metoclopramide hydrochloride

The hydrochloride salt of the substituted benzamide metoclopramide, a para-aminobenzoic acid (PABA) derivative that is structurally related to procainamide, with gastroprokinetic and antiemetic activities. Metoclopramide binds to dopamine 2 (D2) receptors in the peripheral nervous system (PNS), antagonizing dopamine-mediated relaxation of gastrointestinal smooth muscle and promoting gastroprokinesis; the pyloric sphincter and the duodenal bulb are relaxed, peristalsis of the duodenum and jejunum increase, and gastric emptying and intestinal transit accelerate. This agent may also increase the resting tone of the lower esophagus sphincter (LES), preventing acid reflux. In the central nervous system (CNS), metoclopramide antagonizes D2 dopamine receptors in the chemoreceptive trigger zone (CTZ) of the medulla, thereby preventing nausea and vomiting.