NIDA: Why injecting is more addictive than oral use.

The shorter the amount of time between administration and a drug's effects, the more addictive it is. This has been known for decades. It's one of the reasons why smoking nicotine is so addictive — smoking as a route of administration goes directly from the lungs to the brain. This applies to crack cocaine as well. Insufflation (through the nose) is also very rapid. Injection into a vein is not as fast as inhalation, as the drug must first go through the bloodstream to get to the brain, but it is very fast. Slowest of all is oral administration, especially "extended release" therapeutic formulations. But a new clinical trial sponsored by the National Institute on Drug Abuse (NIDA) and the National Institute on Alcohol Abuse and Alcoholism (NIAAA) suggests that a "salience network" in the brain is responsible for the difference between intravenous and oral response to a drug. [ABSTRACT FROM AUTHOR]