Meperidine hydrochloride is a synthetic opioid prescribed for the relief of moderate to severe pain. It is also known by other names such as pethidine, Demerol, and meperidine HCl. While its mechanism of action is similar to that of other opioids, its chemical structure sets it apart, and therefore different names. Other synonyms for meperidine hydrochloride include isonipecaine, lidol, amidonarcotic, and dolantin. Some of these names are used in different parts of the world or in specific medical settings. Regardless of the name used, it is essential to use meperidine hydrochloride responsibly and only under the guidance of a medical professional.