Methamphetamine is a potent central nervous system (CNS) stimulant that is mainly used as a recreational drug and less and less commonly as a second-line treatment for attention deficit hyperactivity disorder and obesity. It is highly addictive, neurotoxic (it can damage dopamine and serotonin neurons in the brain) and it is the second-highest illicit drug used worldwide. As a stereoisomer it is available in two forms, d- and l-form, with the d- form being the most frequently used. Drug screening assays typically detect the presence of d-methamphetamine in whole blood, oral fluids, serum, plasma, and urine samples.