Phentermine, a contraction for "
phenyl-
tertiary-butyl
amineAmines are organic compounds and functional groups that contain a basic nitrogen atom with a lone pair. Amines are derivatives of ammonia, wherein one or more hydrogen atoms have been replaced by a substituent such as an alkyl or aryl group. Important amines include amino acids, biogenic amines,...
", is an appetite suppressant of the
amphetamineAmphetamine is a psychostimulant drug that is known to produce increased wakefulness and focus in association with decreased fatigue and appetite. Amphetamine is related to drugs such as methamphetamine and dextroamphetamine, which are a group of potent drugs that act by increasing levels of...
and
phenethylaminePhenethylamine is a natural monoamine alkaloid, trace amine, and psychoactive drug with stimulant effects. In the mammalian central nervous system, phenethylamine is believed to function as a neuromodulator or neurotransmitter. It is biosynthesized from the amino acid phenylalanine by enzymatic...
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.
- Adipex P (Immediate release)
- Anoxine-AM
- Ionamin (Slow Release Resin, Australia, discontinued in the US)
- Duramine (Slow Release Resin, New Zealand, Australia & South Africa)
- Fastin
- Mirapront
- Obephen
- Obermine
- Obestin-30
- Phentremene
- Phentrol
- Phenterex
- Phentromin
- Pro-Fast SA
- Redusa
- Panbesy
- Phentermine Trenker
- Obenix
- Oby-Trim
- Teramine
- Zantryl
- Sinpet (MX)
- Supremin (PH)
- Umine (NZ)
- Weltmine (KP)
In 1959 phentermine first received approval from the FDA as an appetite suppressing drug.
Phentermine, a contraction for "
phenyl-
tertiary-butyl
amineAmines are organic compounds and functional groups that contain a basic nitrogen atom with a lone pair. Amines are derivatives of ammonia, wherein one or more hydrogen atoms have been replaced by a substituent such as an alkyl or aryl group. Important amines include amino acids, biogenic amines,...
", is an appetite suppressant of the
amphetamineAmphetamine is a psychostimulant drug that is known to produce increased wakefulness and focus in association with decreased fatigue and appetite. Amphetamine is related to drugs such as methamphetamine and dextroamphetamine, which are a group of potent drugs that act by increasing levels of...
and
phenethylaminePhenethylamine is a natural monoamine alkaloid, trace amine, and psychoactive drug with stimulant effects. In the mammalian central nervous system, phenethylamine is believed to function as a neuromodulator or neurotransmitter. It is biosynthesized from the amino acid phenylalanine by enzymatic...
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
- Ionamin (Slow Release Resin, Australia, discontinued in the US)
- Duramine (Slow Release Resin, New Zealand, Australia & South Africa)
- Fastin
- Mirapront
- Obephen
- Obermine
- Obestin-30
- Phentremene
- Phentrol
- Phenterex
- Phentromin
- Pro-Fast SA
- Redusa
- Panbesy
- Phentermine Trenker
- Obenix
- Oby-Trim
- Teramine
- Zantryl
- Sinpet (MX)
- Supremin (PH)
- Umine (NZ)
- Weltmine (KP)
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
fenfluramineFenfluramine is a drug that was part of the Fen-Phen anti-obesity medication . Also known as Pondimin, fenfluramine was introduced on the U.S. market in 1973. It is the racemic mixture of two enantiomers, dextrofenfluramine and levofenfluramine...
or
dexfenfluramineDexfenfluramine, 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. However, following multiple concerns about the cardiovascular side-effects of...
and became known as
Fen-PhenFen-phen was an anti-obesity medication 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, but were shown to cause potentially fatal pulmonary hypertension and heart valve...
.
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, it is classified as a
controlled substanceA 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 ....
in many countries. Internationally, phentermine is a schedule IV drug under the
Convention on Psychotropic SubstancesThe Convention on Psychotropic Substances is a United Nations treaty designed to control psychoactive drugs such as amphetamines, barbiturates, and psychedelics. During the 1960 such drugs became widely available. Government authorities opposed this for numerous reasons, arguing that along with...
. In the United States, it is classified as a Schedule IV controlled substance under the
Controlled Substances ActThe Controlled Substances Act 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. The CSA is the federal U.S. drug policy under which the manufacture, importation, possession, use and distribution of certain...
.
Mechanism of action
Phentermine, in doses clinically used, works on the hypothalamus portion of the brain to release
norepinephrineNoradrenaline or norepinephrine is a catecholamine with dual roles as a hormone and a neurotransmitter....
, a neurotransmitter or chemical messenger that signals a
fight-or-flight responseThe "fight-or-flight response", also called the "fight-or-flight-or-freeze response", the "fright, fight or flight response", "hyperarousal" or the "acute stress response", was first described by Walter Cannon in 1929....
, reducing hunger. Phentermine works outside the brain as well to release epinephrine or adrenaline causing fat cells to break down stored fat, but the principal basis of efficacy is hunger-reduction. At high doses, phentermine releases
serotoninSerotonin is a monoamine neurotransmitter. It is found extensively in the gastrointestinal tract of animals, and about 80 to 90 percent of the human body's total serotonin is located in the enterochromaffin cells in the gut, where it is used to regulate intestinal movements...
and
dopamineDopamine is a neurotransmitter occurring in a wide variety of animals, including both vertebrates and invertebrates. In the brain, this phenethylamine functions as a neurotransmitter, activating the five types of dopamine receptors — D
1, D
2, D
3, D
4, and...
as well, but such doses are never used in clinical medicine.
Dosing and administration
Generally, it is recommended by the
Food and Drug AdministrationThe Food and Drug Administration is a Government agency of the United States Department of Health and Human Services and is responsible for regulating and supervising the safety of foods, tobacco products, dietary supplements, Medication drugs, vaccines, Biopharmaceutical, blood transfusion,...
(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
dietingDieting is the practice of ingesting food in a regulated fashion to achieve or maintain a controlled weight. In most cases the goal is weight loss in those who are overweight or obese, but some athletes aspire to gain weight...
and exercise.
Contraindications and warnings
- Patients with the following should not use Phentermine:
- An allergy
Allergy is a disorder of the immune system often also referred to as atopy. Allergic reactions occur to normally harmless environmental substances known as allergens; these reactions are acquired, predictable, and rapid. Strictly, allergy is one of four forms of hypersensitivity and is called type...
to any ingredient in Phentermine or other sympathomimetics (eg, pseudoephedrinePseudoephedrine is a sympathomimetic amine commonly used as a decongestant. The salts pseudoephedrine hydrochloride and pseudoephedrine sulfate are found in many over-the-counter preparations either as single-ingredient preparations, or more commonly in combination with antihistamines, paracetamol...
)
- Are also taking dexfenfluramine
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. However, following multiple concerns about the cardiovascular side-effects of...
, fenfluramineFenfluramine is a drug that was part of the Fen-Phen anti-obesity medication . Also known as Pondimin, fenfluramine was introduced on the U.S. market in 1973. It is the racemic mixture of two enantiomers, dextrofenfluramine and levofenfluramine...
, furazolidoneFurazolidone is an antibacterial. It is marketed by Roberts Laboratories under the brand name Furoxone and by GlaxoSmithKline as Dependal-M.-Uses:It is used to treat diarrhoea and enteritis caused by bacteria or protozoan infections....
, guanadrelGuanadrel is an antihypertensive agent.-Mechanism of action:Guanadrel is a postganglionic adrenergic blocking agent. Uptake of guanadrel and storage in sympathetic neurons occurs via the norepinephrine pump; guanadrel slowly displaces norepinephrine from its storage in nerve endings and thereby...
, guanethidineGuanethidine is an antihypertensive drug that reduces the release of catecholamines, such as noradrenaline. Its mechanism is inhibition of the Na+ATPase dependent pump.-Side effects:...
, or have taken a monoamine oxidase inhibitorMonoamine oxidase inhibitors are a class of powerful antidepressant drugs prescribed for the treatment of depression. They are particularly effective in treating atypical depression, and have also shown efficacy in smoking cessation....
(MAOI) (eg, phenelzine) in the last 14 days
- Have severe high blood pressure, an overactive thyroid, glaucoma
Glaucoma is a group of diseases that affect the optic nerve and involves a loss of retinal ganglion cells in a characteristic pattern. It is a type of optic neuropathy. Raised intraocular pressure is a significant risk factor for developing 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
Although the term substance can refer to any physical matter, substance abuse has come to refer to the overindulgence in and dependence of a drug or other chemical leading to effects that are detrimental to the individual's physical and mental health, or the welfare of others.]The disorder is...
- 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
- Guanadrel(Hylorel) or guanethidine(Ismelin) because their effectiveness may be decreased by phentermine
- Antacids: Antacids may decrease the excretion of phentermine.
- Carbonic anhydrase inhibitors (acetazolamide, dichlorphenamide, methazolamide): Carbonic anhydrase inhibitors may decrease the excretion of phentermine.
Side effects
Generally, phentermine appears to be relatively well tolerated. 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 pressureBlood pressure is the pressure exerted by circulating blood on the walls of blood vessels, and is one of the principal vital signs. During each heartbeat, BP varies between a maximum and a minimum pressure...
and
heart rateHeart rate is determined by the number of heartbeats per unit of time, typically expressed as beats per minute , it can vary with as the body's need for oxygen changes, such as during exercise or sleep. The measurement of heart rate is used by medical professionals to assist in the diagnosis and...
. It may also cause
palpitationA palpitation is an abnormal awareness of the beating of the heart, whether it is too slow, too fast, irregular, or at its normal frequency. It can be caused by ectopic beat, which is a more specific diagnosis....
s, restlessness, and
insomniaInsomnia is a symptom of any of several sleep disorders, characterized by persistent difficulty falling asleep or staying asleep despite the opportunity. Insomnia is a symptom, not a stand-alone diagnosis or a disease. By definition, insomnia is "difficulty initiating or maintaining sleep, or both"...
. Additionally, phentermine has the potential to cause physical and psychological dependence.
More common
- Insomnia
- Hypertension
- Irritability
- Nervousness
- Euphoria
- Dry mouth
- Unpleasant taste
- Blurred vision
- Heartburn/Acid reflux
- Changes in libido
- Clumsiness
- Confusion
- Diarrhea
- Dizziness
- Headache
- Arrhythmia
- Nausea or vomiting
- Psychosis
- Skin rash or itching
- Stomach pain
- Fatigue
Less common
- Convulsions (seizures)
- Dizziness
- Fever
- Hallucinations
- Hostility with urge to attack
- Irregular blood pressure
- Lightheadedness or fainting
- Periods of mania followed by period of depression
- Tremors, trembling or shaking
- Overactive reflexes
- Panic
- Restlessness
- Severe nausea, vomiting or diarrhea
- Stomach cramps
- Weakness
External links