Due to its desirable effects and short duration, although ketamine does not create a physical dependence, it is more like a psychologically addictive substance. It is sure that the users have not physical cravings for ketamine. But it is also sure that, over time, the same ketamine users will develop a tolerance for the drug [...]

Heroin is the most rapidly acting drug of the opiates. Heroin is processed from morphine, a naturally occurring substance extracted from the seed pod of certain varieties of poppy plants. It is typically sold as a white or brownish powder or as the black sticky substance known on the streets as “black tar heroin.”
Because heroin [...]