Phendimetrazine (Bontril) is an anorectic drug similar to amphetamines. It suppresses appetite and increases the metabolic rate. It is used in the management of exogenous obesity as an adjunct to diet and exercise.

Phendimetrazine Uses:

• Obesity:

  • It is used in the management of obesity as a short-term treatment in adjunct to a low caloric diet and exercise.

Phendimetrazine (Bontril) Dose in Adults

Phendimetrazine (Bontril) Dose in the short-term treatment of Obesity: Oral:

• Extended-release:

  • 105 mg once a day 30 to 60 minutes before the first meal of the day.

• Immediate-release:

  • 35 mg twice or thrice daily, one hour before meals. Some patients may require a lower dose (one-half tablet or 17.5 mg per dose).
  • The maximum dose should not exceed 70 mg thrice daily.

Phendimetrazine (Bontril) Dose in Children:

Refer to adults dosing.

Pregnancy Risk Factor X/C

• It has not yet been tested in human or animal pregnancies.
• It is contraindicated during pregnancy because of its potential to cause harm and lack of benefits.
• While obesity can be linked to increased maternal and fetal outcomes during pregnancy, it is not recommended that you take medication to lose weight.

Use during breastfeeding:

• It is unknown if the drug is excreted from breastmilk. After maternal intake, amphetamines were detected in breastmilk.
• Manufacturers recommend that you avoid it while breastfeeding. Before discontinuing drug therapy or breastfeeding, it is important to weigh the risks and benefits.

Dose in Kidney Disease:

• There are no dosage adjustments provided in the manufacturer's labeling as it has not been studied in patients with kidney disease.
• However, it should be used with caution in patients with kidney disease as it is excreted via the kidneys.

Dose in Liver Disease:

There are no dosage adjustments provided in the manufacturer's labeling.

Side effects of Phendimetrazine (Bontril):

• Cardiovascular:

  • Flushing
  • Hypertension
  • Ischemic Events
  • Palpitations
  • Tachycardia
  • Valvular Disease (Regurgitant)

• Central Nervous System:

  • Agitation
  • Dizziness
  • Headache
  • Insomnia
  • Overstimulation
  • Psychosis
  • Restlessness

• Endocrine & Metabolic:

  • Changes In Libido

• Gastrointestinal:

  • Constipation
  • Diarrhea
  • Nausea
  • Stomach Pain
  • Xerostomia

• Genitourinary:

  • Dysuria
  • Urinary Frequency

• Neuromuscular & Skeletal:

  • Tremor

• Ocular:

  • Blurred Vision
  • Mydriasis

• Respiratory:

  • Primary Pulmonary Hypertension

• Miscellaneous:

  • Diaphoresis
  • Tachyphylaxis

Contraindications to Phendimetrazine (Bontril):

• Allergies or idiosyncrasies to phendimetrazine or other sympathomimetic anti-amines or any component of formulation
• Glaucoma;
• Patients who are unable to speak or are agitated;
• Patients who have a history of drug abuse
• Hyperthyroid states;
• Coadministration with CNS or anorectic stimulant drugs
• Within 14 days of monoamine oxidase inhibitors treatment.

Additional contraindications Extended-release

• Patients who have had a history of heart disease (e.g., cardiac arrhythmias or heart failure), uncontrolled hypertension, hypertension, pulmonary hypertension and stroke).
• pregnancy;
• Breast-feeding

Instant-release

• Patients with advanced arteriosclerosis, symptomatic heart disease, and patients with severe and moderate hypertension.

Warnings and precautions

• CNS depression:

  • It can cause impairment of the central nervous system. It should be used with caution by patients who are required to drive or operate heavy machinery.

• Heart failure:

  • According to the AHA, the drug is known to cause myocardial damage. Patients with heart disease should avoid it.

• Hypertension in the lungs:

  • Rarely, pulmonary hypertension can be fatal. The treatment should not last more than three months.
  • Patients with shortness of breath, unexplained syncope, lower extremity swelling, chest pain, and/or angina should stop receiving treatment immediately. They should also be checked for pulmonary hypertension.

• Heart disease of the valvular kind:

  • Patients with valvular disease of the heart or known cardiac murmurs should not use it.
  • Preexisting valvular disease may be exacerbated by anorectic drugs. Patients who use the drug for an extended period of time or take higher doses than usual, as well as those who are taking the drug with concomitant anorectic medications, are at greater risk of experiencing cardiac adverse events.

• Diabetes:

  • Diabetes mellitus patients should be cautious when using the drug. The drug's anorexic qualities can cause hypoglycemia in patients with diabetes mellitus.

• Hypertension:

  • Patients with angina, hypertension, and other cardiovascular conditions should be cautious about taking the drug. It may increase blood pressure or worsen existing cardiac disease.

• Renal impairment

  • Patients with impaired renal function should be cautious when taking the drug.

• Seizure disorders:

  • Patients who have had seizures in the past should be cautious about taking this drug.

• Tourette syndrome:

  • Patients with Tourette syndrome should use caution as stimulant drugs can unmask tics.

Phendimetrazine: Drug Interaction

Monitoring Parameters:

• Baseline cardiac evaluation for preexisting valvular heart disease and pulmonary hypertension is required.
• An echocardiogram should be done periodically during the treatment;
• Monitor weight and waist circumference;
• Monitor the blood pressure in patients especially those who have preexisting hypertension.

How to administer Phendimetrazine (Bontril)?

Extended-release:

• It is administered about 30 to 60 minutes before the first meal of the day. Avoid taking it in the evenings as it may cause insomnia and its efficacy may decline.

Immediate-release:

• It is administered about an hour before meals.

Mechanism of action of Phendimetrazine (Bontril):

• The sympathomimetic drug Phendimetrazine, which is also known as amphetamines, has similar properties to other stimulants like amphetamines. 
• It suppresses appetite and increases metabolism. It's believed to work by releasing dopamine and norepinephrine from the central nervous systems.

Metabolism

• • • It is metabolized into two metabolites (phenmetrazine and phendimetrazine-N-oxide).

Half-life elimination:

• It has a half-life elimination of about 3.7 hours

Excretion:

• It is excreted in urine.

International Brand Names of Phendimetrazine:

• Bontril PDM
• Anoran
• Antapentan
• Atrajine
• Fendy 35
• Furing
• Obesan-X
• Pendimen
• Phendirazine
• Plegine
• Prelu-2

Phendimetrazine Brand Names in Pakistan:

No Brands Available in Pakistan.