Metoclopramide is a drug that works by antagonizing or blocking D2 receptor signaling. Blocking of D2 receptor signaling in the brainstem can inhibit vomiting centers, thereby helping to treat nausea and vomiting as an anti-emetic. Metoclopramide also works to increase GI motility as a prokinetic, which is useful in the treatment of gastroparesis and acid reflux. One serious adverse effect of taking metoclopramide is a risk for causing Tardive dyskinesia and dystonic reactions.
Some of the other less important adverse effects are restlessness, drowsiness, fatigue, diarrhea and depression. Metoclopramide is contraindicated in the patients who have small bowel obstruction, schizophrenia or Parkinson disease, as D2 receptor antagonism or increases in GI motility can worsen these disorders.