Metoclopramid

Metoclopramide, sometimes spelled metoclopramid, is a medication used as an antiemetic and a prokinetic agent. It is employed to prevent nausea and vomiting from surgery or chemotherapy and to treat gastroparesis and some cases of gastroesophageal reflux disease. It is available in oral, intravenous, and intramuscular forms, and also as a suppository in some markets.

The drug acts in two ways. Its antiemetic effect mainly results from blockade of dopamine D2 receptors in the chemoreceptor trigger zone of the brain. Its prokinetic effect arises from partial agonism at serotonin 5-HT4 receptors in the gastrointestinal tract, which enhances gastric emptying and increases lower esophageal sphincter tone.

Pharmacokinetics and administration: Metoclopramide is well absorbed when taken by mouth and can be given IV or IM for rapid effect. Oral onset is typically within 30 to 60 minutes; intravenous administration is faster. The elimination half-life is about 5 to 6 hours. It is metabolized in the liver and excreted mainly in the urine.

Dosing and duration: Doses vary by indication. For adults with nausea, typical oral dosing is 10 mg up to three or four times daily (maximum about 40 mg per day). For gastroparesis, 10 mg four times daily before meals and at bedtime. Intravenous or intramuscular dosing is used for rapid antiemetic effect and is given at the clinician’s discretion. Treatment should be limited to short courses, generally not exceeding 12 weeks, due to the risk of movement disorders.

Adverse effects and precautions: Common adverse effects include drowsiness, fatigue, and restlessness. Dopamine blockade can cause extrapyramidal symptoms such as dystonia or akathisia; tardive dyskinesia can occur with long-term use. Metoclopramide can increase prolactin, causing galactorrhea or menstrual disturbances. It can worsen Parkinsonian symptoms and may lower seizure threshold. Cautions include GI obstruction, perforation, hemorrhage, and hypersensitivity; use with caution in elderly patients and those with epilepsy or Parkinson disease. It can interact with other CNS depressants and alcohol.