Demerol,meperidine, is an older narcotic, used mainly through IV or IM use. It has much less effect when taken orally. It is a great med when given IM, or IV, but it hangs around in the body and tissues, so it tends to build up over time, and most docs will not use it now, since it has the cumulative affect. The biggest problem is when taken orally, it does not provide near the same relief as when given through IV access or as an injection, (IM)/. IT used to be the most used drug for post op pain. I am surprised to hear somebody has prescribed it. Hope it works for you.