Methamphetamine (from N-methyl-alpha-methylphenethylamine) is a neurotoxin and potent psychostimulant of the phenethylamine and amphetamine classes that is used as a recreational drug and, rarely, to treat attention deficit hyperactivity disorder (ADHD) and obesity. Recreationally, methamphetamine is used to increase sexual desire, lift the mood, and increase energy, allowing some users to engage in sexual activity continuously for several days straight.