Phentermine
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Phentermine |
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Systematic
(IUPAC)
name |
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2-methyl-1-phenyl-propan-2-amine |
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Identifiers |
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Chemical
data |
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C10H15N |
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149.233
g/mol |
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Pharmacokinetic
data |
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Peak plasma levels occur within 1
to 3 hours. Absorption is usually complete by 4 to 6 hours |
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Approximately
96.3% |
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hepatic |
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16
to 31 hours |
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Urinary
elimination |
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Therapeutic
considerations |
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C(United
States); ? (Australia) |
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C-IV
(US) |
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Oral |
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Phentermine is a phenethylamine primarily used as an appetite
suppressant. 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).
Contents
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[edit]
History
Phentermine is one of two
drugs in the Fen-phen anti-obesity medication, the other being fenfluramine or dexfenfluramine. Fenfluramine was withdrawn from
the U.S. market in 1997 after reports of valvular
heart disease and pulmonary
hypertension.
Phentermine is still available
by itself in most countries, including the U.S. However, because it is similar
to the 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 (PDF file). In the
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Mechanism of
action
Phentermine, as many other
prescription drugs, works with neurotransmitters in the brain. It is a
centrally-acting stimulant chemically related to the amphetamines. 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
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 suppresants 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.
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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 (PMID 11054601). Due to the risk of insomnia, it is generally recommended that the drug be
taken either before breakfast or 1-2 hours after breakfast.
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Side effects
Generally, phentermine
appears to be relatively well tolerated.[1] It can produce side effects
consistent with its chycardia]], increased alertness, but the incidence and
magnitude of these appear to be less than with the amphetamines. Because
phentermine acts through sympathomimetic pathways, the drug ug on a
long-term basis may develop euphoria and a psychological
addiction
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Contraindications
Phentermine should
generally be avoided in patients with:
- Agitation
- Allergy/Hypersensitivity to other sympathomimetic amines
- Atherosclerosis
- Cardiovascular disease
- Glaucoma
- High blood pressure
- Hyperthyroidism
- Previous 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 inhibitors.
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Internet Notoriety
Recently, phentermine has
drawn the ire of many internet users. The medication is one of the most
commonly used terms in spam e-mails and bulletin board postings
by bots.
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Related Article
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External links
- MedLine
Plus - Phentermine
- International Programme on
Chemical Safety - Phentermine
- DrugBank:Phentermine
- TOXNET
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References
and End Notes
- ^ Nelson DL,