Plenty to go around. This table shows a very brief, but interesting history of methylphenidate abuse.
Interestingly enough, while Methamphetamine and Ritalin are very hot commodities here in London, there are no national numbers to compare against.
As it quickly grows in popularity, is increasingly easy to find on the street, and with prices ranging from only $5-$15 per pill; Methylphenidate is an easily affordable prescription drug when compared to the high prices of prescription opiates on the street. Many intravenous drug users I have spoken with will interchangeably use crystal methamphetamine and Ritalin, as they find the high to be very similar, and often perceive Methylphenidate to be the cleaner safer version.
That however, is not necessarily the case.
"A review of 60 studies suggests that the reinforcing or subjective effects of methylphenidate (in 80% of these studies) functions similarly to d-amphetamine or cocaine (i.e., as a reinforcer, in drug discrimination substitution, and subjective effects such as producing a "high" or "rush"), and that there is definite abuse potential. Tolerance develops and characteristic stimulant withdrawal symptoms have been reported including fatigue or exhaustion, depression, unpleasant and vivid dreams, insomnia or hypersomnia, increased appetite, psychomotor retardation or agitation, or irritability. Similar effects may by expected with all repeated scripting stimulants".
Snorting or insuffilating methylphenidate has its consequences as well.
"The delicate epithelial tissues that line the nasal cavities and air passages may be damaged by direct contact with drugs. Ritalin tablets contain the hydrochloride salt of methylphenidate and yield dilute hydrochloric acid when they come into contact with moisture. While this is not a problem in the stomach (hydrochloric acid is one of the digestive acids used in the stomach), in the nasal passages the acid can 'burn' the delicate nasal tissues, resulting in open sores, nose bleeds, and possibly deterioration of the nasal cartilage".