Methamphetamine is a powerful central nervous system stimulant. It often is classed together with amphetamines as an amphetamine-type stimulant (ATS). Forms in which it is produced include powder, pills, base, or as a high-potency re-crystallized powder. Meth can be inhaled, smoked, injected, or swallowed, depending on the form.
Methamphetamine use increases energy and alertness and decreases appetite. An intense rush is felt, almost instantaneously, when a user smokes or injects methamphetamine. Snorting methamphetamine affects the user in approximately 5 minutes, whereas oral ingestion takes about 20 minutes for the user to feel the effects. The intense rush and high felt from methamphetamine results from the release of high levels of dopamine into the section of the brain that controls the feeling of pleasure. The effects of methamphetamine can last up to 12 hours. Side effects include convulsions, dangerously high body temperature, stroke, cardiac arrhythmia, stomach cramps, and shaking.
Chronic use of methamphetamine can result in a tolerance for the drug. Consequently, users may try to intensify the desired effects by taking higher doses of the drug, taking it more frequently, or changing their method of ingestion. Some abusers, while refraining from eating and sleeping, will binge, also known as "run," on methamphetamine. During these binges, users will inject as much as a gram of methamphetamine every 2 to 3 hours over several days until they run out of the drug or are too dazed to continue use.
Chronic methamphetamine abuse can lead to psychotic behavior including intense paranoia, visual and auditory hallucinations, and out-of-control rages that can result in violent episodes. Chronic users at times develop sores on their bodies from scratching at "crank bugs," which describes the common delusion that bugs are crawling under the skin. Long-term use of methamphetamine may result in anxiety, insomnia, and addiction.
After methamphetamine use is stopped, several withdrawal symptoms can occur, including depression, anxiety, fatigue, paranoia, aggression, and an intense craving for the drug. Psychotic symptoms can sometimes persist for months or years after use has ceased.