Description

Simple

A medication used temporarily to promote weight loss along with other methods, such as exercise and diet changes.

Clinical

A sympathomimetic anorectic agent used as a short-term adjunct therapy that is included in a regimen of weight reduction in cases of exogenous obesity.

Overview

Phentermine is a sympathomimetic amine anorectic agent and it was introduced in 1959 as part of an anti-obesity combination drug.[1, 2] It is chemically related to amphetamine and it is commonly referred to as an atypical amphetamine.[4] Phentermine has not been reported an addictive potential which allows this agent to be classified under the Schedule IV drugs (low abuse potential).[3]

Phentermine was FDA approved for short-term weight management in 1959 and it became widely used in 1960. This initial product, formed by the combination of phentermine with [fenf... Read more

Pharmacology

Indication

Phentermine is indicated, alone or in combination with topiramate, as a short-term adjunct, not pass a few weeks, in a regimen of weight reduction based on exercise, behavioral modifications and caloric restriction in the management of exogenous obesity for patients with an initial body mass index (... Read more

Pharmacodynamic

It is reported that the main mechanism of action of phentermine is the generation of appetite suppression, maybe due to the increase in leptin, but it is considered that other mechanisms should be involved.[ Read more

Mechanism of action

Phentermine is an indirect-acting sympathomimetic agent that acts by releasing noradrenaline from the presynaptic vesicles in the lateral hypothalamus. This increase in noradrenaline concentration in the synaptic cleft results in the stimulation of beta2-adrenergic receptors.[ Read more

Absorption

Phentermine shows a dose-dependent pharmacokinetic profile. After oral administration of a dose of 15 mg, the maximal concentration was achieved after 6 hours and its bioavailability was not affected by the consumption of high-fat meals.[ Read more

Protein binding

The protein binding of phentermine is determined to be of 17.5%.[ Read more

Volume of distribution

The reported volume of distribution for phentermine is reported to be of 5 L/kg.[11]

Clearance

The reported clearance when administered orally is 8.79 L/h as observed in pharmacokinetic population studies.[13]

Half life

The mean terminal half-life of phentermine is reported to be of approximately 20 hours.[ Read more

Route of elimination

Phentermine is excreted mainly in the urine from which about 70-80% of the administered dose can be found as the unchanged drug.[ Read more

Toxicity

The reported LD50 after oral administration of phentermine in rats is reported to be of 151 mg/kg.[12] Reports of acute overdose include restlessness, tremors, hyperreflexia, rapid respiration, confusion, assaultiveness, halluc... Read more

Adverse Effects

Contraindications

  • Hypersensitivity:
    • true
  • Regions: US
  • Route:
    • Oral
  • Dose Form:
    • Capsule
    • Tablet
    • Tablet, orally disintegrating
  • Regions: US
  • Patient Conditions:
      • Name: Nursing
      • Drugbank Id: DBCOND0040121
  • Route:
    • Oral
  • Dose Form:
    • Capsule
    • Tablet
    • Tablet, orally disintegrating
  • Regions: US
  • Patient Conditions:
      • Name: Pregnancy
      • Drugbank Id: DBCOND0018394
  • Route:
    • Oral
  • Dose Form:
    • Capsule
    • Tablet
    • Tablet, orally disintegrating
  • Regions: US
  • Patient Conditions:
      • Name: History of drug abuse
      • Drugbank Id: DBCOND0107489
  • Route:
    • Oral
  • Dose Form:
    • Capsule
    • Tablet
    • Tablet, orally disintegrating
  • Regions: US
  • Patient Conditions:
      • Name: Agitated state
      • Drugbank Id: DBCOND0107488
  • Route:
    • Oral
  • Dose Form:
    • Capsule
    • Tablet
    • Tablet, orally disintegrating
  • Regions: US
  • Patient Conditions:
      • Name: Glaucoma
      • Drugbank Id: DBCOND0010013
  • Route:
    • Oral
  • Dose Form:
    • Capsule
    • Tablet
    • Tablet, orally disintegrating
  • Regions: US
  • Patient Conditions:
      • Name: Hyperthyroidism
      • Drugbank Id: DBCOND0009048
  • Route:
    • Oral
  • Dose Form:
    • Capsule
    • Tablet
    • Tablet, orally disintegrating
  • Regions: US
  • Patient Conditions:
      • Name: Concomitant use or 14 days after discontinuation
      • Drugbank Id: DBCOND0117358
  • With Categories:
      • Name: Monoamine Oxidase Inhibitors
      • Drugbank Id: DBCAT001004
      • Mesh Id: D008996
  • Route:
    • Oral
  • Dose Form:
    • Capsule
    • Tablet
    • Tablet, orally disintegrating
  • Regions: US
  • Patient Conditions:
      • Name: History of cardiovascular disease
      • Drugbank Id: DBCOND0102767

Food Interactions

  • Limit caffeine intake.
  • Take without regard to meals.

Interactions

Type in a drug name to check for interaction with Phentermine
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  • Paracetamol(acetaminophen)
  • Paxil(paroxetine)
  • Pamelor(nortriptyline)
  • Panadol(acetaminophen)
  • Patanol(olopatadine ophthalmic)
  • Pataday(olopatadine ophthalmic)
  • Parnate(tranylcypromine)
  • Pazeo(olopatadine ophthalmic)
1-(3-Mercapto-2-Methyl-Propionyl)-Pyrrolidine-2-Carboxylic Acid
The risk or severity of hypertension can be increased when Phentermine is combined with 1-(3-Mercapto-2-Methyl-Propionyl)-Pyrrolidine-2-Carboxylic Acid.
1-benzylimidazole
The therapeutic efficacy of 1-benzylimidazole can be decreased when used in combination with Phentermine.
2,4-thiazolidinedione
The therapeutic efficacy of 2,4-thiazolidinedione can be increased when used in combination with Phentermine.
2,5-Dimethoxy-4-ethylamphetamine
The risk or severity of serotonin syndrome can be increased when Phentermine is combined with 2,5-Dimethoxy-4-ethylamphetamine.
2,5-Dimethoxy-4-ethylthioamphetamine
The risk or severity of serotonin syndrome can be increased when Phentermine is combined with 2,5-Dimethoxy-4-ethylthioamphetamine.
3-isobutyl-1-methyl-7H-xanthine
The risk or severity of adverse effects can be increased when Phentermine is combined with 3-isobutyl-1-methyl-7H-xanthine.
3,5-diiodothyropropionic acid
The risk or severity of adverse effects can be increased when Phentermine is combined with 3,5-diiodothyropropionic acid.
3,5-Diiodotyrosine
The risk or severity of adverse effects can be increased when Phentermine is combined with 3,5-Diiodotyrosine.
4-Bromo-2,5-dimethoxyamphetamine
The risk or severity of serotonin syndrome can be increased when Phentermine is combined with 4-Bromo-2,5-dimethoxyamphetamine.
4-hydroxycoumarin
The metabolism of 4-hydroxycoumarin can be decreased when combined with Phentermine.
4-Methoxyamphetamine
The risk or severity of hypertension can be increased when Phentermine is combined with 4-Methoxyamphetamine.
5-methoxy-N,N-dimethyltryptamine
The risk or severity of serotonin syndrome can be increased when Phentermine is combined with 5-methoxy-N,N-dimethyltryptamine.
6-Deoxyerythronolide B
The metabolism of Phentermine can be decreased when combined with 6-Deoxyerythronolide B.
6-O-benzylguanine
The risk or severity of adverse effects can be increased when Phentermine is combined with 6-O-benzylguanine.
7-Deazaguanine
The risk or severity of adverse effects can be increased when Phentermine is combined with 7-Deazaguanine.
7-ethyl-10-hydroxycamptothecin
The metabolism of Phentermine can be decreased when combined with 7-ethyl-10-hydroxycamptothecin.
7,8-Dichloro-1,2,3,4-tetrahydroisoquinoline
7,8-Dichloro-1,2,3,4-tetrahydroisoquinoline may increase the hypertensive activities of Phentermine.
7,9-Dimethylguanine
The risk or severity of adverse effects can be increased when Phentermine is combined with 7,9-Dimethylguanine.
8-azaguanine
The risk or severity of adverse effects can be increased when Phentermine is combined with 8-azaguanine.
8-chlorotheophylline
The risk or severity of adverse effects can be increased when Phentermine is combined with 8-chlorotheophylline.
13 References
  1. 1 . Johnson DB, Quick J: Topiramate And Phentermine .PubMed: 29489234
  2. 2 . Ryder JR, Kaizer A, Rudser KD, Gross A, Kelly AS, Fox CK: Effect of phentermine on weight reduction in a pediatric weight management clinic. Int J Obes (Lond). 2017 Jan;41(1):90-93. doi: 10.1038/ijo.2016.185. Epub 2016 Oct 24.PubMed: 27773937
  3. 3 . Kiortsis DN: A review of the metabolic effects of controlled-release Phentermine/Topiramate. Hormones (Athens). 2013 Oct-Dec;12(4):507-16.PubMed: 24457398
  4. 4 . Garvey WT: Phentermine and topiramate extended-release: a new treatment for obesity and its role in a complications-centric approach to obesity medical management. Expert Opin Drug Saf. 2013 Sep;12(5):741-56. doi: 10.1517/14740338.2013.806481. Epub 2013 Jun 6.PubMed: 23738843
  5. 5 . Bersoux S, Byun TH, Chaliki SS, Poole KG: Pharmacotherapy for obesity: What you need to know. Cleve Clin J Med. 2017 Dec;84(12):951-958. doi: 10.3949/ccjm.84a.16094.PubMed: 29244650
  6. 6 . Weigle DS: Pharmacological therapy of obesity: past, present, and future. J Clin Endocrinol Metab. 2003 Jun;88(6):2462-9. doi: 10.1210/jc.2003-030151.PubMed: 12788841
  7. 7 . Adebonojo FO: Primary exogenous obesity. A conceptual classification. Clin Pediatr (Phila). 1974 Sep;13(9):715-8. doi: 10.1177/000992287401300901.PubMed: 4415200
  8. 8 . May S. (2009). Weight-Loss Drugs. Chelsea House Publishers.
  9. 9 . Barceloux D.G. (2012). Medical toxicology of drug abuse: Synthesized chemicals and psychoactive plants.. Wiley.
  10. 10 . EmpowerPharmacy Link
  11. 11 . Inchem Link
  12. 12 . FDA reports Link
  13. 13 . QSYMIA (phentermine/topiramate) FDA label File