Ecstasy. Tablet of the illegal drug ecstasy (3, 4 methylenedioxymethamphetamine or MDMA). Ecstasy induces feelings of elation, energy and well being. Possible side effects include dehydration, involuntary muscle movements and psychological difficulties. There is some evidence that long term use may cause brain damage. The smiley symbol on the tablet was an emblem adopted by the 1980s acid house dance music culture that popularised the use of ecstasy as a recreational drug.