In psychology, a rush is an acute transcendent state of euphoria. Psychoactive drugs which enhance dopaminergic neurotransmission in the central nervous system (CNS) are commonly capable of such an event.
These drugs include opiates and opioids, such as heroin and morphine, and psychostimulants, such as methamphetamine and cocaine. Studies have shown that the subjective pleasure of drug use (the reinforcing component of addiction) is proportional to the rate at which the blood level of the drug increases. Intravenous injection is the fastest route of administration, causing blood concentrations to rise the most quickly, followed by smoking, suppository (anal or vaginal insertion), insufflation (snorting), and ingestion (swallowing). 
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