However meth is ingested, it works quickly, giving the user an intense rush that some call a "flash". A feeling of euphoria that can last for several hours follows this rush. Other effects include increased energy and activity, decreased appetite, increased alertness, and a sense of well being. One reason for the popularity of meth is because these effects can last for up to 12 hours. There are reports that the effects experienced depend on the form of meth and the method of ingestion.
Methamphetamines work on the crystal meth drug central nervous system by activating certain neurotransmitters in the brain. Much higher levels of methamphetamine get into the brain and stay there for a longer period of time than what is experienced with amphetamine or cocaine, for example.