"Methamphetamine is a very addictive stimulant drug. It can be smoked, injected, inhaled, or taken by mouth. It has many street names, such as speed, meth, and chalk. Methamphetamine hydrochloride, the crystal form inhaled by smoking, is referred to as ice, crystal, glass, and tina. Methamphetamine affects the brain and can create feelings of pleasure, increase energy, and elevate mood. Abusers may become addicted quickly, needing higher doses more often. Adverse health effects include irregular heartbeat, increased blood pressure, and a variety of psychological problems. Long-term effects may include severe mental disorders, memory loss, and severe dental problems.\n\nMethamphetamine is a central nervous system stimulant drug that is similar in structure to amphetamine. Due to its high potential for abuse, methamphetamine is classified as a Schedule II drug and is available only through a prescription that cannot be refilled. Although methamphetamine can be prescribed by a doctor, its medical uses are limited, and the doses that are prescribed are much lower than those typically abused. Most of the methamphetamine abused in the United States comes from foreign or domestic superlabs, although it can also be made in small, illegal laboratories, where its production endangers the people in the labs, neighbors, and the environment.\n\nMethamphetamine is a white, odorless, bitter-tasting crystalline powder that easily dissolves in water or alcohol and is taken orally, intranasally by snorting the powder, by needle injection, or by smoking. Methamphetamine increases the release and blocks the reuptake of the brain chemical, or neurotransmitter, dopamine, leading to high levels of the chemical in the brain. Dopamine is involved in reward, motivation, the experience of pleasure, and motor function. Methamphetamine's ability to release dopamine rapidly in reward regions of the brain produces the intense euphoria, or rush, that many users feel after snorting, smoking, or injecting the drug.\n\nChronic methamphetamine abuse significantly changes how the brain functions. Noninvasive human brain imaging studies have shown alterations in the activity of the dopamine system that are associated with reduced motor skills and impaired verbal learning. Recent studies in chronic methamphetamine abusers have also revealed severe structural and functional changes in areas of the brain associated with emotion and memory, which may account for many of the emotional and cognitive problems observed in chronic methamphetamine abusers. Repeated methamphetamine abuse can also lead to addiction, a chronic, relapsing disease characterized by compulsive drug seeking and use, accompanied by chemical and molecular changes in the brain. Some of these changes persist long after methamphetamine abuse is stopped. Reversal of some of the changes, however, may be observed after sustained periods of abstinence, such as more than one year.\n\nTaking even small amounts of methamphetamine can result in many of the same physical effects as those of other stimulants, such as cocaine or amphetamines, including increased wakefulness, increased physical activity, decreased appetite, increased respiration, rapid heart rate, irregular heartbeat, increased blood pressure, and hyperthermia. Long-term methamphetamine abuse has many negative health consequences, including extreme weight loss, severe dental problems known as meth mouth, anxiety, confusion, insomnia, mood disturbances, and violent behavior. Chronic methamphetamine abusers can also display psychotic features, including paranoia, visual and auditory hallucinations, and delusions, such as the sensation of insects crawling under the skin.\n\nTransmission of HIV and hepatitis B and C can be consequences of methamphetamine abuse. The intoxicating effects of methamphetamine, regardless of how it is taken, can alter judgment and inhibition and can lead people to engage in unsafe behaviors, including risky sexual behavior. Among abusers who inject the drug, HIV/AIDS and other infectious diseases can be spread through contaminated needles, syringes, and other injection equipment used by more than one person. Methamphetamine abuse may also worsen the progression of HIV/AIDS and its consequences. Studies of methamphetamine abusers who are HIV-positive indicate that HIV causes greater neuronal injury and cognitive impairment for individuals in this group compared with HIV-positive people who do not use the drug."