Version July 2025
Weight management, short term (alternative agent):
Note: Avoid use due to side effects (eg, tachycardia, hypertension), potential for abuse, and availability of preferred weight-reducing drugs (Ref). Limit use to patients who cannot take preferred agents and who have a BMI ≥30 kg/m2 or patients with a BMI ≥27 kg/m2 and ≥1 weight-associated comorbidity (eg, dyslipidemia) and who do not have contraindications for use. Maximum duration: 12 weeks. Some patients may develop tolerance to appetite suppressive effects; phendimetrazine should be discontinued when this occurs.
Extended release: Oral: 105 mg once daily 30 to 60 minutes before morning meal.
Immediate release: Oral: 17.5 to 35 mg 2 or 3 times daily, 1 hour before meals (maximum: 70 mg 3 times daily).
Dosage adjustment for concomitant therapy: Significant drug interactions exist, requiring dose/frequency adjustment or avoidance. Consult drug interactions database for more information.
There are no dosage adjustments provided in the manufacturer's labeling (has not been studied); use with caution (renally eliminated).
There are no dosage adjustments provided in the manufacturer's labeling.
Refer to adult dosing.
Obesity (short-term): Oral: Adolescents ≥17 years: Extended-release: Refer to adult dosing.
There are no dosage adjustments provided in the manufacturer's labeling (has not been studied); use with caution (renally eliminated).
There are no dosage adjustments provided in the manufacturer's labeling.
The following adverse drug reactions and incidences are derived from product labeling unless otherwise specified.
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%, postmarketing, and/or case reports: Dilated cardiomyopathy, retinal vein occlusion (Cho 2016)
Hypersensitivity or idiosyncrasy to phendimetrazine, other sympathomimetic amines, or any component of the formulation; glaucoma; pregnancy (AACE/ACE [Garvey 2016]); 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.
Significant drug interactions exist, requiring dose/frequency adjustment or avoidance. Consult drug interactions database for more information.
Additional contraindications:
Extended release: History of cardiovascular disease (eg, arrhythmias, heart failure, coronary artery disease, uncontrolled hypertension, pulmonary hypertension, stroke); breastfeeding.
Immediate release: Advanced arteriosclerosis; symptomatic cardiovascular disease; moderate and severe hypertension.
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).
• Heart failure: In a scientific statement from the American Heart Association, phendimetrazine has been determined to be an agent that may cause direct myocardial toxicity (magnitude: major) (AHA [Page 2016]).
• 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.
Special populations:
• Bariatric surgery: Presurgical assessment of the indication for use, symptoms, and goals of therapy should be documented to enable postsurgical assessment. Monitor for continued efficacy and tolerability after bariatric surgery and consider switching to an alternative medication if symptoms worsen.
• Older adult: 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: Phendimetrazine is not approved for long-term use. Clinicians should carefully examine the potential benefits against potential risks associated with use of medications in this class. Therapy should be used in conjunction with a comprehensive weight management program. 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.
Excipient information presented when available (limited, particularly for generics); consult specific product labeling.
Capsule Extended Release 24 Hour, Oral, as tartrate:
Generic: 105 mg
Tablet, Oral, as tartrate:
Generic: 35 mg
Yes
Capsule ER 24 Hour Therapy Pack (Phendimetrazine Tartrate ER Oral)
105 mg (per each): $3.94
Tablets (Phendimetrazine Tartrate Oral)
35 mg (per each): $0.20 - $0.36
Disclaimer: A representative AWP (Average Wholesale Price) price or price range is provided as reference price only. A range is provided when more than one manufacturer's AWP price is available and uses the low and high price reported by the manufacturers to determine the range. The pricing data should be used for benchmarking purposes only, and as such should not be used alone to set or adjudicate any prices for reimbursement or purchasing functions or considered to be an exact price for a single product and/or manufacturer. Medi-Span expressly disclaims all warranties of any kind or nature, whether express or implied, and assumes no liability with respect to accuracy of price or price range data published in its solutions. In no event shall Medi-Span be liable for special, indirect, incidental, or consequential damages arising from use of price or price range data. Pricing data is updated monthly.
C-III
Extended release: Administer 30 to 60 minutes before morning meal.
Bariatric surgery: Phendimetrazine has an ER formulation. Bariatric surgery may significantly alter the release characteristics in an unknown manner. Providers should determine if the condition being treated can be safely monitored or if a switch to an alternative formulation is necessary (Ref). Phendimetrazine is also available as an IR formulation.
Immediate release: Administer 1 hour before meals.
Oral: Extended-release capsule: Administer 30 to 60 minutes before morning meal.
Weight management, short-term: Short-term (eg, ≤12 weeks) in a regimen of weight reduction based on exercise, behavioral modification, and caloric restriction in the management of exogenous obesity in patients with an initial BMI ≥30 kg/m2 or a BMI ≥27 kg/m2 with at least one weight-related comorbidity (eg, diabetes, hyperlipidemia) who have not responded to lifestyle modifications alone.
Bontril PDM may be confused with Bentyl
The Institute for Safe Medication Practices (ISMP) includes this medication among its list of drugs (contraindicated in pregnancy) which have a heightened risk of causing significant patient harm when used in error (High-Alert Medications in Community/Ambulatory Care Settings).
None known.
Note: Interacting drugs may not be individually listed below if they are part of a group interaction (eg, individual drugs within “CYP3A4 Inducers [Strong]” are NOT listed). For a complete list of drug interactions by individual drug name and detailed management recommendations, use the drug interactions program by clicking on the “Launch drug interactions program” link above.
Acebrophylline: May increase stimulatory effects of CNS Stimulants. Risk X: Avoid
Alkalinizing Agents: May decrease excretion of Amphetamines. Management: Consider alternatives to using amphetamines and alkalinizing agents in combination. If these agents must be used together, patients should be monitored closely for excessive amphetamine effects. Risk D: Consider Therapy Modification
Amifampridine: Agents With Seizure Threshold Lowering Potential may increase neuroexcitatory and/or seizure-potentiating effects of Amifampridine. Risk C: Monitor
Amisulpride (Oral): Agents With Seizure Threshold Lowering Potential may increase adverse/toxic effects of Amisulpride (Oral). Specifically, the risk of seizures may be increased. Risk C: Monitor
Ammonium Chloride: May decrease serum concentration of Amphetamines. This effect is likely due to an enhanced excretion of amphetamines in the urine. Risk C: Monitor
Antihypertensive Agents: Amphetamines may decrease antihypertensive effects of Antihypertensive Agents. Risk C: Monitor
Antipsychotic Agents: May decrease stimulatory effects of Amphetamines. Antipsychotic Agents may increase adverse/toxic effects of Amphetamines. Risk C: Monitor
ARIPiprazole Lauroxil: Agents With Seizure Threshold Lowering Potential may increase adverse/toxic effects of ARIPiprazole Lauroxil. Specifically, the risk of seizures may be increased. Risk C: Monitor
ARIPiprazole: Agents With Seizure Threshold Lowering Potential may increase adverse/toxic effects of ARIPiprazole. Specifically, the risk of seizures may be increased. Risk C: Monitor
Asenapine: Agents With Seizure Threshold Lowering Potential may increase adverse/toxic effects of Asenapine. Specifically, the risk of seizures may be increased. Risk C: Monitor
Atomoxetine: May increase hypertensive effects of Sympathomimetics. Atomoxetine may increase tachycardic effects of Sympathomimetics. Risk C: Monitor
Benperidol: Agents With Seizure Threshold Lowering Potential may increase adverse/toxic effects of Benperidol. Specifically, the risk of seizures may be increased. Risk C: Monitor
Blonanserin: Agents With Seizure Threshold Lowering Potential may increase adverse/toxic effects of Blonanserin. Specifically, the risk of seizures may be increased. Risk C: Monitor
Bornaprine: Sympathomimetics may increase anticholinergic effects of Bornaprine. Risk C: Monitor
Brexpiprazole: Agents With Seizure Threshold Lowering Potential may increase adverse/toxic effects of Brexpiprazole. Specifically, the risk of seizures may be increased. Risk C: Monitor
Bromperidol: Agents With Seizure Threshold Lowering Potential may increase adverse/toxic effects of Bromperidol. Specifically, the risk of seizures may be increased. Risk C: Monitor
BuPROPion: May increase neuroexcitatory and/or seizure-potentiating effects of Agents With Seizure Threshold Lowering Potential. Risk C: Monitor
Cannabinoid-Containing Products: May increase tachycardic effects of Sympathomimetics. Risk C: Monitor
Carbonic Anhydrase Inhibitors: May decrease excretion of Amphetamines. Risk C: Monitor
Cariprazine: Agents With Seizure Threshold Lowering Potential may increase adverse/toxic effects of Cariprazine. Specifically, the risk of seizures may be increased. Risk C: Monitor
ChlorproMAZINE: Agents With Seizure Threshold Lowering Potential may increase adverse/toxic effects of ChlorproMAZINE. Specifically, the risk of seizures may be increased. Risk C: Monitor
Clothiapine: Agents With Seizure Threshold Lowering Potential may increase adverse/toxic effects of Clothiapine. Specifically, the risk of seizures may be increased. Risk C: Monitor
CloZAPine: Agents With Seizure Threshold Lowering Potential may increase adverse/toxic effects of CloZAPine. Specifically, the risk of seizures may be increased. Risk C: Monitor
Cocaine (Topical): May increase hypertensive effects of Sympathomimetics. Management: Consider alternatives to use of this combination when possible. Monitor closely for substantially increased blood pressure or heart rate and for any evidence of myocardial ischemia with concurrent use. Risk D: Consider Therapy Modification
CYP2D6 Inhibitors (Moderate): May increase serum concentration of Amphetamines. Management: Monitor for amphetamine toxicities (including serotonin syndrome) if used with a moderate CYP2D6 inhibitor. Initiate amphetamine therapy at lower doses, monitor frequently, and adjust doses as needed. Discontinue amphetamines if serotoinin syndrome occurs Risk C: Monitor
CYP2D6 Inhibitors (Strong): May increase serum concentration of Amphetamines. Management: Monitor for amphetamine toxicities (including serotonin syndrome) if used with a strong CYP2D6 inhibitor. Initiate amphetamine therapy at lower doses, monitor frequently, and adjust doses as needed. Discontinue amphetamines if serotoinin syndrome occurs. Risk C: Monitor
Dihydralazine: Sympathomimetics may decrease therapeutic effects of Dihydralazine. Risk C: Monitor
Doxofylline: Sympathomimetics may increase adverse/toxic effects of Doxofylline. Risk C: Monitor
DroPERidol: Agents With Seizure Threshold Lowering Potential may increase adverse/toxic effects of DroPERidol. Specifically, the risk of seizures may be increased. Risk C: Monitor
Esketamine (Injection): May increase adverse/toxic effects of Sympathomimetics. Specifically, the risk for elevated heart rate, hypertension, and arrhythmias may be increased. Risk C: Monitor
Esketamine (Nasal): May increase hypertensive effects of CNS Stimulants. Risk C: Monitor
Fluorodopa F18: Coadministration of CNS Stimulants and Fluorodopa F18 may alter diagnostic results. Management: Discontinue medications used to treat Parkinson disease, including dopamine reuptake inhibitors and dopamine releasing agents, such as psychostimulants, 12 hours prior to fluorodopa F 18 administration if these medications can be safely withheld. Risk D: Consider Therapy Modification
Flupentixol: Agents With Seizure Threshold Lowering Potential may increase adverse/toxic effects of Flupentixol. Specifically, the risk of seizures may be increased. Risk C: Monitor
FluPHENAZine: Agents With Seizure Threshold Lowering Potential may increase adverse/toxic effects of FluPHENAZine. Specifically, the risk of seizures may be increased. Risk C: Monitor
Gastrointestinal Acidifying Agents: May decrease serum concentration of Amphetamines. Risk C: Monitor
Guanethidine: May increase hypertensive effects of Sympathomimetics. Guanethidine may increase arrhythmogenic effects of Sympathomimetics. Risk C: Monitor
Haloperidol: Agents With Seizure Threshold Lowering Potential may increase adverse/toxic effects of Haloperidol. Specifically, the risk of seizures may be increased. Risk C: Monitor
Iloperidone: Agents With Seizure Threshold Lowering Potential may increase adverse/toxic effects of Iloperidone. Specifically, the risk of seizures may be increased. Risk C: Monitor
Inhalational Anesthetics: Amphetamines may increase hypotensive effects of Inhalational Anesthetics. Risk C: Monitor
Inhibitors of the Proton Pump (PPIs and PCABs): May increase absorption of Amphetamines. Specifically, the amphetamine absorption rate may be increased in the first hours after dosing. Risk C: Monitor
Iobenguane Radiopharmaceutical Products: Amphetamines may decrease therapeutic effects of Iobenguane Radiopharmaceutical Products. Management: Discontinue all drugs that may inhibit or interfere with catecholamine transport or uptake for at least 5 biological half-lives before iobenguane administration. Do not administer these drugs until at least 7 days after each iobenguane dose. Risk X: Avoid
Iobenguane Radiopharmaceutical Products: CNS Stimulants may decrease therapeutic effects of Iobenguane Radiopharmaceutical Products. Management: Discontinue all drugs that may inhibit or interfere with catecholamine transport or uptake for at least 5 biological half-lives before iobenguane administration. Do not administer these drugs until at least 7 days after each iobenguane dose. Risk X: Avoid
Ioflupane I 123: Coadministration of Amphetamines and Ioflupane I 123 may alter diagnostic results. Risk C: Monitor
Iohexol: Agents With Seizure Threshold Lowering Potential may increase adverse/toxic effects of Iohexol. Specifically, the risk for seizures may be increased. Management: Discontinue agents that may lower the seizure threshold 48 hours prior to intrathecal use of iohexol. Wait at least 24 hours after the procedure to resume such agents. In nonelective procedures, consider use of prophylactic antiseizure drugs. Risk D: Consider Therapy Modification
Iomeprol: Agents With Seizure Threshold Lowering Potential may increase adverse/toxic effects of Iomeprol. Specifically, the risk for seizures may be increased. Management: Discontinue agents that may lower the seizure threshold 48 hours prior to intrathecal use of iomeprol. Wait at least 24 hours after the procedure to resume such agents. In nonelective procedures, consider use of prophylactic antiseizure drugs. Risk D: Consider Therapy Modification
Iopamidol: Agents With Seizure Threshold Lowering Potential may increase adverse/toxic effects of Iopamidol. Specifically, the risk for seizures may be increased. Management: Discontinue agents that may lower the seizure threshold 48 hours prior to intrathecal use of iopamidol. Wait at least 24 hours after the procedure to resume such agents. In nonelective procedures, consider use of prophylactic antiseizure drugs. Risk D: Consider Therapy Modification
Kratom: May increase adverse/toxic effects of Sympathomimetics. Risk X: Avoid
Landiolol: Sympathomimetics may decrease therapeutic effects of Landiolol. Risk C: Monitor
Levothyroxine: May increase therapeutic effects of Sympathomimetics. Sympathomimetics may increase therapeutic effects of Levothyroxine. Levothyroxine may increase adverse/toxic effects of Sympathomimetics. Specifically, the risk of coronary insufficiency may be increased in patients with coronary artery disease. Risk C: Monitor
Loxapine: Agents With Seizure Threshold Lowering Potential may increase adverse/toxic effects of Loxapine. Specifically, the risk of seizures may be increased. Risk C: Monitor
Lumateperone: Agents With Seizure Threshold Lowering Potential may increase adverse/toxic effects of Lumateperone. Specifically, the risk of seizures may be increased. Risk C: Monitor
Lurasidone: Agents With Seizure Threshold Lowering Potential may increase adverse/toxic effects of Lurasidone. Specifically, the risk of seizures may be increased. Risk C: Monitor
Methenamine: May decrease serum concentration of Amphetamines. This effect is likely due to an enhanced excretion of amphetamines in the urine. Risk C: Monitor
Methotrimeprazine: Agents With Seizure Threshold Lowering Potential may increase adverse/toxic effects of Methotrimeprazine. Specifically, the risk of seizures may be increased. Risk C: Monitor
Molindone: Agents With Seizure Threshold Lowering Potential may increase adverse/toxic effects of Molindone. Specifically, the risk of seizures may be increased. Risk C: Monitor
Monoamine Oxidase Inhibitors: May increase hypertensive effects 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. Risk X: Avoid
Multivitamins/Fluoride (with ADE): May decrease serum concentration of Amphetamines. More specifically, the ascorbic acid (vitamin C) in many multivitamins may decrease amphetamine concentrations. Risk C: Monitor
Multivitamins/Minerals (with ADEK, Folate, Iron): May decrease serum concentration of Amphetamines. Risk C: Monitor
Multivitamins/Minerals (with AE, No Iron): May decrease serum concentration of Amphetamines. Specifically, vitamin C may impair absorption of amphetamines. Risk C: Monitor
OLANZapine: Agents With Seizure Threshold Lowering Potential may increase adverse/toxic effects of OLANZapine. Specifically, the risk of seizures may be increased. Risk C: Monitor
Opioid Agonists: Amphetamines may increase analgesic effects of Opioid Agonists. Risk C: Monitor
Paliperidone: Agents With Seizure Threshold Lowering Potential may increase adverse/toxic effects of Paliperidone. Specifically, the risk of seizures may be increased. Risk C: Monitor
Periciazine: Agents With Seizure Threshold Lowering Potential may increase adverse/toxic effects of Periciazine. Specifically, the risk of seizures may be increased. Risk C: Monitor
Perphenazine: Agents With Seizure Threshold Lowering Potential may increase adverse/toxic effects of Perphenazine. Specifically, the risk of seizures may be increased. Risk C: Monitor
Pimozide: Agents With Seizure Threshold Lowering Potential may increase adverse/toxic effects of Pimozide. Specifically, the risk of seizures may be increased. Risk C: Monitor
Pipamperone: Agents With Seizure Threshold Lowering Potential may increase adverse/toxic effects of Pipamperone. Specifically, the risk of seizures may be increased. Risk X: Avoid
Polyethylene Glycol-Electrolyte Solution: Agents With Seizure Threshold Lowering Potential may increase adverse/toxic effects of Polyethylene Glycol-Electrolyte Solution. Specifically, the risk of seizure may be increased. Risk C: Monitor
Prochlorperazine: Agents With Seizure Threshold Lowering Potential may increase adverse/toxic effects of Prochlorperazine. Specifically, the risk of seizures may be increased. Risk C: Monitor
Promazine: Agents With Seizure Threshold Lowering Potential may increase adverse/toxic effects of Promazine. Specifically, the risk of seizures may be increased. Risk C: Monitor
QUEtiapine: Agents With Seizure Threshold Lowering Potential may increase adverse/toxic effects of QUEtiapine. Specifically, the risk of seizures may be increased. Risk C: Monitor
Quinolones: Amphetamines may increase cardiotoxic effects of Quinolones. Risk C: Monitor
RisperiDONE: Agents With Seizure Threshold Lowering Potential may increase adverse/toxic effects of RisperiDONE. Specifically, the risk of seizures may be increased. Risk C: Monitor
Selective Serotonin Reuptake Inhibitors (Strong CYP2D6 Inhibitors): Amphetamines may increase serotonergic effects of Selective Serotonin Reuptake Inhibitors (Strong CYP2D6 Inhibitors). This could result in serotonin syndrome. Selective Serotonin Reuptake Inhibitors (Strong CYP2D6 Inhibitors) may increase serum concentration of Amphetamines. Management: Monitor for amphetamine toxicities, including serotonin syndrome/serotonin toxicity (eg, hyperreflexia, clonus, hyperthermia, diaphoresis, tremor, autonomic instability). Initiate amphetamines at lower doses, monitor frequently, and adjust dose as needed. Risk C: Monitor
Serotonergic Agents (High Risk): Amphetamines may increase serotonergic effects of Serotonergic Agents (High Risk). This could result in serotonin syndrome. Management: Monitor for signs and symptoms of serotonin syndrome/serotonin toxicity (eg, hyperreflexia, clonus, hyperthermia, diaphoresis, tremor, autonomic instability). Initiate amphetamines at lower doses, monitor frequently, and adjust doses as needed. Risk C: Monitor
Sertindole: Agents With Seizure Threshold Lowering Potential may increase adverse/toxic effects of Sertindole. Specifically, the risk of seizures may be increased. Risk C: Monitor
Sodium Phosphates: Agents With Seizure Threshold Lowering Potential may increase adverse/toxic effects of Sodium Phosphates. Specifically, the risk of seizure or loss of consciousness may be increased in patients with significant sodium phosphate-induced fluid or electrolyte abnormalities. Risk C: Monitor
Solriamfetol: CNS Stimulants may increase hypertensive effects of Solriamfetol. CNS Stimulants may increase tachycardic effects of Solriamfetol. Risk C: Monitor
Solriamfetol: Sympathomimetics may increase hypertensive effects of Solriamfetol. Sympathomimetics may increase tachycardic effects of Solriamfetol. Risk C: Monitor
Sulpiride: Agents With Seizure Threshold Lowering Potential may increase adverse/toxic effects of Sulpiride. Specifically, the risk of seizures may be increased. Risk C: Monitor
Sympathomimetics: May increase adverse/toxic effects of Sympathomimetics. Risk C: Monitor
Tedizolid: May increase adverse/toxic effects of Sympathomimetics. Specifically, the risk for increased blood pressure and heart rate may be increased. Risk C: Monitor
Thioridazine: Agents With Seizure Threshold Lowering Potential may increase adverse/toxic effects of Thioridazine. Specifically, the risk of seizures may be increased. Risk C: Monitor
Thiothixene: Agents With Seizure Threshold Lowering Potential may increase adverse/toxic effects of Thiothixene. Specifically, the risk of seizures may be increased. Risk C: Monitor
Tricyclic Antidepressants: May increase adverse/toxic effects of Amphetamines. Tricyclic Antidepressants may potentiate the cardiovascular effects of Amphetamines. Amphetamines may increase serotonergic effects of Tricyclic Antidepressants. This could result in serotonin syndrome. Management: Monitor for signs and symptoms of serotonin syndrome/serotonin toxicity (eg, hyperreflexia, clonus, hyperthermia, diaphoresis, tremor, autonomic instability, mental status changes) and increased cardiovascular effects when these agents are combined. Risk C: Monitor
Trifluoperazine: Agents With Seizure Threshold Lowering Potential may increase adverse/toxic effects of Trifluoperazine. Specifically, the risk of seizures may be increased. Risk C: Monitor
Urinary Acidifying Agents: May decrease serum concentration of Amphetamines. Risk C: Monitor
Ziprasidone: Agents With Seizure Threshold Lowering Potential may increase adverse/toxic effects of Ziprasidone. Specifically, the risk of seizures may be increased. Risk C: Monitor
Zuclopenthixol: Agents With Seizure Threshold Lowering Potential may increase adverse/toxic effects of Zuclopenthixol. Specifically, the risk of seizures may be increased. Risk C: Monitor
Obesity increases the risk of infertility. Optimal weight control prior to conception improves pregnancy outcomes. However, medications for weight loss are not recommended prior to pregnancy due to safety issues and adverse events. Weight loss medications should be discontinued prior to conception (ACOG 2021; Wharton 2020).
An increased risk of adverse maternal and fetal events is associated with obesity. However, moderate gestational weight gain based on prepregnancy BMI is required for positive fetal outcomes in all pregnancies, including patients with overweight or obesity. Therefore, medications for weight loss therapy are not recommended during pregnancy (ACOG 2021; Wharton 2020).
Use is contraindicated by some manufacturers in pregnant patients (lack of potential benefit and possible fetal harm).
It is unknown if phendimetrazine is present in breast milk; however, other amphetamines have been detected in breast milk.
Use is contraindicated by some manufacturers in breastfeeding patients. Due to safety concerns, medications for weight loss therapy are not recommended for patients who are breastfeeding (Wharton 2020).
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.
Baseline cardiac evaluation (for preexisting valvular heart disease, pulmonary hypertension); weight; waist circumference; BP; heart rate.
Adult classification of weight by BMI (kg/m2) (NHLBI 1998):
Underweight: <18.5
Normal: 18.5 to 24.9
Overweight: 25 to 29.9
Obesity, class I: 30 to 34.9
Obesity, class II: 35 to 39.9
Obesity, class III: ≥40
Waist circumference: In adults with a BMI of 25 to 34.9 kg/m2, high-risk waist circumference is defined as (NHLBI 1998):
Males >102 cm (>40 in)
Females >88 cm (>35 in)
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).
Half-life elimination: ~3.7 hours
Excretion: Urine
