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.