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Phendimetrazine

Pronunciation

Pronunciation

(fen dye ME tra zeen)

Index Terms

  • Phendimetrazine Tartrate

Dosage Forms

Excipient information presented when available (limited, particularly for generics); consult specific product labeling. [DSC] = Discontinued product

Capsule Extended Release 24 Hour, Oral, as tartrate:

Generic: 105 mg

Tablet, Oral, as tartrate:

Bontril PDM: 35 mg [DSC] [scored; contains brilliant blue fcf (fd&c blue #1), fd&c yellow #10 (quinoline yellow), fd&c yellow #6 (sunset yellow)]

Generic: 35 mg

Brand Names: U.S.

  • Bontril PDM [DSC]

Pharmacologic Category

  • Anorexiant
  • Sympathomimetic

Pharmacology

Phendimetrazine is a sympathomimetic amine with pharmacologic properties similar to the amphetamines. The mechanism of action in reducing appetite appears to be secondary to CNS effects, including stimulation of the hypothalamus to release norepinephrine.

Metabolism

Forms 2 metabolites (phenmetrazine and phendimetrazine-N-oxide).

Excretion

Urine

Half-Life Elimination

~3.7 hours

Use: Labeled Indications

Obesity: Management of exogenous obesity as a short-term adjunct (a few weeks) in a regimen of weight reduction based on caloric restriction.

Contraindications

Hypersensitivity or idiosyncrasy to phendimetrazine, other sympathomimetic amines, or any component of the formulation; glaucoma; highly nervous or agitated patients; history of drug abuse; hyperthyroidism; coadministration with other anorectic agents or CNS stimulants; during or within 14 days following monoamine oxidase inhibitors therapy.

Additional contraindications:

Extended-release: History of cardiovascular disease (eg, arrhythmias, heart failure, coronary artery disease, uncontrolled hypertension, pulmonary hypertension, stroke); pregnancy; breast-feeding

Immediate-release: Advanced arteriosclerosis, symptomatic cardiovascular disease, moderate and severe hypertension

Dosing: Adult

Obesity (short-term): Oral:

Extended-release: 105 mg once daily 30 to 60 minutes before morning meal.

Immediate-release: 35 mg 2 or 3 times daily, 1 hour before meals. In some cases, one-half tablet (17.5 mg) per dose may be adequate (maximum: 70 mg 3 times daily).

Dosing: Geriatric

Refer to adult dosing.

Dosing: Pediatric

Obesity (short-term): Oral: Adolescents ≥17 years: Extended-release: Refer to adult dosing.

Dosing: Renal Impairment

There are no dosage adjustments provided in the manufacturer's labeling (has not been studied); use with caution (renally eliminated).

Dosing: Hepatic Impairment

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

Administration

Extended-release: Administer 30 to 60 minutes before morning meal.

Immediate-release: Administer 1 hour before meals.

Dietary Considerations

Most effective when combined with a low calorie diet and behavior modification counseling. Extended-release product should be taken 30 to 60 minutes before morning meal; immediate-release product should be taken 1 hour before meals.

Storage

Store at 15°C to 30°C (59°F to 86°F); protect capsules from moisture.

Drug Interactions

Acebrophylline: May enhance the stimulatory effect of CNS Stimulants. Avoid combination

Alcohol (Ethyl): May enhance the adverse/toxic effect of Phendimetrazine. Monitor therapy

Alkalinizing Agents: May decrease the excretion of Amphetamines. Consider therapy modification

Ammonium Chloride: May decrease the serum concentration of Amphetamines. This effect is likely due to an enhanced excretion of amphetamines in the urine. Monitor therapy

Analgesics (Opioid): Amphetamines may enhance the analgesic effect of Analgesics (Opioid). Monitor therapy

Antacids: May decrease the excretion of Amphetamines. Monitor therapy

Antihistamines: Amphetamines may diminish the sedative effect of Antihistamines. Monitor therapy

Antihypertensive Agents: Amphetamines may diminish the antihypertensive effect of Antihypertensive Agents. Monitor therapy

Antipsychotic Agents: May diminish the stimulatory effect of Amphetamines. Monitor therapy

Ascorbic Acid: May decrease the serum concentration of Amphetamines. Monitor therapy

AtoMOXetine: May enhance the hypertensive effect of Sympathomimetics. AtoMOXetine may enhance the tachycardic effect of Sympathomimetics. Monitor therapy

Cannabinoid-Containing Products: May enhance the tachycardic effect of Sympathomimetics. Exceptions: Cannabidiol. Monitor therapy

Carbonic Anhydrase Inhibitors: May decrease the excretion of Amphetamines. Exceptions: Brinzolamide; Dorzolamide. Monitor therapy

Doxofylline: Sympathomimetics may enhance the adverse/toxic effect of Doxofylline. Monitor therapy

Ethosuximide: Amphetamines may diminish the therapeutic effect of Ethosuximide. Amphetamines may decrease the serum concentration of Ethosuximide. Monitor therapy

Gastrointestinal Acidifying Agents: May decrease the serum concentration of Amphetamines. Monitor therapy

Iobenguane I 123: Sympathomimetics may diminish the therapeutic effect of Iobenguane I 123. Avoid combination

Ioflupane I 123: Amphetamines may diminish the diagnostic effect of Ioflupane I 123. Monitor therapy

Linezolid: May enhance the hypertensive effect of Sympathomimetics. Management: Reduce initial doses of sympathomimetic agents, and closely monitor for enhanced pressor response, in patients receiving linezolid. Specific dose adjustment recommendations are not presently available. Consider therapy modification

Lithium: May diminish the stimulatory effect of Amphetamines. Monitor therapy

MAO Inhibitors: May enhance the hypertensive effect of Amphetamines. While linezolid and tedizolid may interact via this mechanism, management recommendations differ from other monoamine oxidase inhibitors. Refer to monographs specific to those agents for details. Exceptions: Linezolid; Tedizolid. Avoid combination

Methenamine: May decrease the serum concentration of Amphetamines. This effect is likely due to an enhanced excretion of amphetamines in the urine. Monitor therapy

Multivitamins/Fluoride (with ADE): May decrease the serum concentration of Amphetamines. More specifically, the ascorbic acid (vitamin C) in many multivitamins may decrease amphetamine concentrations. Monitor therapy

Multivitamins/Minerals (with ADEK, Folate, Iron): May decrease the serum concentration of Amphetamines. Monitor therapy

Multivitamins/Minerals (with AE, No Iron): May decrease the serum concentration of Amphetamines. Specifically, vitamin C may impair absorption of amphetamines. Monitor therapy

PHENobarbital: Amphetamines may decrease the serum concentration of PHENobarbital. Monitor therapy

Phenytoin: Amphetamines may decrease the serum concentration of Phenytoin. Monitor therapy

Sympathomimetics: May enhance the adverse/toxic effect of other Sympathomimetics. Monitor therapy

Tedizolid: May enhance the hypertensive effect of Sympathomimetics. Tedizolid may enhance the tachycardic effect of Sympathomimetics. Monitor therapy

Tricyclic Antidepressants: May enhance the stimulatory effect of Amphetamines. Tricyclic Antidepressants may also potentiate the cardiovascular effects of Amphetamines. Monitor therapy

Urinary Acidifying Agents: May decrease the serum concentration of Amphetamines. Monitor therapy

Adverse Reactions

Frequency not defined.

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

<1% (Limited to important or life-threatening): Dilated cardiomyopathy, retinal vein occlusion (Cho 2016)

Warnings/Precautions

Concerns related to adverse effects:

• CNS depression: May cause CNS depression, which may impair physical or mental abilities; patients must be cautioned about performing tasks that require mental alertness (eg, operating machinery or driving).

• Pulmonary hypertension: May occur (rarely) and may be fatal. Use of an anorectic agent for >3 months increases the risk of pulmonary hypertension. If onset or aggravation of exertional dyspnea, or unexplained symptoms of angina pectoris, syncope, or lower extremity edema occur, immediately discontinue and evaluate for the possible presence of pulmonary hypertension.

• Valvular heart disease: The use of some anorectic agents has been associated with the development of valvular heart disease; contributing factors include use for extended periods of time, higher than recommended dose, and/or use in combination with other anorectic drugs. Not recommended in patients with known heart murmur or valvular heart disease.

Disease-related concerns:

• Diabetes: Use with caution in patients with diabetes mellitus; antidiabetic agent requirements may be altered with anorexic agents and concomitant dietary restrictions.

• Hypertension: Use with caution in patients with hypertension and other cardiovascular conditions that might be exacerbated by increases in blood pressure or heart rate.

• Renal impairment: Use with caution in patients with renal impairment.

• Seizure disorders: Use with caution in patients with a history of seizure disorders.

• Tourette syndrome: Use with caution in patients with Tourette syndrome; stimulants may unmask tics.

Concurrent drug therapy issues:

• Drug-drug interactions: Potentially significant interactions may exist, requiring dose or frequency adjustment, additional monitoring, and/or selection of alternative therapy. Consult drug interactions database for more detailed information.

Special populations:

• Elderly: Use caution in this age group due to the risk for causing dependence, hypertension, angina, and myocardial infarction.

Other warnings/precautions:

• Abuse potential: Phendimetrazine is pharmacologically related to the amphetamines, which have a high abuse potential; prolonged use may lead to dependency. Prescriptions should be written for the smallest quantity consistent with good patient care to minimize possibility of overdose.

• Appropriate use: Pharmacotherapy for obesity is indicated in patients with an initial body mass index (BMI) ≥30 kg/m2. Phendimetrazine is not recommended for patients who used any anorectic agents within the prior year.

• Discontinuation of therapy: Abrupt discontinuation following prolonged high doses may be associated with extreme fatigue and depression.

• Tolerance: Tolerance to the anorectic effect of phendimetrazine develops within a few weeks; discontinue use if tolerance develops; do not exceed recommended dosage in an attempt to overcome tolerance.

Monitoring Parameters

Baseline cardiac evaluation (for preexisting valvular heart disease, pulmonary hypertension); echocardiogram during therapy; weight, waist circumference; blood pressure

Pregnancy Risk Factor

X/C (product dependent)

Pregnancy Considerations

Animal reproduction studies have not been conducted. Use of specific products are contraindicated during pregnancy. The risks of using appetite-suppressing drugs in pregnant women are not known (NHLBI 1998). Weight loss therapy is generally not recommended for pregnant women. Obese and overweight women should be encouraged to participate in weight reduction programs prior to attempting pregnancy; weight gain during pregnancy should be determined by their prepregnancy BMI and current guidelines (ACOG 2013; ADA 2009).

Patient Education

• Discuss specific use of drug and side effects with patient as it relates to treatment. (HCAHPS: During this hospital stay, were you given any medicine that you had not taken before? Before giving you any new medicine, how often did hospital staff tell you what the medicine was for? How often did hospital staff describe possible side effects in a way you could understand?)

• Patient may experience dry mouth, insomnia, constipation, diarrhea, flushing, nausea, abdominal pain, or agitation. Have patient report immediately to prescriber mood changes, angina, tachycardia, severe dizziness, passing out, severe anxiety, severe headache, shortness of breath, swelling of arms or legs, blurred vision, decreased libido, arrhythmia, polyuria, difficult urination, tremors, or sweating a lot (HCAHPS).

• Educate patient about signs of a significant reaction (eg, wheezing; chest tightness; fever; itching; bad cough; blue skin color; seizures; or swelling of face, lips, tongue, or throat). Note: This is not a comprehensive list of all side effects. Patient should consult prescriber for additional questions.

Intended Use and Disclaimer: Should not be printed and given to patients. This information is intended to serve as a concise initial reference for health care professionals to use when discussing medications with a patient. You must ultimately rely on your own discretion, experience, and judgment in diagnosing, treating, and advising patients.

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