Demerol, also known as meperidine, is a strong medicine that doctors give to people who have serious pain. It works by affecting certain parts of the brain to make the pain less noticeable. People usually take it as a pill or get it through a needle. While it can help with pain, it can also cause side effects like feeling sleepy, dizzy, or sick to the stomach. It's important to take it exactly as the doctor says because it can be harmful if taken too much or for too long.
Pharmacokinetics:

Absorption: Meperidine is well absorbed from the gastrointestinal tract after oral administration.
Distribution: Widely distributed throughout the body, including crossing the blood-brain barrier.
Metabolism: Metabolized primarily in the liver to normeperidine, which is an active metabolite.
Excretion: Excreted by the kidneys. The elimination half-life of meperidine is approximately 2.5-4 hours, while normeperidine has a longer half-life.