Amphetamines are a class of central nervous system stimulants with a similar chemical structure, including amphetamine, methamphetamine, dextroamphetamine, ephedrine, and others. Generally, these drugs generate emotional, cognitive, and physical effects, such as increased energy and focus and decreased appetite. They may be prescribed legally for the treatment of ADHD, narcolepsy, or other conditions; they are also used illegally to improve performance, lose weight, or to generate a “high.”
Many amphetamines are Schedule II stimulants, which means they have a high potential for abuse and are legally available only through a prescription. When used for medical purposes, the doses are much lower than those typical among abusers of the drugs.
Of the amphetamines, methamphetamine likely has the largest potential for abuse. Abuse of methamphetamine can cause long-lasting brain damage along with other problems. The drug is typically made in clandestine laboratories with relatively inexpensive over-the-counter ingredients.
Methamphetamine is commonly known as "speed," "meth," or "chalk." In its smoked form, it is often referred to as "ice," "crystal," "crank," and "glass." It is a white, odorless, bitter-tasting crystalline powder that easily dissolves in water or alcohol. It was developed early in the 20th century from its parent drug, amphetamine, and was used originally in nasal decongestants and bronchial inhalers. Methamphetamine causes increased activity, decreased appetite, and a general sense of well-being. It starts working quickly, and its effects can last six to eight hours. After the initial rush, there is typically a state of high agitation that in some individuals may lead to violent behavior.
Methamphetamine is structurally similar to the neurotransmitter dopamine. Though its behavioral and physiological effects are similar to those of cocaine, there are some major differences in the basic mechanisms of how these drugs work at the cellular level. But methamphetamine, like cocaine, results in an accumulation of the neurotransmitter dopamine, which appears to produce the stimulation and feelings of euphoria experienced by the user. Methamphetamine has a much longer duration of action and a larger percentage of the drug remains unchanged in the body. This results in methamphetamine being present in the brain longer, which ultimately leads to prolonged stimulant effects.
As with similar stimulants, methamphetamine is most often used in a "binge and crash" pattern. Because the pleasurable effects disappear even before the drug concentration in the blood falls significantly, users try to maintain the high by bingeing on the drug. In some cases, abusers indulge in a form of bingeing known as a "run," forgoing food and sleep while continuing abuse for up to several days.
Symptoms of Use
Using amphetamines other than as prescribed may induce some of the following symptoms, over the short or long term:
- Enhanced mood and body movement
- Increased wakefulness, physical activity
- Increased respiration
- Dilated pupils
- Reduced appetite
- Increased blood pressure
- Rapid/irregular heartbeat
- Cardiovascular collapse, which may cause death
- Changes in brain structure and function, including damage to brain cells containing serotonin
- Weight loss
- Memory loss
- Psychosis, paranoia, hallucinations
- Repetitive motor activity, Parkinson's-like symptoms
- Damage to nerve cells, which may cause strokes
- Cardiovascular collapse, which may cause death
In certain cases, psychotic symptoms can last for months or years after methamphetamine abuse has ceased. Stress has been shown to precipitate spontaneous recurrence of methamphetamine psychosis in formerly psychotic methamphetamine abusers.
Increased HIV and hepatitis B and C transmission are possible related consequences of increased methamphetamine abuse, not only in individuals who inject the drug, but also in non-injecting methamphetamine abusers. Among injection drug users, infection with HIV and other infectious diseases is spread primarily through the use of contaminated syringes, needles, or other paraphernalia by more than one person. The intoxicating effects of methamphetamine can also alter judgment and inhibition, which may lead people to engage in unsafe behaviors. Methamphetamine abuse may also worsen the progression of HIV and its consequences. In animal studies, methamphetamine increased viral replication; in human methamphetamine abusers, HIV caused greater neuronal injury and cognitive impairment compared with non-drug abusers.
When used illegally, pure amphetamines may be mixed with other substances—such as sugar, glucose, or bi-carb soda—that can be poisonous. This may cause collapsed veins, tetanus, abscesses and damage to the heart, lungs, liver, and brain. Amphetamine users may also use other drugs inappropriately to manage the side effects of amphetamines. Benzodiazepines, for example, are anti-anxiety agents that may be used to help an individual sleep, but that can also be addictive.
Clinical diagnosis for amphetamine use falls under the general category of Stimulant Use Disorder. According to DSM-5, in order for a diagnosis of Stimulant Use Disorder to be made, an individual must demonstrate a pattern of amphetamine, cocaine, or other stimulant use leading to clinically significant impairment or distress, as manifested by at least two of the following symptoms occurring within a 12-month period:
- Taking the stimulant in larger dosages and/or for a longer period of time than intended
- Desiring to reduce stimulant use, and/or making failed efforts to do so
- Spending a large amount of time procuring, using, or recovering from the effects of the stimulant
- Experiencing a strong desire or urge to use the stimulant
- Demonstrating the inability, due to stimulant use, to maintain obligations for one's job, school, or home life
- Continuing to use the stimulant in the face of social/interpersonal problems that result from, or are made worse by, the use of the stimulant
- Prioritizing stimulant use to such an extent that social, occupational, and recreational activities are either given up on completely or are reduced drastically
- Repeatedly using the stimulant in situations in which it is physically hazardous
- Continuing to use the stimulant even when the individual knows that it is causing or exacerbating physical and psychological problems
- Tolerance, as shown by one of the following:
- Intoxication requires considerably greater amounts of stimulant use than it did previously
- The same dose of the stimulant over the same amount of time results in considerably weaker effects
- Withdrawal, as shown by one of the following:
- Individual displays withdrawal symptoms and characteristics of the stimulant
- Symptoms of withdrawal diminish as a result of the use of the stimulant (or similar substances)
The tolerance and withdrawal criteria are not considered to be met if the stimulant is used only under appropriate medical supervision.
The estimated 12-month prevalence of a stimulant use disorder involving amphetamines is 0.2 percent among U.S. adults, according to the DSM-5.
While the effects of amphetamines are almost immediate, tolerance builds quickly, which frequently increases the amount needed to produce the desired effect. During periods of nonuse, the user may recall the feeling of euphoria produced by the drug and desire to take it again.
The most effective treatments for amphetamine addiction are cognitive behavioral intervention and contingency management models. The Matrix Model, for example, is a comprehensive behavioral treatment approach that combines behavioral therapy, family education, individual counseling, 12-step support, drug testing, and encouragement for non-drug-related activities; it has been shown to be effective in reducing amphetamine abuse. Contingency management interventions, which provide tangible incentives in exchange for engaging in treatment and maintaining abstinence, have also been shown to be effective.
There are no specific medications that counteract the effects of amphetamines or that prolong abstinence from and reduce the abuse of amphetamines. However, there are a number of medications that are FDA-approved for other illnesses that might also be useful in treating amphetamine addiction. Recent findings indicate that bupropion, the anti-depressant marketed as Wellbutrin, may reduce a methamphetamine-induced high as well as drug cravings elicited by drug-related cues. This medication and others are currently in clinical trials, while new compounds are being developed and studied in preclinical models.