Metoclopramide

Metoclopramide is a dopamine D₂-receptor antagonist used to treat nausea, vomiting, and delayed gastric emptying. It also promotes movement through the upper digestive tract.

Dopamine D₂ receptor: A G-protein-coupled receptor activated by dopamine and blocked by drugs including metoclopramide. Blocking these receptors in the chemoreceptor trigger zone reduces signals that provoke vomiting.
Gastroparesis: A disorder in which the stomach empties more slowly than normal without a mechanical blockage. Metoclopramide is used to relieve symptoms and improve emptying in selected cases.
Tardive dyskinesia: A movement disorder involving repetitive, involuntary movements that can persist after exposure to certain medicines. Long-term metoclopramide exposure can cause this potentially persistent adverse effect.
Ondansetron: An antiemetic that blocks serotonin 5-HT₃ receptors in peripheral and central emetic pathways. Unlike metoclopramide, it generally does not increase gastric motility or cause dopamine-blockade movement disorders.
Serotonin 5-HT₄ receptor: A serotonin receptor whose activation can enhance neurotransmitter release and gastrointestinal motility. Metoclopramide’s 5-HT₄ agonism contributes to its prokinetic effect.
Chemotherapy-induced nausea and vomiting: Nausea and vomiting caused by cancer treatments that activate peripheral or central emetic pathways. Metoclopramide can be used as an antiemetic, though other medicines are often preferred for highly emetogenic regimens.
Acute dystonia: A sudden episode of sustained involuntary muscle contractions that can produce abnormal postures or movements. This extrapyramidal reaction can occur soon after starting or increasing metoclopramide.
Domperidone: A dopamine D₂-receptor antagonist used as an antiemetic and prokinetic, with limited penetration into the brain. Its lower central nervous system penetration distinguishes its movement-related risks from metoclopramide’s.
Chemoreceptor trigger zone: A brainstem region that detects blood-borne emetic substances and can activate vomiting circuits. D₂-receptor blockade here helps explain metoclopramide’s action against nausea and vomiting.
Migraine: A neurological disorder marked by recurrent attacks of headache and associated symptoms such as nausea. Metoclopramide may treat migraine-associated nausea and can support absorption of oral pain medicines.

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