Amphetamine

Amphetamine (alpha-methyl-phenethylamine), is a synthetic central nervous system stimulant which is used, today, to treat a very limited spectrum of medical disorders. These include narcolepsy, improving consciousness after traumatic brain injury, and refractory cases of attention-deficit hyperactivity disorder. Narcolepsy is a rare disorder, and the use of amphetamines in treating attention deficit disorder is approved only in low doses and, generally, only when first and second line treatments fail. This restricted use of the drug in medicine today is very different from its frequent prescription for a wide range of purposes in past decades. As with other addictive drugs of high potential for abuse, regulation as a controlled substance in medicine came only after the dangerous side-effects of the drug became undeniable.

When amphetamines were first synthesized, in 1887, they were promoted for their ability to suppress the need to eat or sleep and hoped to be an aid for soldiers in battle. Later, in the 1950's and 1960's, amphetamines were widely prescribed in Europe and North America for weight loss and as an "energy aid". At that time, amphetamines were even prescribed for pregnant women in order to limit weight gain. Although rumors of dependency, addiction, and "breakdowns" attributed to amphetamine use were public in those years, the drug was easily available by prescription for a number of indications. By the 1970's, the marked psychological dependency for chronic use of amphetamines became clear, along with the ability of the drug , in high doses, to cause the outward signs of many symptoms of paranoid schizophrenia in users. These include auditory hallucinations, paranoid ideation and thought disorders. These drugs became carefully regulated controlled substances in almost every country of the world by the 1980's. Additionally, although weight loss had been confirmed as facilitated during amphetamine use, weight gain at cessation of administration of the drug had also been confirmed, and no long term benefit in the treatment of obesity could be demonstrated. The treatment of obesity with amphetamine is aggravated by decreased glucose tolerance in many users, especially diabetics.

Illicit production and use of amphetamines occurs on a widescale basis in many nations, typically in the form of amphetamine sulfate synthesized from phenylpropanolamine. In addition, prescription amphetamines are subject to diversion and are one of the most frequently-abused drugs in high schools and colleges.

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Toxicity

Patients with acute toxicity from amphetamines may have symptoms of psychosis, disorientation, temporary symptoms associated with schizophrenia, aggression, delusions, lock-jaw, diarrhea, palpitations, arrhythmia, syncope, hyperpyrexia, and hyperreflexia progressing to convulsions and coma. Patients with chronic use of amphetamines develop a rapid tolerance to the drug and may have to increase the dose to reach the desired effect and eventually develop addiction. Patients that develop addiction show symptoms of restlessness, anxiety, depression, insomnia, and suicidal behavior. A urine drug screen can be performed to determine the presence of amphetamines. Patients may need to be hospitalized. Supportive therapy is important. Cooling blankets may be used for hyperthermia. Sedation may be obtained with lorazepam or diazepam. Haloperidol may be given for agitation and delusions. Hypertension and arrhythmias should be treated.

Chemistry

Amphetamine was first synthesized in 1887 by the Romanian chemist Lazăr Edeleanu at the University of Berlin, who called it "phenylisopropylamine". Gordon Alles, a California biochemist operating independently of any university, discovered its sympathomimetic and central nervous system stimulant properties in 1929. Amphetamine is a chiral compound. The racemic mixture can be divided into its optical antipodes: levo- and dextro-amphetamine. Amphetamine is the parent compound of its own structural class, comprising a broad range of psychoactive derivatives, e.g., MDMA (Ecstasy) and the N-methylated form, methamphetamine. Amphetamine is a homologue of phenethylamine.

Traditionally the medical drug came in the racemic salt-form rac-amphetamine sulfate (rac = levo- and dextro-form in equal amounts). In the United States, pharmaceutical products containing solely rac-amphetamine are no longer manufactured. Today, dextroamphetamine sulphate is the predominant form of the drug used; it consists entirely of the d-isomer. Attention disorders are often treated using Adderall or generic-equivalent formulations of mixed amphetamine salts that contain both d/l-amphetamine and d-amphetamine in the sulfate and saccharate forms mixed to a final ratio of 3 parts d-amphetamine to 1 part l-amphetamine.

Pharmacology

Dextroamphetamine, the eutomer of amphetamine, exhibits its mode of central action via release and reuptake inhibition of the monoamine neurotransmitters norepinephrine (NE) and dopamine (DA), but not serotonin (5-HT). Its activity at the vesicular monoamine transporter VMAT2 is of crucial importance in the release process.

Medicinal use

Indicated for: Diet suppressant ADD ADHD Narcolepsy Treatment-resistant depression Recreational uses: Stimulant Other uses: Used by the US military to combat fatigue and increase wakefulness

Contraindications: CNS Stimulants MAOI use

Side effects: Dizziness Tachycardia Sweating Decrease in appetite/weight loss Euphoria followed by depression Insomnia Anger Aggressiveness Hostility Cardiovascular: Bronchodilator Ear, nose, and throat: Decongestant Eye: Mydriasis (Pupil dilation) Gastrointestinal: Diarrhoea Musculoskeletal: Muscle aches/cramps Neurological: Dopamine Agonist Norepinephrine Agonist Respiratory: Bronchodilator

The experimental medical use of amphetamine began in the early 1930s. In approximately 1933 it was introduced as an over-the-counter decongestant product called the Benzedrine Inhaler, a tube containing volatile amphetamine base that would release the drug in vapor form when inserted in the nostril. For internal use it was introduced as the pharmaceutical Benzedrine sulfate tablets in 1936 and marketed especially for minor depression. During the Second World War the drug was used by the Allied militaries, especially the air forces, to fight fatigue and increase alertness among servicemen; the German and Japanese militaries similarly employed methamphetamine. After decades of reports of abuse, the FDA banned amphetamine inhalers, and limited the drug to prescription use in 1959, but illegal use became common.

Along with methylphenidate (Ritalin, Concerta, etc.), amphetamine is one of the standard treatments for ADHD. Beneficial effects for ADHD can include improved impulse control, improved concentration, decreased sensory overstimulation, and decreased irritability. These effects can be dramatic, particularly in young children. The ADHD medication Adderall is composed of four different amphetamine salts, and Adderall XR is a timed release formulation of these same salt forms.

When used within the recommended doses, side-effects like loss of appetite tend to decrease over time. However, amphetamines last longer in the body than methylphenidate (Ritalin, Concerta, etc.), and tend to have stronger side-effects on appetite and sleep.

Amphetamines are also a standard treatment for narcolepsy as well as other sleeping disorders. They are generally effective over long periods of time without producing addiction or physical dependence.

Amphetamines are sometimes used to augment anti-depressant therapy in treatment-resistant depression.

Medical use for weight loss is still approved in some countries, but is regarded as obsolete and dangerous in, for example, the United States.

Performance-enhancing use

Amphetamines are usually not used by athletes in sports involving extreme cardiovascular efforts, as methamphetamine and amphetamine put a great deal of additional stress on the heart.

The United States Air Force used amphetamines (Dexedrine) as stimulants for pilots, calling them "go-pills." However, recent developments in designing ampakines, specifically modafinil, allow the pilots to stay alert without the paranoia and discomfort associated with dextroamphetamine. After a mission, the Air Force issues a "no-go pill" (Ambien or Temazepam) to help the pilot sleep.

Amphetamines have been popular among some truck drivers, construction workers, and factory workers whose jobs require long or irregular shift work or automatic, repetitive tasks. It is for this reason that they are sometimes labeled a "redneck drug." They are also used by white-collar workers trying to stay alert during long hours of multitasking, and by students hoping to improve their academic performance. There has also been at least one report of the coercive administration of amphetamines to cannery workers in Thailand, in order to enhance productivity (Seabrook, 1996).

The drug was also popular in the UK during the 1960s and 70s, playing a large part in Mod culture and later used by punks to continue dancing through the night.

Effects of use

Amphetamines release stores of norepinephrine and dopamine from nerve endings by converting the respective molecular transporters into open channels. Amphetamine also releases stores of serotonin from synaptic vesicles. Like methylphenidate (Ritalin), amphetamines also prevent the monoamine transporters for dopamine and norepinephrine from recycling them (called reuptake inhibition), which leads to increased amounts of dopamine and norepinephrine in synaptic clefts.

These combined effects rapidly increase the concentrations of the respective neurotransmitters in the synaptic cleft, which promotes nerve impulse transmission in neurons that have those receptors.

Physiological effects

• Short-term physiological effects include decreased appetite, increased stamina and physical energy, increased sexual drive/response, involuntary bodily movements, increased perspiration, hyperactivity, jitteriness, nausea, itchy, blotchy or greasy skin, increased heart rate, irregular heart rate, increased blood pressure, and headaches. Fatigue can often follow the dose's period of effectiveness. Overdose can be treated with chlorpromazine. [1]

• Long-term abuse or overdose effects can include tremor, restlessness, changed sleep patterns, anxiety and increase in pre-existing anxiety, poor skin condition, hyperreflexia, tachypnea, gastrointestinal narrowing, and weakened immune system. Fatigue and depression can follow the excitement stage. Erectile dysfunction (Wizz dick), heart problems, stroke, and liver, kidney and lung damage can result from prolonged use. When snorted, amphetamine can lead to a deterioration of the lining of the nostrils.

Psychological effects

• Short-term psychological effects can include alertness, euphoria, increased concentration, rapid talking, increased confidence, increased social responsiveness, nystagmus (eye wiggles), hallucinations, and loss of REM sleep the night after use.

• Long-term psychological effects can include insomnia, mental states resembling schizophrenia, aggressiveness (not associated with schizophrenia), addiction or dependence with accompanying withdrawal symptoms, irritability, confusion, and panic. Chronic and/or extensively-continuous use can lead to amphetamine psychosis, which causes delusions and paranoia, but this is uncommon when taken as prescribed. Amphetamine is highly-psychologically addictive, and, with chronic use, tolerance develops very quickly. Withdrawal is, although not physiologically threatening, an unpleasant experience (including paranoia, depression, difficult breathing, dysphoria, gastric fluctuations and/or pain, and lethargia). This commonly leads chronic users to re-dose amphetamine frequently, explaining tolerance and increasing the possibility of addiction.

Addiction

Tolerance is developed rapidly in amphetamine use, therefore increasing the amount of the drug that is needed to satisfy the addiction. Many abusers will repeat the amphetamine cycle by taking more of the drug during the withdrawal. This leads to a very dangerous cycle and may involve the use of other drugs to get over the withdrawal process.

Effects of exposure during gestation

In clinical studies that describe the characteristics of infants born to mothers who abuse amphetamines, the mothers generally have other characteristics, such as smoking during pregnancy and a lack of prenatal care, that complicate analysis. However, there have been findings of certain abnormailty in infants even when these factors are controlled for, such as a significant tendency for babies to be small for gestational age. When mothers admit to using methamphetamine for periods during all three trimesters of pregnancy, their infants have been found to have a significant abnormality in head size, with a smaller than normal head circumference - even when babies were born full-term.

Legal issues

• In the United Kingdom, amphetamines are regarded as Class B drugs. The maximum penalty for unauthorised possession is three months' imprisonment and a £2,500 fine.
• In the United States, amphetamine and methamphetamine are Schedule II controlled drugs, classified as a CNS (Central Nervous System) Stimulant. A Schedule II drug is classified as one that: has a high potential for abuse, has a currently-accepted medical use and is used under severe restrictions, and has a high possibility of severe psychological and physiological dependence.

Internationally, amphetamine is a Schedule II drug under the Convention on Psychotropic Substances.