synthetic drug used in the treatment of moderate to severe pain. It is an opioid analgesic, and thus its effects on the body resemble those of opium or morphine, one of opium's purified constituents. A common trade name for meperidine is Demerol.

The drug acts principally on the central nervous system (nervous system, human). It can be administered orally, in liquid or tablet form, or by intramuscular or subcutaneous injection. Its effects are felt within 15 minutes and last from 3 to 5 hours. Meperidine is used to relieve pain during childbirth, although it may slow the respiratory rate of both mother and infant. The drug also may be used as an aid in preoperative sedation and anesthesia. Side effects include drowsiness, lightheadedness, dryness of the mouth, weakness, and nausea. Meperidine is highly addictive; however, its side effects tend to be less severe than those of morphine, making it a preferable choice in many instances.