Reviewed on 9/14/2021

What Is Phendimetrazine and How Does It Work?

Phendimetrazine is used with a doctor-approved exercise, behavior change, and reduced-calorie diet program to help you lose weight. It is used by certain overweight people, such as those who are obese or have weight-related medical problems. Losing weight and keeping it off can lessen the many health risks that come with obesity, including heart disease, diabetes, high blood pressure, and a shorter life.

It is not known how phendimetrazine helps people to lose weight. It may work by decreasing your appetite, increasing the amount of energy used by your body, or by affecting certain parts of the brain. Phendimetrazine is an appetite suppressant and belongs to a class of drugs called sympathomimetic amines.

Phendimetrazine is available under the following different brand names: Bontril PDM.

Dosages of Phendimetrazine

Dosage Forms and Strengths

Capsules, extended release: Schedule III

  • 105 mg

Tablet: Schedule III

  • 35 mg

Dosage Considerations – Should be Given as Follows:

Possibility of addiction


  • Tablet: 35 mg every 8-12 hours 1 hour before meals
  • Range: 17.5 mg every 12 hours to 70 mg every 8 hours; not to exceed 70 mg orally every 8 hours
  • Extended release capsule: 105 mg every morning
  • Pediatric: Because pediatric obesity is a chronic condition requiring long-term treatment, the use of amphetamines approved for short-term therapy is not recommended in patients under 17 years of age


The Best Diet Tips: How to Lose Weight the Healthy Way See Slideshow

What Are Side Effects Associated with Using Phendimetrazine?

Common side effects of phendimetrazine include:

  • Abnormal heart valve findings
  • Agitation
  • Blurred vision
  • Changes in sex drive (libido)
  • Constipation
  • Diarrhea
  • Difficulty sleeping (insomnia)
  • Dizziness
  • Dry mouth
  • Euphoria
  • Fast heart rate
  • Feeling uneasy
  • Flushing (warmth, redness, or tingly feeling)
  • Headache
  • Hives
  • Hyperactivity
  • Impotence
  • Increased blood pressure
  • Nausea
  • Painful urination
  • Palpitations
  • Primary pulmonary high blood pressure (hypertension)
  • Restlessness
  • Stomach pain
  • Sweating
  • Tremors
  • Unpleasant taste
  • Upset stomach

Serious side effects of phendimetrazine include:

  • Severe headache
  • Slurred speech
  • Seizures
  • Weakness on one side of the body
  • Vision changes (e.g., blurred vision)
  • Serious (sometimes fatal) lung or heart problems (pulmonary hypertension, heart valve problems)

This is not a complete list of side effects and other serious side effects may occur. Call your doctor for information and medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088.

What Other Drugs Interact with Phendimetrazine?

If your doctor has directed you to use this medication, your doctor or pharmacist may already be aware of any possible drug interactions and may be monitoring you for them. Do not start, stop, or change the dosage of any medicine before checking with your doctor, health care provider or pharmacist first.

  • Severe interactions of phendimetrazine include:
  • Phendimetrazine has serious interactions with at least 30 different drugs.
  • Phendimetrazine has moderate interactions with at least 171 different drugs.
  • Mild interactions of phendimetrazine include:

This document does not contain all possible interactions. Therefore, before using this product, tell your doctor or pharmacist of all the products you use. Keep a list of all your medications with you, and share the list with your doctor and pharmacist. Check with your physician if you have health questions or concerns.

What Are Warnings and Precautions for Phendimetrazine?


This medication contains phendimetrazine. Do not take Bontril PDM if you are allergic to phendimetrazine or any ingredients contained in this drug.

Keep out of reach of children. In case of overdose, get medical help or contact a Poison Control Center immediately.


Effects of Drug Abuse

  • Possibility of addiction

Short-Term Effects

  • See "What Are Side Effects Associated with Using Phendimetrazine?"

Long-Term Effects

  • See "What Are Side Effects Associated with Using Phendimetrazine?"


  • Impairs ability to drive or operate heavy machinery.
  • Primary pulmonary hypertension associated with treatment.
  • Use with other anorectic agents.
  • Possibility of addiction.
  • Caution advised; increased exposure expected when administered to patients with renal impairment; excreted in urine.

Pregnancy and Lactation

  • Do not use phendimetrazine in pregnancy. The risks involved outweigh potential benefits. Safer alternatives exist.
  • Weight loss offers no potential benefit to a pregnant woman and may result in fetal harm; a minimum weight gain, and no weight loss, is currently recommended for all pregnant women, including those who are already overweight or obese.
  • Phendimetrazine use while breastfeeding is contraindicated; do not nurse if taking this drug.


Weight loss occurs in the belly before anywhere else. See Answer

Medscape. Phendimetrazine.
RxList. Bontril.

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