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Drugs, Supplies and Delivery
Metoclopramide
Metoclopramide is a dopamine receptor antagonist and prokinetic agent used to treat nausea, vomiting, and gastrointestinal motility disorders. It is widely prescribed for conditions such as gastroparesis, chemotherapy-induced nausea, and migraine-associated vomiting. This article synthesizes information from the British National Formulary (BNF), Lippincott Textbook of Pharmacology, and Lange Basic & Clinical Pharmacology to provide a detailed overview of metoclopramide, including its mechanism, uses, dosing, side effects, precautions, and drug interactions.
Metoclopramide exerts its effects through two primary mechanisms:
- Dopamine D2 Receptor Antagonism:
- Blocks dopamine D2 receptors in the chemoreceptor trigger zone (CTZ) of the brain, preventing nausea and vomiting.
- Enhances gastric motility by blocking inhibitory dopamine receptors in the gastrointestinal (GI) tract (Lippincott, Lange).
- Prokinetic Effects:
- Stimulates acetylcholine release in the GI tract, increasing lower esophageal sphincter tone, accelerating gastric emptying, and improving intestinal motility (BNF).
- Nausea and Vomiting:
- Effective in chemotherapy-induced, postoperative, and migraine-associated nausea and vomiting (BNF).
- Gastroparesis:
- Improves symptoms of delayed gastric emptying, such as bloating and postprandial fullness (Lippincott).
- Gastroesophageal Reflux Disease (GERD):
- Used off-label for refractory GERD due to its prokinetic effects (Lange).
- Radiographic Procedures:
- Facilitates small bowel imaging by accelerating intestinal transit (BNF).
- Adults:
- Nausea/Vomiting: 10 mg orally/intravenously/intramuscularly every 6–8 hours (max 30 mg/day).
- Gastroparesis: 10 mg orally 30 minutes before meals and at bedtime (max 40 mg/day) (BNF).
- Chemotherapy-Induced Nausea: 1–2 mg/kg intravenously 30 minutes before chemotherapy (Lippincott).
- Children (≥1 year):
- 0.1–0.15 mg/kg/dose every 6–8 hours (max 0.5 mg/kg/day) (Lange).
Administration:
- Intravenous doses should be administered slowly over 1–2 minutes to reduce the risk of restlessness or dystonia.
- Avoid long-term use (>12 weeks) due to the risk of tardive dyskinesia (BNF).
- Common: Drowsiness, restlessness, diarrhea, and fatigue (Lippincott).
- Serious:
- Extrapyramidal Symptoms (EPS): Acute dystonia, akathisia, and Parkinsonism (especially in children and young adults).
- Tardive Dyskinesia: Irreversible involuntary movements with prolonged use.
- Neuroleptic Malignant Syndrome (NMS): Rare but life-threatening (Lange).
- Contraindications:
- Gastrointestinal obstruction, perforation, or hemorrhage.
- Pheochromocytoma (risk of hypertensive crisis) (BNF).
- Elderly Patients: Higher risk of EPS and tardive dyskinesia; avoid prolonged use (Lippincott).
- Pregnancy: Use only if benefits outweigh risks; crosses the placenta (Lange).
- Parkinson’s Disease: May exacerbate symptoms due to dopamine blockade (BNF).
- CNS Depressants (e.g., opioids, benzodiazepines): Enhanced sedation (Lippincott).
- Antipsychotics (e.g., haloperidol): Increased risk of EPS and NMS (Lange).
- Serotonergic Drugs (e.g., SSRIs): Risk of serotonin syndrome (BNF).
- Digoxin: Reduced absorption due to accelerated GI transit (Lippincott).
Metoclopramide is the generic name for this medication. It is marketed under brand names such as Reglan® and Maxolon®. Generic formulations are widely available in oral tablets, liquid suspensions, and injectable forms.
