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==Contraindications and warnings==
==Contraindications and warnings==
*Patients with the following '''should not use''' Phentermine:
*Patients with the following '''should not use''' Phentermine:
**Have an allergy to any ingredient in Phentermine or other sympathomimetics (eg, pseudoephedrine)
**An [[allergy]] to any ingredient in Phentermine or other [[sympathomimetic]]s (eg, [[pseudoephedrine]])
**Are also taking dexfenfluramine, fenfluramine, furazolidone, guanadrel, guanethidine, or have taken a monoamine oxidase inhibitor (MAOI) (eg, phenelzine) in the last 14 days
**Are also taking [[dexfenfluramine]], [[fenfluramine]], [[furazolidone]], [[guanadrel]], [[guanethidine]], or have taken a [[monoamine oxidase inhibitor]] (MAOI) (eg, phenelzine) in the last 14 days
**Have moderate to severe high blood pressure, an overactive thyroid, glaucoma, heart or blood vessel disease, or severe narrowing of the blood vessels
**Have moderate to severe [[high blood pressure]], an [[overactive thyroid]], [[glaucoma]], heart or blood vessel disease, or severe narrowing of the blood vessels
**Are in an agitated state, or have a history of substance abuse
**Are in an agitated state, or have a history of [[substance abuse]]
*Some '''medical conditions may interact''' with Phentermine, patients with the following should consult with their doctor before using phentermine:
*Some '''medical conditions may interact''' with Phentermine, patients with the following should consult with their doctor before using phentermine:
**Are pregnant, planning to become pregnant, or are breast-feeding
**Are [[pregnant]], planning to become pregnant, or are [[breast-feeding]]
**Are taking any prescription or nonprescription medicine, herbal preparation, or dietary supplement
**Are taking any prescription or nonprescription medicine, herbal preparation, or dietary supplement
**Have [[allergies]] to medicines, foods, or other substances
**Have [[allergies]] to medicines, foods, or other substances
**Have a brain or spinal cord disorder, hardening of the arteries, high blood pressure, diabetes, or high cholesterol or lipid levels
**Have a brain or spinal cord disorder, hardening of the arteries, [[high blood pressure]], [[diabetes]], or [[high cholesterol]] or lipid levels
*Some '''medicines may interact''' with Phentermine, such as the following:
*Some '''medicines may interact''' with Phentermine, such as the following:
**Dexfenfluramine, fenfluramine, furazolidone, or MAOIs (eg, phenelzine) because the risk of serious side effects, such as increasing headache, high blood pressure, slow heart rate, elevated temperature, or possibly fatal lung problems, may be increased
**Dexfenfluramine, fenfluramine, furazolidone, or MAOIs (eg, phenelzine) because the risk of serious side effects, such as increasing headache, high blood pressure, slow heart rate, elevated temperature, or possibly fatal lung problems, may be increased
**Serotonin specific reuptake inhibitors (eg, fluoxetine) because the risk of their side effects may be increased by Phentermine
**Serotonin specific reuptake inhibitors (eg, fluoxetine) because the risk of their side effects may be increased by Phentermine
**Guanadrel or guanethidine because their effectiveness may be decreased by Phentermine
**Guanadrel or guanethidine because their effectiveness may be decreased by Phentermine


Phentermine should generally be avoided in patients with:
*Agitation
*[[Allergy]]/[[Hypersensitivity]] to other [[sympathomimetic amine]]s
*[[Atherosclerosis]]
*[[Cardiovascular disease]]
*[[Glaucoma]]
*[[High blood pressure]]
*[[Hyperthyroidism]]
*History of [[drug abuse]]

Additionally, this drug should not be used at the same time or within 14 days following the use of [[monoamine oxidase inhibitor]]s.


==History==
==History==

Revision as of 13:21, 2 June 2007

Phentermine
Clinical data
Pregnancy
category
  • C(United States); ? (Australia)
Routes of
administration		Oral
ATC code
Legal status
Legal status
  • C-IV (US)
Pharmacokinetic data
BioavailabilityPeak plasma levels occur within 1 to 4.5 hours. Absorption is usually complete by 4 to 6 hours
Protein bindingApproximately 96.3%
Metabolismhepatic
Elimination half-life16 to 31 hours
ExcretionUrinary elimination
Identifiers
  • 2-methyl-1-phenylpropan-2-amine and 2-methyl-amphetamine
CAS Number
PubChem CID
DrugBank
CompTox Dashboard (EPA)
ECHA InfoCard100.004.112 Edit this at Wikidata
Chemical and physical data
FormulaC10H15N
Molar mass149.233 g/mol g·mol−1

Phentermine is a drug primarily used as an appetite suppressant. Chemically, it is an amphetamine (and a phenethylamine). It is typically prescribed for individuals who are at increased medical risk because of their weight, as opposed to cosmetic weight loss. Phentermine is sold either as an immediate-release formulation (Adipex®) or as a slow-release resin (Ionamin®, Duromine® in Australia and New Zealand).

Commercial Trade Names

  • Adipex P
  • Pro-Fast SA
  • Anoxine-AM®
  • Fastin®
  • Ionamin®
  • Obephen®
  • Obermine®
  • Obestin-30®
  • Phentrol®

Indications

The patient insert states that Phentermine is used for reducing weight in obese patients when used short-term and combined with exercise, diet, and behavioral modification.

Phentermine is an appetite suppressant. It works by helping to release certain chemicals in the brain that control appetite.

Contraindications and warnings

  • Patients with the following should not use Phentermine:
  • Some medical conditions may interact with Phentermine, patients with the following should consult with their doctor before using phentermine:
  • Some medicines may interact with Phentermine, such as the following:
    • Dexfenfluramine, fenfluramine, furazolidone, or MAOIs (eg, phenelzine) because the risk of serious side effects, such as increasing headache, high blood pressure, slow heart rate, elevated temperature, or possibly fatal lung problems, may be increased
    • Serotonin specific reuptake inhibitors (eg, fluoxetine) because the risk of their side effects may be increased by Phentermine
    • Guanadrel or guanethidine because their effectiveness may be decreased by Phentermine

History

In 1959 phentermine first received approval from the FDA as an appetite suppressing drug. Phentermine hydrochloride then became available in the early 1970s. It was previously sold as Fastin® from King Pharmaceuticals for SmithKline Beecham, however in 1998 it was removed from the market. Medeva Pharmaceuticals sells the name brand of phentermine called Ionamin® and Gate Pharmaceuticals sells it as Adipex-P®. Phentermine is also currently sold as a generic. Since the drug was approved in 1959 there have been almost no clinical studies performed. The most recent study was in 1990 which combined phentermine with fenfluramine or dexfenfluramine and became known as Fen-Phen.

Although Fen-Phen was never approved by the FDA the agency did approve of the drug. A study was published in 1992 that Fen-Phen was more effective than diet and exercise with few side effects. However, in 1997 after 24 cases of heart valve disease in Fen-Phen users, fenfluramine and dexfenfluramine were voluntarily taken off the market at the request of the FDA. Studies later proved that nearly 30% of people taking fenfluramine or dexfenfluramine had abnormal valve findings. The FDA did not ask manufacturers to remove phentermine from the market.

Phentermine is still available by itself in most countries, including the U.S. However, because it is similar to amphetamines, individuals may develop an addiction to it. Hence, it is classified as a controlled substance in many countries. Internationally, phentermine is a schedule IV drug under the Convention on Psychotropic Substances.[1] In the United States, it is classified as a Schedule IV controlled substance under the Controlled Substances Act.

Mechanism of action

Phentermine, like many other prescription drugs, works with neurotransmitters in the brain. It is a centrally-acting stimulant and is a constitutional isomer (not to be confused with stereoisomer) of methamphetamine. It stimulates neuron bundles to release a particular group of neurotransmitters known as catecholamines; these include dopamine, epinephrine (also known as adrenalin), and norepinephrine (noradrenaline). The anorectic activity seen with these compounds would thus seem likely due to this effect on the central nervous system, which is consistent with current knowledge about central nervous system systems and feeding behavior. This is the same mechanism of action as other stimulant appetite suppressants such as diethylpropion and phendimetrazine. The neurotransmitters signal a fight-or-flight response in the body which, in turn, puts a halt to the hunger signal. As a result, it causes a loss in appetite because the brain does not receive the hunger message.

Clinical use

Generally, it is recommended by the Food and Drug Administration (FDA) that phentermine should be used short-term (usually interpreted as 'up to 12 weeks'), while following nonpharmacological approaches to weight loss such as healthy dieting and exercise. However, recommendations limiting its use for short-term treatment may be controversial. One reason given behind limiting its use to 12 weeks is drug tolerance, whereby phentermine loses its appetite-suppressing effects after the body adjusts to the drug. On the contrary, it has been shown that phentermine did not lose effectiveness in a 36-week trial.[2] Due to the risk of insomnia, it is generally recommended that the drug be taken either before breakfast or 1-2 hours after breakfast.

Side effects

Generally, phentermine appears to be relatively well tolerated.[3] It can produce side effects consistent with its catecholamine-releasing properties, e.g., tachycardia (increased heart rate) and elevated blood pressure, but the incidence and magnitude of these appear to be less than with the amphetamines. Because phentermine acts through sympathomimetic pathways, the drug may increase blood pressure and heart rate. It may also cause palpitations, restlessness, and insomnia. Additionally, individuals taking this drug on a long-term basis may develop euphoria and a psychological addiction to it.


More Common Symptoms

  • Insomnia
  • Increased blood pressure
  • Irritability
  • Nervousness
  • Sense of well-being

Less Common to Rare Symptoms

  • Blurred vision
  • Change in sexual desire
  • Clumsiness
  • Confusion
  • Diarrhea
  • Dizziness
  • Dry mouth
  • Headache
  • Irregular heartbeat
  • Nausea or vomiting
  • Psychosis
  • Skin rash or itching
  • Stomach pain
  • Tiredness
  • Unpleasant taste

Possible Overdose Symptoms

  • Confusion
  • Convulsions (seizures)
  • Dizziness
  • Fast Breathing
  • Fever
  • Hallucinations
  • Hostility with urge to attack
  • Irregular blood pressure
  • Irregular heartbeat
  • Lightheadedness or Fainting
  • Mental Depression, following a period of excitement
  • Tremors, Trembling, or Shaking
  • Overactive Reflexes
  • Panic
  • Restlessness
  • Severe nausea, vomiting or diarrhea
  • Stomach cramps
  • Tiredness or Weakness

In the News

On March 7, 2007, Detroit Pistons guard Lindsey Hunter was suspended 10 games without pay by the NBA after testing positive for phentermine.

Template:ChemicalSources

References and end notes

  1. ^ Incb.org (PDF file)
  2. ^ PMID 11054601
  3. ^ Nelson DL, Gehlert DR. (2006). "Central nervous system biogenic amine targets for control of appetite and energy expenditure" (HTML). Endocrine. 2006 Feb;29(1):49-60. PubMed. Retrieved 6 May. {{cite web}}: Check date values in: |accessdate= (help); Unknown parameter |accessyear= ignored (|access-date= suggested) (help)
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