Amphetamine

views updated

Amphetamine

Amphetamine was first synthesized, or made, in a laboratory in 1887. However, scientists did not know of its effects as a stimulant on the central nervous system (the brain and spinal cord) until the early 1930s. In the 1880s cocaine projects were introduced as risk free. In the same way, the medical profession promoted amphetamine as an effective cure for a wide range of ills without any risk of addiction. Doctors recommended it to treat alcohol hangovers, depression, and vomiting during pregnancy, and to help patients lose weight. Public interest grew in this supposed miracle drug, which was inexpensive, easy to obtain, and had long-lasting effects. Beginning in the 1930s, amphetamines became drugs of abuse.

Drugs created from amphetamine, such as methamphetamine, became available for therapeutic uses in both oral (to be taken by mouth) and intravenous (to be injected) form. Despite occasional bad reactions, Americans—college students, athletes, truck drivers, and housewives—took enormous quantities of amphetamines in the 1940s and 1950s. The medical community still did not recognize the drugs' abuse potential, that is, the likelihood that they would be abused. DuringWorld War II, the U.S., British, German, and Japanese militaries provided amphetamines, including methamphetamine, to soldiers in combat in order to counteract fatigue, to increase alertness during battle and night watches, to increase endurance, and to elevate mood. Approximately 200 million Benzedrine (amphetamine) tablets were dispensed to the U.S. Armed Forces during World War II. In fact, much of the research on the effects of the amphetamines on performance was carried out on enlisted personnel during this period.

Since 1945, amphetamines and cocaine have each at different times been the most popular illicit stimulant. The first major amphetamine epidemic in the United States peaked in the mid-1960s. Approximately 13.5 percent of the university population in 1969 had used amphetamines at least once. By 1978, amphetamine use declined substantially as cocaine use increased. In the early 1990s, use of amphetamines began to rise again, peaking around 1997, then declined slightly before leveling off. The major amphetamine of concern in the United States in the 1990s was methamphetamine, with pockets of "ice" (smoked methamphetamine) abuse. In 2001 use of methamphetamine continued to increase, although the rate of increase appeared to be gradually slowing.

Amphetamines are now controlled under Schedule II of the Controlled Substances Act. Substances in Schedule II—including the stimulants amphetamine, methamphetamine, cocaine, methylphenidate, and phenmetrazine—have a high potential for abuse but also have accepted medical uses in the United States.

Biological Responses

The amphetamines act by increasing concentrations of brain chemicals known as neurotransmitters. The two main neurotransmitters, dopamine and norepinephrine, accumulate in the spaces between brain cells, known as the neuronal synapse. Amphetamines increase the release of dopamine and norepinephrine and block their absorption of uptake into brain cells. Cocaine also blocks uptake of these transmitters but does not increase their release. Amphetamine continues to act in the body for about ten hours, compared to one hour for cocaine and five hours for methamphetamine.

Amphetamines increase heart rate, respiration, and blood pressure. High doses can cause cardiac arrhythmias (irregular heartbeat). In addition, the amphetamines help suppress rapid eye movement sleep—the stage of sleep associated with dreaming—and total sleep. A single moderate dose of amphetamine generally produces the following effects in humans:

an increase in activity and talkativeness
euphoria and a general sense of well-being
decrease in food intake
decrease in fatigue

Higher doses can produce repetitive motor activity. This means that the user performs a particular action repeatedly, such as tapping his or her fingers or jiggling limbs uncontrollably. Very high doses can lead to convulsions, coma, and death.

Medical Uses

Doctors frequently prescribe amphetamines to treat narcolepsy, obesity, and attention deficit disorder.

Narcolepsy. People with narcolepsy have sudden attacks of sleep. In large doses over long periods of time, amphetamines can generally prevent these attacks. Interestingly, few narcolepsy patients develop tolerance to the effects of these drugs, and most stay on the same dose for years.

Obesity. Because amphetamines are extremely effective appetite suppressants, doctors prescribe them extensively to treat obesity. However, many patients rapidly develop tolerance to the appetite-suppressant effects. After several weeks of use, the patient must take a higher dose to achieve the same effect achieved with the initial dose. Taking high doses over long periods of time can result in toxic side effects: insomnia, irritability, increased heart rate and blood pressure, and tremulousness (shaking). Therefore, these drugs should be taken only for relatively short periods of time (four to six weeks).

Studies show that amphetamines are not effective at helping a person maintain weight loss. Rapid weight gain occurs when he or she stops taking them. The lack of long-term effectiveness, along with the dependence-producing effects of amphetamines, makes them a poor choice for maintaining weight loss.

Attention-Deficit/Hyperactivity Disorder. For children with attention-deficit/hyperactivity disorder, amphetamines (such as Ritalin) can dramatically reduce restlessness and distractibility and lengthen attention span. Those who support the use of amphetamines for this disorder recommend limiting the dose and the duration of treatment to prevent side effects.

The Effects on Behavior

According to research reports, amphetamines do not directly enhance performance. Scientists believe that amphetamines' other effects, such as reducing fatigue or boredom and increasing alertness, are the cause of any improvements in performance.

Trained athletes experience only very small improvements in performance when taking amphetamines. However, studies suggest that even these very small changes can result in the 1 to 2 percent improvement that makes the difference in a close athletic competition. As a result, some athletes take stimulants before athletic events, particularly those calling for strenuous activity over long periods, such as bicycle racing. But taking amphetamines for this purpose presents serious risks, including hyperthermia (elevated body temperature), collapse, and even death.

Amphetamines can produce changes in a person's moods. Users report increased self-confidence, elation, euphoria, friendliness, and generally positive feelings. However, users who take repeated doses develop tolerance to these mood-elevating effects. The user must take increasingly larger amounts of amphetamine to achieve the same effect. Thus the mood-elevating effect is closely related to abuse.

Experienced stimulant users, given a variety of stimulant drugs, often cannot tell the difference between one drug or another. Cocaine, amphetamine, methamphetamine, and methlyphenidate all appear to have similar effects. The major difference is in how long the drugs' effects last.

Side Effects

A major side effect of long-term amphetamine use in humans is a psychosis that resembles schizophrenia . In one study, volunteers with no histories of psychosis took an amphetamine drug for one to five days. Five of the six subjects developed paranoid psychosis, which cleared when the drug was discontinued. Unless the user continues to take the drug, the psychosis usually ends within a week, although it is possible that symptoms will keep occurring. The symptoms of amphetamine psychosis include feelings of being persecuted, hyperactivity and excitation, hallucinations—seeing and hearing things that are not real—and changes in body image.

Amphetamine abusers taking repeated doses of the drug can develop repetitive behavior patterns that continue for hours at a time. These can take the form of constant cleaning, taking apart small appliances over and over again, or picking at wounds. Stopping amphetamine use after long-term high doses generally results in loss of energy, depression, and abnormal sleep patterns. These symptoms may be due to the long-term lack of sleep and reduced food intake typical of chronic use.

Animals given unlimited access to amphetamine will self-administer it repeatedly. Most will continue self-administration until they die. Animals maintained on high doses of amphetamines develop tolerance to many of the damaging effects. They also develop irreversible damage in some parts of the brain, including long-lasting depletion of dopamine.

Abuse

Amphetamines, like other stimulants, are generally abused in binges. People take the drug repeatedly for some period of time—usually every three or four hours for three or four days. Then, during a crash period, the user sleeps, eats, and takes no drug at all. As tolerance develops, the user takes higher doses. Stopping amphetamine use suddenly usually results in depression. Mood generally returns to normal within a week, although craving for the drug can last for months. There is little evidence for the development of physical dependence to the amphetamines. Although some experts view the crash—with low energy, depression, exhaustion, and increased appetite—that can follow the amphetamine binge as a withdrawal syndrome, others believe that the symptoms can also be related to the effects of chronic stimulant use. In other words, during the binge, users have not slept or eaten much, resulting in depression, exhaustion, and hunger when the binge ends.

Treatment of Amphetamine Abuse

As with cocaine abuse, the most promising forms of treatment for amphetamine abuse include behavioral therapy, prevention of relapse (return to drug use), rehabilitation (for example, vocational, educational, and social-skills training), and psychotherapy. Few studies have tested medications for amphetamine abuse. Those that have been done report no success in preventing a return to amphetamine use.