“Smack” is the “common” name for
Heroin or di-acetyl-morphine is about two times more potent than morphine in injectable form. Apart from the parenteral mode of administration,
heroin can also be smoked or ‘chased’ ( chasing the dragon), often in an impure form (called ‘ smack’ or ‘ brown sugar’ in India). 
Heroin is more addicting than morphine and can cause dependence even after a short period of exposure.
Heroin
Cocaine
Opium
None