Indications

• Gastric Bezoar
• Gastroesophageal Reflux Disease (GERD) (see Gastroesophageal Reflux Disease, Gastroesophageal Reflux Disease)
• Gastroparesis (see Gastroparesis, Gastroparesis)
• Hiccups (see Hiccups, Hiccups)
• Lactation Stimulant
• Migraines (see Migraines, Migraines)
• Nausea/Vomiting (see Nausea and Vomiting, Nausea and Vomiting)
• Tourette Syndrome (see Tourette Syndrome, Tourette Syndrome)
• Vascular Headaches

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Pharmacology

• Dopamine D2 Receptor Antagonist (see Dopamine Receptor Antagonists, Dopamine Receptor Antagonists): at low dose
  • Central Dopamine D2 Receptors: located in the central nervous system chemoreceptor trigger zone
  • Peripheral Dopamine D2 Receptors
• Mixed Serotonin 5-HT3 Receptor Antagonist and Serotonin 5-HT4 Receptor Agonist (see Serotonin 5-HT3 Receptor Antagonists, Serotonin 5-HT3 Receptor Antagonists): at high dose
• Enhances Acetylcholine Release and Stimulates Cholinergic Receptors on Gastric Smooth Muscle

Physiologic Effects

• Antiemetic Effect
  • Mediated by antagonism at dopamine D2 receptors in the chemoreceptor trigger zone of the central nervous system
  • May alse be mediated by antagonism at the 5-HT3 receptor when used at higher doses
• Gastroprokinetic Effect: may contribute to the antiemetic effect
  • Mediated by muscarinic activity, dopamine D2 receptor antagonist activity, and 5-HT4 receptor agonist activity
• Increased Lower Esophageal Sphincter Tone

Metabolism

• Renal: 85% of oral dose appears in the urine within 72 hrs (50% is present as free or conjugated metoclopramide)
• Half-Life: 5-6 hrs

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Administration

• PO: 5-10 mg q6hrs
  • Onset: 30-60 min
  • Duration: 1-2 hrs
• IV: 5-10 mg q6hrs
  • Onset: 1-3 min
  • Duration: 1-2 hrs

Dose Adjustment

• Hepatic: none
• Renal: decrease initial dose by 50% in patients with CrCl <40 mL/min

Use in Pregnancy (see Pregnancy, Pregnancy)

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Drug Interactions

• Monoamine Oxidase (MAO) Inhibitors (see Monoamine Oxidase Inhibitors, Monoamine Oxidase Inhibitors)
  • Metoclopramide Increases Catecholamines, Potentiating the Hypertensive Effects of MAO Inhibitors
• Serotonin Reuptake Inhibitors (see Selective Serotonin Reuptake Inhibitors, Selective Serotonin Reuptake Inhibitors and Serotonin-Norepinephrine Reuptake Inhibitors, Serotonin-Norepinephrine Reuptake Inhibitors)
  • Concomitant Use of Metoclopramide with Serotonin Reuptake Inhibitors May Increase Metoclopramide Levels and the Risk of Adverse Effects
  • Metoclopramide Possibly Increases the Risk of Serotonin Syndrome (see Serotonin Syndrome, Serotonin Syndrome)
• Sedatives
  • Metoclopramide Potentiates Effects of Other Sedatives
• Succinylcholine (see Succinylcholine, Succinylcholine)
  • Metoclopramide Inhibits Plasma Cholinesterase, Prolonging the Effect of Succinylcholine

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Adverse Effects

Cardiovascular Adverse Effects

• Atrioventricular Block
  • First Degree Atrioventricular Block (see First Degree Atrioventricular Block, First Degree Atrioventricular Block)
  • Second Degree Atrioventricular Block-Mobitz Type I (Wenckebach) (see Second Degree Atrioventricular Block-Mobitz Type I, Second Degree Atrioventricular Block-Mobitz Type I)
  • Second Degree Atrioventricular Block-Mobitz Type II (see Second Degree Atrioventricular Block-Mobitz Type II, Second Degree Atrioventricular Block-Mobitz Type II)
  • Third Degree Atrioventricular Block (see Third Degree Atrioventricular Block, Third Degree Atrioventricular Block)
• Congestive Heart Failure (CHF) (see Congestive Heart Failure, Congestive Heart Failure)
  • Physiology: due to increased aldosterone secretion, resulting in fluid retention
• Hypertension (see Hypertension, Hypertension)
• Hypotension (see Hypotension, Hypotension)
• Sinus Bradycardia (see Sinus Bradycardia, Sinus Bradycardia)

Dermatologic Adverse Effects

• Urticaria (see Urticaria, Urticaria)

Endocrine Adverse Effects

• Galactorrhea (see Galactorrhea, Galactorrhea): due to hyperprolactinemia
• Gynecomastia (see Gynecomastia, Gynecomastia)

Gastrointestinal Adverse Effects

• Diarrhea (se Diarrhea, Diarrhea)

Hematologic Adverse Effects

• Leukopenia/Neutropenia (see Leukopenia, Leukopenia and Neutropenia, Neutropenia)

Neurologic Adverse Effects

• Delirium/Confusion (see Delirium, Delirium)
• Depression (see Depression, Depression)
• Drowsiness/Lethargy/Obtundation (see Obtundation-Coma, Obtundation-Coma)
• Extrapyramidal Symptoms (see Extrapyramidal Symptoms, Extrapyramidal Symptoms)
  • Akathisia (see Akathisia, Akathisia): motor restlessness
  • Dystonia (see Dystonia, Dystonia): continuous spasms and muscle contractions
  • Tardive Dyskinesia (see Tardive Dyskinesia, Tardive Dyskinesia): irregular, jerky movements
  • Parkinsonism (see Parkinson’s Disease, Parkinsons Disease): cogwheel rigidity, bradykinesia, tremor, mask-like facies

Renal Adverse Effects

• Green Urine (see Urine Discoloration, Urine Discoloration)

Toxicologic Adverse Effects

• Methemoglobinemia (see Methemoglobinemia, Methemoglobinemia)
• Sulfhemoglobinemia (see Sulfhemoglobinemia, Sulfhemoglobinemia)

Other Adverse Effects

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References

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