Children ≥12 years of age: 35 mg 2 or 3 times daily, given 1 hour before meals. A dosage of 17.5 mg 2 or 3 times daily may be adequate for some patients.
Extended-release Capsules
Oral
Children ≥12 years of age: 105 mg once daily, given 30–60 minutes before the morning meal.
Adults
Exogenous Obesity
Conventional Tablets
Oral
35 mg 2 or 3 times daily, given 1 hour before meals. A dosage of 17.5 mg 2 or 3 times daily may be adequate for some patients.
Extended-release Capsules
Oral
105 mg once daily, given 30–60 minutes before the morning meal.
Prescribing Limits
Pediatric Patients
Exogenous Obesity
Oral
Children ≥12 years of age: Maximum 70 mg 3 times daily (as conventional tablets).
Children ≥12 years of age: Maximum 105 mg once daily (as extended-release capsules).
Adults
Exogenous Obesity
Oral
Maximum 70 mg 3 times daily (as conventional tablets).
Maximum 105 mg once daily (as extended-release capsules).
Highly nervous or agitated state or history of drug abuse.
Concurrent therapy with other CNS stimulants or anorexigenic drugs.
Within 14 days of MAO inhibitor therapy.
Known hypersensitivity or idiosyncrasy to sympathomimetic amines.
Warnings/Precautions
Warnings
Primary Pulmonary Hypertension
Risk of primary pulmonary hypertension (frequently fatal), particularly when used in combination with at least one other anorexigenic agent, or in those with a history of receiving at least one other anorexigenic agent. Risk increased by 23-fold when anorexigenic agents are used for >3 months. Increased risk following repeated courses of phendimetrazine cannot be ruled out.
Discontinue immediately if new-onset or exacerbation of exertional dyspnea or unexplained symptoms of angina, syncope, or edema of the lower extremities occur, and evaluate for possible pulmonary hypertension.
Valvular Heart Disease
Valvular heart disease reported following use of some anorexigenic agents (e.g., fenfluramine, dexfenfluramine [both no longer commercially available in the US]), particularly when used for extended periods of time, at higher than recommended dosages, and/or in combination with other anorexigenic agents.
Abnormal heart valve findings have been reported in some patients receiving phendimetrazine. Weigh potential risks against benefits of therapy.
Consider performing baseline cardiac evaluation to detect preexisting valvular heart diseases prior to initiation of therapy. Use not recommended in patients with known heart murmur or valvular heart disease. Echocardiogram during and after treatment may be useful for detecting any valvular disorders that may occur.
To limit unwarranted exposure and risks, continue therapy only if patient has achieved satisfactory weight loss (e.g., ≥4 pounds [1.8 kg], or as determined by physician and patient) within first 4 weeks of therapy.
Tolerance to Anorexigenic Effect
Tolerance to anorexigenic effect usually develops within a few weeks. When it does, discontinue therapy; do not attempt to increase effect by exceeding recommended dosage.
CNS Effects
Performance of activities requiring mental alertness or physical coordination may be impaired. (See Advice to Patients.)
Abuse Potential
Potential for abuse; habituation or addiction reported with phendimetrazine and similar drugs (e.g., amphetamines).
Manifestations of chronic intoxication may include psychosis resembling schizophrenia, severe dermatoses, marked insomnia, irritability, hyperactivity, and personality changes.
Abrupt discontinuance following prolonged high dosage may result in extreme fatigue, depression, and sleep EEG changes.
Sensitivity Reactions
Tartrazine Sensitivity
Some preparations (e.g., 35-mg conventional tablets manufactured by Sandoz) contain tartrazine (FD&C yellow No. 5), which may cause allergic reactions including bronchial asthma in susceptible individuals. Incidence of tartrazine sensitivity is low, but it frequently occurs in patients who are sensitive to aspirin.
General Precautions
Prescribe and dispense in the smallest feasible quantity to minimize possibility of overdosage.
Hypertension
Use with caution in patients with mild hypertension; monitor BP closely. Contraindicated in those with moderate or severe hypertension.
Diabetes Mellitus
Use with caution in patients with diabetes mellitus; insulin requirements may decrease in association with phendimetrazine use and the concomitant dietary regimen and weight loss.
Specific Populations
Pregnancy
Category C.
Whether potential benefits of anorexigenic agents outweigh risks is questionable; use of these agents during pregnancy (especially during the first trimester) probably should be considered a contraindication.
Lactation
Not known whether phendimetrazine is distributed into milk; however, because of its low molecular weight, the drug is expected to distribute into milk. Caution if used in nursing women.
Avoid concomitant use (including with OTC drugs or herbal preparations) (see Contraindications under Cautions); phendimetrazine not recommended for patients who used any anorexigenic agents within prior year
Possible decrease in insulin requirements in patients with diabetes mellitus
Use concomitantly with caution
MAO inhibitors
Potential for hypertensive crisis
Phendimetrazine use during or within 14 days of MAO inhibitor use is contraindicated
Pharmacokinetics
Absorption
Bioavailability
Readily absorbed from the GI tract following oral administration.
Duration
Effects persist for about 4 hours.
Extended-release capsules produce prolonged therapeutic effect. Effects achieved with one 105-mg extended-release capsule are similar to those achieved with three 35-mg conventional tablets administered at 4-hour intervals.
Distribution
Extent
Not known whether phendimetrazine is distributed into milk; however, because of its low molecular weight, the drug is expected to distribute into milk.
Elimination
Metabolism
Undergoes limited biotransformation.
Elimination Route
Excreted principally in urine.
Half-life
Conventional tablets: Approximately 1.9–3.7 hours.
Extended-release capsules: Approximately 3.7–9.8 hours.
Stability
Storage
Oral
Conventional Tablets and Extended-release Capsules
Tight, light-resistant containers at 20–25°C. Protect from moisture.
Actions
Produces anorexigenic effect and loss of weight.
Like other amphetamine derivatives, has no primary effect on appetite; anorexigenic action probably is secondary to CNS stimulation.
Advice to Patients
Potential for drug to impair mental alertness or physical coordination; caution when driving or operating machinery until effects on individual are known.
Importance of informing clinicians of existing or contemplated concomitant therapy, including prescription and OTC drugs, as well as any concomitant illnesses (e.g., glaucoma, high BP, cardiac disease).
Importance of women informing clinicians if they are or plan to become pregnant or plan to breast-feed.
Importance of informing patients of other important precautionary information. (See Cautions.)
Preparations
Excipients in commercially available drug preparations may have clinically important effects in some individuals; consult specific product labeling for details.
Subject to control under the Federal Controlled Substances Act of 1970 as a schedule III (C-III) drug.
Remember, keep this and all other medicines out of the reach of children,
never share your medicines with others, and use this medication only for the indication prescribed.
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