blank">Methamphetamine (methylamphetamine or desoxyephedrine), popularly shortened to meth and also nicknamed "ice" and Tina, is a psychostimulant and sympathomimetic drug. The dextrorotatory isomer dextromethamphetamine can be prescribed to treat attention-deficit hyperactivity disorder, though unmethylated amphetamine is more commonly prescribed. _Narcolepsy and obesity can also be treated by the aforementioned isomer under the brand name Desoxyn. It is considered a second line of treatment, used when amphetamine and methylphenidate cause the patient too many side effects. It is only recommended for short term use (~6 weeks) in obesity patients because it is thought that the anorectic effects of the drug are short lived and produce tolerance quickly, whereas the effects on CNS stimulation are much less susceptable to tolerance. It is also used illegally for weight loss and to maintain alertness, focus, motivation, and mental clarity for extended periods of time, and for recreational purposes.

Methamphetamine enters the brain and triggers a cascading release of norepinephrine, dopamine and serotonin. To a lesser extent methamphetamine acts as a dopaminergic and adrenergic reuptake inhibitor and in high concentrations as a monamine oxidase inhibitor (MAOI). Since it stimulates the mesolimbic reward pathway, causing euphoria and excitement, it is prone to abuse and addiction. Users may become obsessed or perform repetitive tasks such as cleaning, hand-washing, or assembling and disassembling objects. Withdrawal is characterized by excessive sleeping, eating and depression-like symptoms, often accompanied by anxiety and drug-craving. Users of methamphetamine often take one or more benzodiazepines as a means of "coming down".