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Information about Phentermine

Phentermine is an appetite suppressant of the amphetamine and phenethylamine class.

It is approved as an appetite suppressant to help reduce weight in obese patients when used short-term and combined with exercise, diet, and behavioral modification. It is typically prescribed for individuals who are at increased medical risk because of their weight and works by helping to release certain chemicals in the brain that control appetite.

Commercial trade names

  • Adipex P (Immediate release)
  • Anoxine-AM®
  • Fastin®
  • Ionamin® (Slow Release Resin, Australia)
  • Duromine® (Slow Release Resin, New Zealand)
  • Obephen®
  • Obermine®
  • Obestin-30®
  • Phentrol®
  • Pro-Fast SA
  • '''Redusa
  • '''Panbesy
  • Phentermine Trenker
  • '''Obenix
  • '''Oby-Trim

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.

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.

Dosing and administration

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.

Contraindications and warnings

  • Patients with the following should not use Phentermine:
  • An allergy to any ingredient in Phentermine or other sympathomimetics (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
  • 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
  • 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 taking any prescription or nonprescription medicine, herbal preparation, or dietary supplement
  • 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
  • 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

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, phentermine has the potential to cause physical and psychological dependence.

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.

References

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 on 6 May, 2006.

External links

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EugeroicsAdrafinil • Carphedon • Modafinil/Armodafinil
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See also
 •  • [ e]
Antiobesity preparations (A08)
Centrally actingPhentermine - Fenfluramine - Amfepramone - Dexfenfluramine - Mazindol - Cathine - Clobenzorex - Sibutramine - Rimonabant
Peripherally actingOrlistat
Anorectics, anorexigenics or appetite suppressants are drugs that reduce the appetite ("anorectic", from the Greek an- = "not" and oreg- = "extend, reach").
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Amphetamine or Amfetamine(Alpha-Methyl-PHenEThylAMINE), also known as beta-phenyl-isopropylamine and benzedrine, is a prescription stimulant commonly used to treat Attention-deficit hyperactivity disorder (ADHD) in adults and children.
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Phenethylamine, or β-Phenylethylamine, is an alkaloid and monoamine. In the human brain, it is believed to function as a neuromodulator or neurotransmitter (trace amine).
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GlaxoSmithKline

Public (LSE:  GSK
NYSE:  GSK )
Founded 2000, by merger of Glaxo Wellcome and SmithKline Beecham
Headquarters London, England, UK

Key people Sir Chris Gent, Chairman
Dr Jean-Pierre Garnier, Chief Executive
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Fenfluramine is a drug that was part of the Fen-Phen anti-obesity medication (the other drug being phentermine). Also known as Pondimin, fenfluramine was introduced on the U.S. market in 1973.
..... Click the link for more information.
Dexfenfluramine, also marketed under the name Redux, is a serotoninergic anorectic drug. It was for some years in the mid-1990s approved by the United States Food and Drug Administration for the purposes of weight loss.
..... Click the link for more information.
Fen-phen was an anti-obesity medication (an anorectic) which consisted of two drugs: fenfluramine and phentermine. Fenfluramine, and later, a related drug, dexfenfluramine, was marketed by American Home Products, now known as Wyeth.
..... Click the link for more information.
Amphetamine or Amfetamine(Alpha-Methyl-PHenEThylAMINE), also known as beta-phenyl-isopropylamine and benzedrine, is a prescription stimulant commonly used to treat Attention-deficit hyperactivity disorder (ADHD) in adults and children.
..... Click the link for more information.
Drug addiction is a condition characterized by compulsive drug intake, craving and seeking, despite what the majority of society may perceive as the negative consequences associated with drug use.
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A controlled substance is generally a drug or chemical whose manufacture, possession and use are regulated by a government. This may include Illegal drugs and Prescription medications (designated Controlled Drug in the United Kingdom).
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The Convention on Psychotropic Substances is a United Nations treaty designed to control psychoactive drugs such as amphetamines, barbiturates, and psychedelics. During the 1960s, drug use increased greatly around the world, especially in Western nations.
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Schedule IV or Schedule 4 is a legal category assigned to substances in certain jurisdictions:
  • In Australia: Schedule 4
  • In Canada: Schedule IV (Canada)
  • In Estonia: Narcotic Drugs and Psychotropic Substances Act (Estonia)

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The Controlled Substances Act (CSA) was enacted into law by the Congress of the United States as Title II of the Comprehensive Drug Abuse Prevention and Control Act of 1970.
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Neurotransmitters are chemicals that are used to relay, amplify and modulate signals between a neuron and another cell. According to the prevailing beliefs of the 1960s, a chemical can be classified as a neurotransmitter if it meets the following conditions:

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Stimulants are drugs that temporarily increase alertness and awareness. They usually have increased side-effects with increased effectiveness, and the more powerful variants are therefore often prescription medicines or illegal drugs.
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Structural isomerism (or constitutional isomerism) is a form of isomerism in which molecules with the same molecular formula have atoms bonded together in different orders, as opposed to stereoisomerism.
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Stereoisomers are isomeric molecules whose atomic connectivity is the same but whose atomic arrangement in space is different.

Enantiomers

Main article: enantiomer

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Methamphetamine (methylamphetamine or desoxyephedrine), popularly shortened to meth and also nicknamed "ice", is a psychostimulant and sympathomimetic drug.
..... Click the link for more information.
Neurons (also known as neurones and nerve cells) are electrically excitable cells in the nervous system that process and transmit information. In vertebrate animals, neurons are the core components of the brain, spinal cord and peripheral nerves.
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Catecholamines are chemical compounds derived from the amino acid tyrosine containing catechol and amine groups. Some of them are biogenic amines. Catecholamines are water soluble and are 50% bound to plasma proteins, so they circulate in the bloodstream.
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Dopamine is a hormone and neurotransmitter occurring in a wide variety of animals, including both vertebrates and invertebrates. In chemical structure, it is a phenethylamine.
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Epinephrine (INN) (IPA: [ˌɛpɪˈnɛfrən]) or adrenaline (European Pharmacopoeia and BAN) (IPA: [əˈdrɛnələn]
..... Click the link for more information.
Norepinephrine (INN)(abbr. norepi or NE) or noradrenaline (BAN) is a catecholamine and a phenethylamine with chemical formula C8H11NO3. The natural stereoisomer is L -(−)-(R)-norepinephrine.
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The central nervous system (CNS) represents the largest part of the nervous system, including the brain and the spinal cord. Together with the peripheral nervous system, it has a fundamental role in the control of behavior.
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In pharmacology, the term mechanism of action refers to the specific biochemical interaction through which a drug substance produces its pharmacological effect. A mechanism of action usually includes mention of the specific molecular targets to which the drug binds, such as an
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Diethylcathinone (also called Diethylpropion and Amfepramone), is a sympathomimetic stimulant drug marketed as an appetite suppressant. It is sold under the brand name Tenuate or Tenuate Dospan, and may also be known as Amfepramone.
..... Click the link for more information.
    Phendimetrazine (Bontril®) is a weight loss medication. Phendimetrazine is chemically related to amphetamines and is a Schedule III drug under the Convention on Psychotropic Substances.
    ..... Click the link for more information.
    The fight-or-flight response, also called hyperarousal or the acute stress response, was first described by Walter Cannon in 1915[1][2].
    ..... Click the link for more information.
    Food and Drug Administration (FDA) is an agency of the United States Department of Health and Human Services and is responsible the safety regulation of most types of foods, dietary supplements, drugs, vaccines, biological medical products, blood products, medical devices,
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    Dieting is the practice of ingesting food in a regulated fashion to achieve a particular objective. In many cases the goal is weight loss, but some athletes aspire to gain weight (usually in the form of muscle) and diets can also be used to maintain a stable body weight.
    ..... Click the link for more information.


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