metoclopramide
Meaning of metoclopramide: Benefit and hazard flow from one action, the blocking of dopamine, in the gut in one case and the brain in the other.
Definition of metoclopramide
Metoclopramide is a medication that speeds the movement of food out of the stomach and through the upper intestine while also blocking a signal in the brain that triggers nausea. That combination gives it two roles at once: it treats sluggish stomach emptying and it treats nausea and vomiting arising from a range of causes.
How does one drug do two jobs?
Both effects come from blocking dopamine receptors, in two different places. In the wall of the digestive system, dopamine normally restrains the release of the messenger that makes gut muscle contract. Removing that restraint strengthens contractions of the stomach and upper small intestine and tightens the valve at the lower end of the esophagus, so the stomach empties faster and reflux is reduced. The colon is largely unaffected. In the brain, the same blockade acts on a small region that monitors the bloodstream for substances signaling poisoning and triggers vomiting when it finds them, which is what makes the drug an antiemetic.
What is it used for?
| Situation | Which action is doing the work |
|---|---|
| Gastroparesis, a stomach that empties too slowly | The effect on gut muscle |
| Nausea and vomiting after surgery or with chemotherapy | The effect in the brain |
| Nausea accompanying migraine | Both, since gut movement also stalls during an attack |
| Passing a feeding tube beyond the stomach | The effect on gut muscle |
Why is treatment kept short?
The drug crosses into the brain, and dopamine is also the messenger of the pathways controlling movement. Blocking it there can produce sudden muscle spasms of the neck, jaw or eyes, most often soon after starting and more commonly in younger people; an inner restlessness that makes sitting still difficult; and a slowing and stiffness resembling Parkinson disease. The effect of greatest concern appears after prolonged exposure: tardive dyskinesia, involuntary repetitive movements of the face, tongue and limbs that may persist after the drug is stopped. Regulators require a warning about this and set a limit on how long a course should run. Blocking dopamine also raises the hormone prolactin, which can cause breast tenderness or milk production.
Also known as
Used in a sentence
Metoclopramide was given to help control nausea related to the patient's chemotherapy regimen.
Good to know
Prolonged use of metoclopramide carries a risk of tardive dyskinesia, an involuntary movement disorder that can persist after the drug is stopped, which is why courses are limited rather than continued indefinitely.