Metoclopramide

Introduction Overview

Generic Name

metoclopramide

Brand Name

Metozolv ODT, Reglan, Gimoti

Dosage Form

oral tablet, orally disintegrating tablet (ODT), oral solution, injection (intramuscular and intravenous)

Drug Class

GI stimulants, Miscellaneous antiemetics

Pharmacokinetics

Absorption:
Metoclopramide is well absorbed after oral administration with peak plasma concentrations typically reached within 1 to 2 hours. The bioavailability ranges between 80-100%, indicating minimal first-pass metabolism. Absorption may be slightly delayed with food but not significantly reduced. The orally disintegrating tablet formulation allows for rapid dissolution and absorption through the oral mucosa, potentially leading to faster onset of action. Parenteral administration (IM or IV) bypasses the gastrointestinal tract, providing immediate bioavailability.

Distribution:
Metoclopramide is widely distributed throughout body tissues, including the gastrointestinal tract, crossing the blood-brain barrier to a limited extent, which accounts for its central nervous system effects. The volume of distribution ranges from approximately 3.5 L/kg, indicating extensive tissue uptake. It demonstrates moderate plasma protein binding, primarily to albumin. Distribution into central nervous system tissues underlies its dopaminergic antagonism effects. It also crosses the placenta and is excreted into breast milk.

Metabolism:
Metoclopramide undergoes partial hepatic metabolism, primarily via conjugation pathways such as glucuronidation and sulfation. Cytochrome P450 involvement appears minimal, reducing potential for CYP-mediated interactions. Metabolism results in inactive metabolites. The degree of hepatic metabolism varies, but it constitutes less than 20% of the administered dose. Impaired liver function can decrease metabolism, potentially necessitating dose adjustment.

Elimination:
Excretion is primarily renal, with approximately 85% of an administered dose recovered unchanged in the urine within 72 hours. The elimination half-life in healthy adults ranges from 5 to 6 hours. Renal impairment significantly prolongs half-life and increases systemic exposure, requiring careful dosage adjustments. Metoclopramide is efficiently cleared by the kidneys, and its clearance correlates strongly with creatinine clearance. Minor elimination via feces occurs. The drug's pharmacokinetics remain linear over therapeutic dose ranges.

Dosage Forms

Available Dosage Forms:
- Oral tablets: 5 mg and 10 mg tablets
- Orally disintegrating tablets (ODT): 5 mg and 10 mg
- Oral solution: Concentrations available include 5 mg/5 mL
- Injection: Sterile solution for IM or IV administration, typically 5 mg/1 mL vials

Dosages for Adults and Adolescents:
- Gastroesophageal reflux disease (GERD): 10 to 15 mg orally up to 4 times daily, 30 minutes before meals and at bedtime; treatment duration should not exceed 12 weeks
- Diabetic gastroparesis (oral): 10 mg orally, 4 times daily, 30 minutes before meals and at bedtime, for 2 to 8 weeks; (parenteral): 10 mg IM or IV up to 4 times daily for up to 10 days
- Postoperative nausea and vomiting: 10 to 20 mg IM near end of surgery
- Chemotherapy-induced nausea and vomiting (CINV): IV infusion of 1 to 2 mg/kg/dose 30 minutes before chemotherapy, repeated based on symptoms
- Small intestine intubation facilitation: 10 mg IV slow injection over 1 to 2 minutes if tube has not passed pylorus
- Migraine (off-label): 10 to 20 mg IV once (usually combined with analgesics)

Specific Patient Populations:
- Pediatric: Not FDA approved for GERD; studied doses include 0.4 to 0.8 mg/kg/day divided into 4 doses orally/IM/IV for reflux; 0.1 mg/kg IV for small intestine intubation in children under 6 years; dose adjustments required based on indication and age
- Renal impairment: Dosage reduction recommended due to decreased clearance
- Hepatic impairment: Caution advised; dose adjustment may be necessary
- Geriatric patients: Increased risk of extrapyramidal symptoms, use lowest effective dose, limit duration to 12 weeks or less

Clinical Guidelines:
Oral formulations are typically used for chronic conditions or outpatient settings, while parenteral injections are reserved for acute indications such as severe gastroparesis and prevention of nausea/vomiting with chemotherapy or surgery. Duration of therapy should be limited to minimize risk of movement disorders. The ODT formulation is preferred for patients with difficulty swallowing. The oral solution allows dose flexibility in pediatrics and geriatric patients. Injection should be diluted appropriately for doses >10 mg.

Mechanism Of Action

Metoclopramide acts primarily as a dopamine D2 receptor antagonist at both central (chemoreceptor trigger zone) and peripheral sites within the gastrointestinal tract, exerting antiemetic and prokinetic effects. By blocking dopamine receptors in the chemoreceptor trigger zone of the medulla, metoclopramide suppresses nausea and vomiting induced by chemotherapy, surgery, or toxins. This antagonism decreases dopaminergic inhibition of cholinergic neurons, facilitating enhanced acetylcholine release.

In the gastrointestinal tract, metoclopramide enhances gastric motility and accelerates gastric emptying without increasing gastric secretions. It achieves this by sensitizing tissues to acetylcholine, resulting in increased amplitude and tone of gastric contractions and improved coordination of gastric and small intestinal peristalsis. It also relaxes the pyloric sphincter and the duodenal bulb, allowing more rapid transit of stomach contents to the small intestine. These effects help alleviate symptoms such as gastroparesis-associated fullness, nausea, and reflux.

At higher doses, metoclopramide exhibits weak antagonism of serotonin 5-HT3 receptors and agonism at serotonin 5-HT4 receptors, which may contribute to its prokinetic and antiemetic properties. However, this activity is less prominent compared to specific 5-HT3 antagonists or 5-HT4 agonists.

Clinically, the dopamine antagonism responsible for antiemetic effects can also lead to central nervous system side effects, including extrapyramidal symptoms and tardive dyskinesia, especially with prolonged use or high doses. Research has demonstrated that metoclopramide's efficacy is superior in conditions involving delayed gastric emptying and dopamine-mediated nausea pathways. Its mechanism contrasts with other antiemetics such as ondansetron, a selective 5-HT3 antagonist, highlighting differing receptor targets influencing therapeutic use.

Pharmacological Actions

Dopamine D2 receptor antagonist providing antiemetic effects
Enhancement of upper gastrointestinal motility and acceleration of gastric emptying
Sensitization of gastrointestinal smooth muscle to acetylcholine increasing contractility
Relaxation of pyloric sphincter facilitating gastric content movement
Weak 5-HT3 receptor antagonism contributing to antiemetic action
5-HT4 receptor agonism promoting prokinetic activity
Reduction of nausea and vomiting symptoms in chemotherapy, postoperative states, and gastroparesis
Improvement of gastroesophageal reflux symptoms by promoting gastric emptying
Central nervous system dopamine receptor blockade underlying extrapyramidal side effects
Facilitation of small intestine intubation through enhanced gastric motility
Potential modulation of chemoreceptor trigger zone signaling to prevent vomiting reflex
Minimal anticholinergic effects compared to other prokinetics
No significant effect on gastric acid secretion
Prokinetic effects helpful in treating diabetic gastroparesis
Rapid onset of action with parenteral administration

Therapeutic Or Clinical Uses

Treatment of gastroesophageal reflux disease (GERD) in patients unresponsive to other treatments
Management of diabetic gastroparesis to improve gastric emptying and relieve associated symptoms
Prevention and treatment of nausea and vomiting induced by chemotherapy
Prevention and treatment of postoperative nausea and vomiting
Facilitation of gastric emptying prior to radiographic examinations of the stomach and small intestine
Enhancement of gastric motility to assist in small intestine intubation procedures
Symptomatic relief of heartburn caused by delayed gastric emptying
Off-label use in management of migraine-associated nausea when used with analgesics
Use as an antiemetic in various medical procedures involving the gastrointestinal tract
Short-term treatment (up to 12 weeks) for upper gastrointestinal motility disorders
Adjunct to facilitate lactation augmentation due to its effect on prolactin secretion
Treatment of gastroparesis symptoms secondary to systemic diseases like diabetes
Use in hospitalized patients with severe nausea/vomiting requiring parenteral therapy
Supportive treatment to improve quality of life in chronic gastroparesis
Management of delayed gastric emptying post-surgery or in critical illness

Side Or Adverse Effects

Extrapyramidal symptoms including tremors, dystonia, and akathisia, especially with high doses or prolonged use
Tardive dyskinesia, a potentially irreversible movement disorder with long-term therapy
Drowsiness and somnolence due to central nervous system dopamine antagonism
Fatigue and malaise
Headache and dizziness
Confusion and cognitive disturbances, particularly in elderly patients
Insomnia and sleep disturbances
Nausea and vomiting paradoxically may occur
Neuroleptic malignant syndrome, a rare but life-threatening condition
Depression, anxiety, and mood changes including suicidal ideation
Hypotension and hypertension occasionally reported
Diarrhea or abdominal cramps
Allergic reactions such as rash, urticaria, and rarely angioedema
Jaundice and signs of hepatic dysfunction in rare cases
Withdrawal symptoms including headache, dizziness, and nervousness upon abrupt discontinuation

Precautions

Avoid metoclopramide in patients with a history of tardive dyskinesia or other extrapyramidal disorders
Limit duration of therapy to no more than 12 weeks to minimize risk of irreversible movement disorders
Use with caution in patients with kidney or liver impairment; dose adjustment may be necessary
Careful monitoring in elderly patients due to increased susceptibility to CNS side effects
Avoid concurrent use with other central nervous system depressants unless supervised
Inform patients about potential for central nervous system effects including drowsiness and mood changes
Use cautiously in patients with diabetes due to increased risk of adverse movement disorders
Monitor for symptoms of neuroleptic malignant syndrome especially in early therapy
Avoid use in patients with known pheochromocytoma to prevent hypertensive crisis
Use cautiously in patients with congestive heart failure and hypertension
Avoid in patients with gastrointestinal obstruction, perforation, or bleeding
Assess mental health status before and during treatment due to risk of depression and suicidal thoughts
Advise against alcohol consumption during therapy to prevent potentiation of side effects
Monitor for extrapyramidal symptoms and instruct patients to report any involuntary movements immediately
Not approved for use in children under 18; pediatric use requires careful consideration and dosing

Warnings

Risk of tardive dyskinesia increases with duration and dosage; potential irreversibility of this movement disorder
Contraindicated in patients with history of tardive dyskinesia or extrapyramidal symptoms induced by metoclopramide or similar drugs
Not to be used in gastrointestinal obstruction, perforation, or hemorrhage
Do not exceed recommended dosage or duration beyond 12 weeks to avoid serious neurologic adverse effects
Careful use required in patients with epilepsy or seizure disorders as metoclopramide may lower the seizure threshold
Possible increased risk of neuroleptic malignant syndrome characterized by muscle rigidity, fever, and altered mental status
Associated with depression, suicidal ideation, and other psychiatric symptoms requiring prompt medical attention
Risk of severe allergic reactions including anaphylaxis
Avoid use in patients with pheochromocytoma due to risk of hypertensive crisis
Use during late pregnancy may harm the fetus; weigh benefits versus risks carefully
Not recommended during breastfeeding due to potential for adverse reactions in the infant
Increased risk of adverse movement disorders in diabetic patients and older adult women
Warning about concomitant use with CNS depressants that may enhance sedation
Sudden discontinuation may lead to withdrawal effects such as headache and nervousness
Patients should stop drug and seek urgent medical care if signs of severe neurological or psychiatric effects appear

Contraindication

Known hypersensitivity to metoclopramide or any component of the formulation
History of tardive dyskinesia or other medication-induced extrapyramidal symptoms
Gastrointestinal obstruction, perforation, or gastrointestinal hemorrhage
Pheochromocytoma due to risk of hypertensive crisis
Epilepsy or other seizure disorders without proper control
Use of metoclopramide with concomitant drugs exhibiting similar dopamine antagonism resulting in cumulative risk
Past severe adverse reaction or hypersensitivity to phenylalanine-containing formulations (for ODT or oral liquids)
Patients with a history of metoclopramide-induced movement disorders
Use in pediatric patients under 18 for most indications due to lack of established safety and efficacy
Known central nervous system depression states that may be exacerbated by metoclopramide
Pregnancy during late trimesters due to potential fetal harm
Breastfeeding unless benefits outweigh risks and close monitoring is possible
Co-administration with drugs contraindicated due to pharmacodynamic or pharmacokinetic interactions

Drug Interactions

Additive CNS depressant effects when used with opioid analgesics, benzodiazepines, barbiturates, or alcohol
Antagonism of levodopa and dopamine agonists reducing therapeutic efficacy in Parkinson’s disease
Increased risk of extrapyramidal symptoms and tardive dyskinesia when combined with antipsychotics such as haloperidol, risperidone, and chlorpromazine
Potential increased plasma concentrations of cyclosporine when administered concurrently
May reduce absorption of tetracycline by increasing gastrointestinal motility
Concomitant use with digoxin may alter digoxin pharmacokinetics, requiring monitoring
Interaction with MAO inhibitors potentially leading to hypertensive crisis or severe side effects
Anticholinergic agents may antagonize prokinetic effects of metoclopramide
Blood pressure medications may have altered effects when co-administered
Bronchodilators like ipratropium or tiotropium may have diminished efficacy due to opposing effects
Concurrent use with acetaminophen generally safe but should be monitored for symptom overlap
Possible increased sedation or respiratory depression with muscle relaxants or seizure medications
Glycopyrrolate and other urinary antispasmodics may reduce metoclopramide’s gastrointestinal effects
Caution with drugs metabolized hepatically as metoclopramide may affect enzyme activity
Extensive list of psychiatric medications including clozapine and prochlorperazine interact increasing risk of neurologic side effects

Preparations Of The Drug

Oral tablets: Typically 5 mg and 10 mg strengths for systemic use
Orally disintegrating tablets (ODT): 5 mg and 10 mg, designed for rapid dissolution in the oral cavity
Oral solution: Metered liquid suspension, commonly 5 mg/5 mL concentration, suited for dose flexibility
Injectable solution for Intramuscular or Intravenous use: Sterile 5 mg/mL vials
Metoclopramide injection diluted with normal saline or other parenteral solutions for doses exceeding 10 mg
Blister packs utilized for ODT tablets to maintain stability and prevent damage prior to administration
Packaging designed to protect from moisture and heat; storage at room temperature recommended
Pre-filled syringes and single-dose vials available for ease of use in clinical settings
Compounded formulations are occasionally prepared for pediatric or precise dosing requirements
Commercial preparations labeled to indicate presence of phenylalanine, important for patients with PKU
Different brands such as Reglan, Metozolv ODT, and Gimoti offer varying formulations and administration routes
Patient information leaflets provided to ensure proper usage and awareness of side effects
Storage conditions emphasize tight closure and protection from ambient humidity
Refrigeration not typically required but should be avoided to prevent precipitation
Dosage delivery devices like oral syringes are provided with liquid formulations for accurate dosing