They travel fastest to organs with a rich blood supply - the heart, the lungs, and the brain. Drugs that are inhaled, smoked, or injected directly into the bloodstream get into those organs the fastest. Because drugs travel throughout the body, they can affect different organs at the same time. For example, sniffed glue may simultaneously intoxicate the brain and damage liver cells. For example, nicotine combines with nerve cells to increase the rate of electrical conduction - this increases the heart rate and blood pressure.
Inhalants interact with brain cells to slow electrical conduction, which causes intoxication.
Drugs usually leave the body through the liver and the kidneys. Some, like inhalants can be eliminated by the lungs in the breath. Most drugs leave the body within days or hours after they have been taken. Nicotine, for example, is eliminated so rapidly that a person must smoke cigarettes continuously through the day to keep the nicotine level high enough for its effects to be felt. In contrast, THC, the active ingredient in marijuana leaves the body so slowly that it can be detected for at least several days after it was smoked.