This Office of National Drug Control Policy fact sheet gives an overview of methamphetamine trends in the United States. "Methamphetamine is a highly addictive central nervous system stimulant that can be injected, snorted, smoked, or ingested orally. Methamphetamine users feel a short yet intense 'rush' when the drug is initially administered. The immediate effects of methamphetamine include increased activity and decreased appetite. The drug has limited medical uses for the treatment of narcolepsy, attention deficit disorders, and obesity; however it is seldom prescribed by doctors."
White House, Office of National Drug Control Policy: http://www.whitehousedrugpolicy.gov/