métoclopramide

Metoclopramide, sometimes written métoclopramide in some regions, is a medication with antiemetic and prokinetic properties. It acts as a dopamine D2 receptor antagonist and also has a serotonin-mediated prokinetic effect, via 5-HT4 receptor agonism, which increases upper gastrointestinal motility. It crosses the blood–brain barrier, contributing to central antiemetic effects but also to extrapyramidal side effects.

Medical uses: It is used to prevent and treat nausea and vomiting due to postoperative conditions, chemotherapy, and radiotherapy. It is also used to treat gastroparesis and symptomatic gastroesophageal reflux with delayed gastric emptying. In some settings it is given as an adjunct for acute migraine with nausea.

Mechanism: In the CNS, D2 receptor antagonism in the chemoreceptor trigger zone reduces emesis. In the gut, 5-HT4 agonism enhances acetylcholine release, accelerating gastric emptying.

Safety and adverse effects: Common adverse effects include drowsiness, fatigue, and malaise. Extrapyramidal symptoms (acute dystonias, parkinsonian effects) and tardive dyskinesia can occur, particularly with long-term use. Hyperprolactinemia may cause galactorrhea, gynecomastia, or menstrual changes. Metoclopramide should be used with caution in patients with Parkinson's disease or a history of movement disorders; it is contraindicated in those with hypersensitivity to the drug or in the setting of GI obstruction, perforation, or hemorrhage. Rarely, seizures can occur. Pregnancy category B; it is excreted in breast milk and should be used during pregnancy only if clearly needed.

Pharmacokinetics and dosing: Metoclopramide is available orally and by injection. Oral onset is about 30–60 minutes; intravenous or intramuscular onset is rapid. It is hepatically metabolized and primarily excreted in urine; half-life ranges around 4–8 hours in adults.