MEPERIDINE HYDROCHLORIDE IS A NARCOTIC ANALGESIC WITH MULTIPLE ACTIONS QUALITATIVELY SIMILAR TO THOSE OF MORPHINE; THE MOST PROMINENT OF THESE INVOLVE THE CENTRAL NERVOUS SYSTEM AND ORGANS COMPOSED OF SMOOTH MUSCLE. THE PRINCIPAL ACTIONS OF THERAPEUTIC VALUE ARE ANALGESIA AND SEDATION. THERE IS SOME EVIDENCE WHICH SUGGESTS THAT MEPERIDINE MAY PRODUCE LESS SMOOTH MUSCLE SPASM, CONSTIPATION, AND DEPRESSION OF THE COUGH REFLEX THAN EQUIANALGESIC DOSES OF MORPHINE. THE ONSET OF ACTION IS SLIGHTLY MORE RAPID THAN WITH MORPHINE, AND THE DURATION OF ACTION IS SLIGHTLY SHORTER. MEPERIDINE IS SIGNIFICANTLY LESS EFFECTIVE BY THE ORAL THAN BY THE PARENTERAL ROUTE