metoclopramide

Metoclopramide is a medication used as an antiemetic and a prokinetic agent. It is commonly available in oral, intramuscular, and intravenous forms. It enhances gastrointestinal motility and also reduces nausea and vomiting.

Mechanism of action and effects on the GI tract: Metoclopramide acts as a dopamine D2 receptor antagonist in the chemoreceptor trigger zone, which contributes to its antiemetic effect. In the stomach, it increases lower esophageal sphincter tone and stimulates coordinated gastric and upper small intestinal peristalsis, thereby accelerating gastric emptying. It has little effect on intestinal transit beyond the upper GI tract.

Medical uses: It is used to prevent and treat nausea and vomiting associated with chemotherapy, anesthesia, and radiation therapy, as well as postoperative periods. It is also employed for management of symptoms of gastroesophageal reflux disease in patients who have not responded to other measures, and as a prokinetic agent in diabetic gastroparesis. Some adults may receive it for short-term relief of acute migraine‑associated nausea.

Dosing and safety considerations: Typical antiemetic dosing is 10 mg every 6 to 8 hours as needed, with a maximum daily dose generally around 80 mg. For gastroparesis, dosing is commonly 10 mg four times daily before meals and at bedtime for up to several weeks. Contraindications include mechanical GI obstruction, perforation, and GI hemorrhage; caution is advised in patients with seizure disorders or Parkinson’s disease. Long-term use or high doses carry a risk of extrapyramidal symptoms and tardive dyskinesia; it may cause drowsiness, fatigue, or galactorrhea. It should be used with caution in pregnancy (category considerations vary by region) and is excreted in breast milk.

Interactions and pharmacokinetics: Metoclopramide is absorbed orally and crosses the blood–brain barrier. It is metabolized in the liver and excreted by the kidneys. It can interact with agents that depress the central nervous system, anticholinergics, and levodopa. Dose adjustments may be needed in hepatic or renal impairment.