pharmacopeia
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/api/v1/drug/phentermine

Mechanism of action

Sourced from openFDA

Phentermine is a sympathomimetic amine with pharmacologic activity similar to the prototype drugs of this class used in obesity, amphetamine (d- and d / l-amphetamine). Drugs of this class used in obesity are commonly known as "anorectics" or "anorexigenics." It has not been established that the primary action of such drugs in treating obesity is one of appetite suppression since other central nervous system actions, or metabolic effects, may also be involved.

Dopamine UptakeMonoamine OxidaseNorepinephrine Uptake

Indications

Sourced from openFDA
  • Phentermine hydrochloride is indicated as a short-term (a few weeks) adjunct in a regimen of weight reduction based on exercise, behavioral modification and caloric restriction in the management of exogenous obesity for patients with an initial body mass index ≥ 30 kg/m 2 , or ≥ 27 kg/m 2 in the presence of other risk factors (e.g., controlled hypertension, diabetes, hyperlipidemia). Below is a chart of body mass index (BMI) based on various heights and weights.ICD-10: E66.9, E78.5, I10

Contraindications

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  • History of cardiovascular disease (e.g., coronary artery disease, stroke, arrhythmias, congestive heart failure, uncontrolled hypertension) During or within 14 days following the administration of monoamine oxidase inhibitors Hyperthyroidism Glaucoma Agitated states History of drug abuse Pregnancy [ see Use in Specific Populations (8.1) ] Nursing [ see Use in Specific Populations (8.3) ] Known hypersensitivity, or idiosyncrasy to the sympathomimetic amines History of cardiovascular disease (e.g., coronary artery disease, stroke, arrhythmias, congestive heart failure, uncontrolled hypertension) ( 4 ) During or within 14 days following the administration of monoamine oxidase inhibitors ( 4 ) Hyperthyroidism ( 4 ) Glaucoma ( 4 ) Agitated states ( 4 ) History of drug abuse ( 4 ) Pregnancy ( 4 , 8.1 ) Nursing ( 4 , 8.3 ) Known hypersensitivity, or idiosyncrasy to the sympathomimetic amines ( 4 )contraindicated

Dosage & administration

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Dosage should be individualized to obtain an adequate response with the lowest effective dose. (2.1) Late evening administration should be avoided (risk of insomnia). (2.1) Phentermine hydrochloride tablets can be taken with or without food. (2.1) Limit the dosage to 15 mg daily for patients with severe renal impairment (eGFR 15 to 29 mL/min/1.73 m 2 ) (2.2) 2.1 Exogenous Obesity Dosage should be individualized to obtain an adequate response with the lowest effective dose. The usual adult dose is one tablet (37.5 mg) daily, as prescribed by the physician, administered before breakfast or 1 to 2 hours after breakfast. The dosage may be adjusted to the patient’s need. For some patients, half tablet (18.75 mg) daily may be adequate, while in some cases it may be desirable to give half tablets (18.75 mg) two times a day. Phentermine hydrochloride is not recommended for use in pediatric patients ≤ 16 years of age. Late evening medication should be avoided because of the possibility of resulting insomnia. 2.2 Dosage in Patients With Renal Impairment The recommended maximum dosage of phentermine hydrochloride are 15 mg daily for patients with severe renal impairment (eGFR 15 to 29 mL min/1.73m 2 ). Avoid use of phentermine hydrochloride in patients with eGFR less than 15 mL/min/1.73m 2 or end-stage renal disease requiring dialysis [see Use in Specific Populations (8.6) and Clinical Pharmacology (12.3)].

Warnings & precautions

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Coadministration with other drugs for weight loss is not recommended (safety and efficacy of combination not established). ( 5.1 ) Rare cases of primary pulmonary hypertension have been reported. Phentermine should be discontinued in case of new, unexplained symptoms of dyspnea, angina pectoris, syncope or lower extremity edema. ( 5.2 ) Rare cases of serious regurgitant cardiac valvular disease have been reported. ( 5.3 ) Tolerance to the anorectic effect usually develops within a few weeks. If this occurs, phentermine should be discontinued. The recommended dose should not be exceeded. ( 5.4 ) Phentermine may impair the ability of the patient to engage in potentially hazardous activities such as operating machinery or driving a motor vehicle. ( 5.5 ) Risk of abuse and dependence. The least amount feasible should be prescribed or dispensed at one time in order to minimize the possibility of overdosage. ( 5.6 ) Concomitant alcohol use may result in an adverse drug reaction. ( 5.7 ) Use caution in patients with even mild hypertension (risk of increase in blood pressure). ( 5.8 ) A reduction in dose of insulin or oral hypoglycemic medication may be required in some patients. ( 5.9 ) 5.1 Coadministration With Other Drug Products for Weight Loss Phentermine hydrochloride tablets are indicated only as short-term (a few weeks) monotherapy for the management of exogenous obesity.

Adverse reactions

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The following adverse reactions are described, or described in greater detail, in other sections: Primary pulmonary hypertension [ see Warnings and Precautions (5.2) ] Valvular heart disease [ see Warnings and Precautions (5.3) ] Effect on the ability to engage in potentially hazardous tasks [ see Warnings and Precautions (5.5) ] Withdrawal effects following prolonged high dosage administration [ see Drug Abuse and Dependence (9.3) ] The following adverse reactions to phentermine have been identified: Cardiovascular Primary pulmonary hypertension and/or regurgitant cardiac valvular disease, palpitation, tachycardia, elevation of blood pressure, ischemic events. Central Nervous System Overstimulation, restlessness, dizziness, insomnia, euphoria, dysphoria, tremor, headache, psychosis. Gastrointestinal Dryness of the mouth, unpleasant taste, diarrhea, constipation, other gastrointestinal disturbances. Allergic Urticaria. Endocrine Impotence, changes in libido. Adverse events have been reported in the cardiovascular, central nervous, gastrointestinal, allergic, and endocrine systems. ( 6 ) To report SUSPECTED ADVERSE REACTIONS, contact Sun Pharmaceutical Industries, Inc. at 1-800-406-7984 or FDA at 1-800-FDA-1088 or www.fda.gov/medwatch.

Use in specific populations

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Nursing mothers: Discontinue drug or nursing taking into consideration importance of drug to mother. ( 4 , 8.3 ) Pediatric use: Safety and effectiveness not established. ( 8.4 ) Geriatric use: Due to substantial renal excretion, use with caution. ( 8.5 ) Renal Impairment: Avoid use in patients with eGFR less than 15 mL/min/1.73m 2 or end-stage renal disease requiring dialysis. (8.6) 8.1 Pregnancy Pregnancy Category X Phentermine is contraindicated during pregnancy because 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, due to obligatory weight gain that occurs in maternal tissues during pregnancy. Phentermine has pharmacologic activity similar to amphetamine (d- and d / l-amphetamine) [ see Clinical Pharmacology (12.1) ]. Animal reproduction studies have not been conducted with phentermine. If this drug is used during pregnancy, or if the patient becomes pregnant while taking this drug, the patient should be apprised of the potential hazard to a fetus. 8.3 Nursing Mothers It is not known if phentermine is excreted in human milk; however, other amphetamines are present in human milk.

Pharmacokinetics

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Metabolism
Following the administration of phentermine, phentermine reaches peak concentrations (C max ) after 3 to 4.4 hours. Specific Populations Renal Impairment Cumulative urinary excretion of phentermine under uncontrolled urinary pH conditions was 62% to 85%.

Overdosage

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The least amount feasible should be prescribed or dispensed at one time in order to minimize the possibility of overdosage. 10.1 Acute Overdosage Manifestations of acute overdosage include restlessness, tremor, hyperreflexia, rapid respiration, confusion, assaultiveness, hallucinations, and panic states. Fatigue and depression usually follow the central stimulation. Cardiovascular effects include tachycardia, arrhythmia, hypertension or hypotension, and circulatory collapse. Gastrointestinal symptoms include nausea, vomiting, diarrhea and abdominal cramps. Overdosage of pharmacologically similar compounds has resulted in fatal poisoning usually terminates in convulsions and coma. Management of acute phentermine hydrochloride intoxication is largely symptomatic and includes lavage and sedation with a barbiturate. Experience with hemodialysis or peritoneal dialysis is inadequate to permit recommendations in this regard. Acidification of the urine increases phentermine excretion. Intravenous phentolamine (Regitine ® , CIBA) has been suggested on pharmacologic grounds for possible acute, severe hypertension, if this complicates overdosage.

Approval history

Sourced from openFDA
  • Jul 1, 1976ANDAANDA083923Chartwell Rx
  • May 30, 1997ANDAANDA040190Elite Labs Inc
  • Jun 19, 1997ANDAANDA040228Elite Labs Inc
  • Jan 4, 2002ANDAANDA040377Prinston Inc
  • Oct 23, 2003ANDAANDA040526Sun Pharm Industries
  • Mar 21, 2008ANDAANDA040875Kvk Tech
  • Mar 31, 2008ANDAANDA040876Kvk Tech
  • Jul 17, 2012NDANDA022580Vivus Llc

FAERS reports

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Reference statistics only. FAERS reports are voluntarily submitted and are not incidence rates, safety signals, or causal evidence. Counts reflect reporting volume — how often a reaction was reported, not how often it occurs. For decision-grade use, consult openFDA and the FAERS Public Dashboard directly.
12,004 total reports matchedLatest report Share = reports listing the reaction ÷ total matched reports. Rows can sum to >100% because a single report often lists multiple reactions.
  1. 1Nausea7045.9%
  2. 2Headache6995.8%
  3. 3Drug Ineffective5744.8%
  4. 4Fatigue5644.7%
  5. 5Pain5204.3%
  6. 6Anxiety5074.2%
  7. 7Dizziness4904.1%
  8. 8Weight Increased4673.9%
  9. 9Insomnia4413.7%
  10. 10Paraesthesia4133.4%
  11. 11Constipation3693.1%
  12. 12Depression3512.9%
  13. 13Feeling Abnormal3302.7%
  14. 14Dry Mouth3292.7%
  15. 15Vomiting3122.6%

Literature

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Recent PubMed references pinned to Phentermine as a MeSH major topic. Citations link to pubmed.ncbi.nlm.nih.gov.

Clinical trials

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The 10 most recently updated of 81 ClinicalTrials.gov registrations naming Phentermine as an intervention. Registration is not evidence of efficacy or safety — reference crosswalk only.

Frequently asked questions

How does Phentermine work?
Phentermine is a sympathomimetic amine with pharmacologic activity similar to the prototype drugs of this class used in obesity, amphetamine (d- and d / l-amphetamine). Drugs of this class used in obesity are commonly known as "anorectics" or "anorexigenics." It has not been established that the primary action of such drugs in treating obesity is one of appetite suppression since other central nervous system actions, or metabolic effects, may also be involved.
What is Phentermine used for?
According to FDA labeling, Phentermine carries indications including: Phentermine hydrochloride is indicated as a short-term (a few weeks) adjunct in a regimen of weight reduction based on exercise, behavioral modification and caloric restriction in the management of exogenous obesity for patients with an initial body mass index ≥ 30 kg/m 2 , or ≥ 27 kg/m 2 in the presence of other risk factors (e.g., controlled hypertension, diabetes, hyperlipidemia). Below is a chart of body mass index (BMI) based on various heights and weights.. This is a reference summary of labeled uses, not medical advice or a treatment recommendation.
What class of drug is Phentermine?
Phentermine is classified as Centrally acting antiobesity products, Sympathomimetic Amine Anorectic, Dopamine Uptake Inhibitors, Monoamine Oxidase Inhibitors, Norepinephrine Uptake Inhibitors, Appetite Suppression, Increased Cerebral Cortex Dopamine Activity, Increased Cerebral Cortex Norepinephrine Activity, Increased Sympathetic Activity.
What are the brand names for Phentermine?
Phentermine is marketed under brand names including Adipex-P, Lomaira, Qsymia.
What are the contraindications for Phentermine?
Phentermine labeling lists contraindications including: History of cardiovascular disease (e.g., coronary artery disease, stroke, arrhythmias, congestive heart failure, uncontrolled hypertension) During or within 14 days following the administration of monoamine oxidase inhibitors Hyperthyroidism Glaucoma Agitated states History of drug abuse Pregnancy [ see Use in Specific Populations (8.1) ] Nursing [ see Use in Specific Populations (8.3) ] Known hypersensitivity, or idiosyncrasy to the sympathomimetic amines History of cardiovascular disease (e.g., coronary artery disease, stroke, arrhythmias, congestive heart failure, uncontrolled hypertension) ( 4 ) During or within 14 days following the administration of monoamine oxidase inhibitors ( 4 ) Hyperthyroidism ( 4 ) Glaucoma ( 4 ) Agitated states ( 4 ) History of drug abuse ( 4 ) Pregnancy ( 4 , 8.1 ) Nursing ( 4 , 8.3 ) Known hypersensitivity, or idiosyncrasy to the sympathomimetic amines ( 4 ). Always consult the full prescribing information and a clinician.
Note. Data for phentermine is illustrative MVP content compiled from public sources. pharmacopeia is for educational and informational use only and is not a substitute for professional medical advice.

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