pharmacologically to the amphetamines. Amphetamines and other stimulant drugs have been extensively abused and the possibility of abuse of phentermine should be kept in mind when evaluating the desirability of including a drug as part of a weight reduction program.


Abuse of amphetamines and related drugs may be associated with intense psychological dependence and severe social dysfunction. There are reports of patients who have increased the dosage of these drugs to many times that recommended. Abrupt cessation following prolonged high dosage administration results in extreme fatigue and mental depression; changes are also noted on the sleep EEG. Manifestations of chronic intoxication with anorectic drugs include severe dermatoses, marked insomnia, irritability, hyperactivity and personality changes. A severe manifestation of chronic intoxication is psychosis, often clinically indistinguishable from schizophrenia.

Nonclinical Toxicology

Carcinogenesis, Mutagenesis, Impairment of Fertility

Studies have not been performed with phentermine to determine the potential for carcinogenesis, mutagenesis or impairment of fertility.

Adipex-P Food Interactions

While there are no specific Adipex-P food interactions, you should avoid drinking large amounts of beverages containing caffeine (coffee, tea, colas) or eating large amounts of chocolate while taking Adipex-P as caffeine can increase the side effects of this medicine.


Adipex-P Usage

Take Adipex-P exactly as prescribed.

Adipex-P comes in tablet and capsule. It usually taken by mouth once daily in the morning before breakfast or 1 to 2 hours after breakfast.

Taking Adipex-P in the evening can cause insomnia (trouble falling asleep or staying asleep), so Adipex-P should be taken in the morning.

Do not drink alcohol while taking Adipex-P.

If you miss a dose, take the missed dose as soon as you remember. If it is almost time for the next dose, skip the missed dose and take your next dose at the regular time. Do not take two doses of Adipex-P at the same time.

What happens if i miss a dose (adipex-p, oby-cap, suprenza, t-diet, zantryl)?

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.

Side effects

The following adverse reactions are described, or described in greater detail, in other sections:

  • Primary pulmonary hypertension [see WARNINGS AND PRECAUTIONS]
  • Valvular heart disease [see WARNINGS AND PRECAUTIONS]
  • Effect on the ability to engage in potentially hazardous tasks [see WARNINGS AND PRECAUTIONS]
  • Withdrawal effects following prolonged high dosage administration [see Drug Abuse And Dependence]

The following adverse reactions to phentermine have been identified:


Primary pulmonary hypertension and/or regurgitant cardiac valvular disease, palpitation, tachycardia, elevation of blood pressure, ischemic events.

Central Nervous System

Overstimulation, restlessness, dizziness, insomnia, euphoria, dysphoria, tremor, headache, psychosis.


Dryness of the mouth, unpleasant taste, diarrhea, constipation, other gastrointestinal disturbances.




Impotence, changes in libido.

Read the entire FDA prescribing information for Adipex-P (Phentermine Hydrochloride)

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