Metoclopramide

What Is Metoclopramide?

Metoclopramide is a dopamine D2 receptor antagonist used primarily to treat nausea and vomiting, and to accelerate gastric emptying in conditions where stomach motility is impaired. It acts centrally in the chemoreceptor trigger zone of the brain to block the dopamine signals that trigger the vomiting reflex, and also works peripherally in the gastrointestinal tract to promote coordinated muscular contractions that move food through the stomach and into the small intestine.

This dual central and peripheral action distinguishes metoclopramide from purely peripheral antiemetics, making it useful for a range of conditions including chemotherapy-induced nausea, post-operative sickness, gastroparesis, and the nausea associated with migraine attacks. It is also used in the management of gastro-oesophageal reflux disease (GORD), particularly where delayed gastric emptying is a contributing factor.

Duration Restrictions

A critically important aspect of metoclopramide use is that it must not be taken for more than five consecutive days. This restriction was introduced following regulatory review due to the risk of tardive dyskinesia, a potentially irreversible movement disorder characterised by repetitive, involuntary movements, particularly of the face, tongue, and limbs. The risk is highest with prolonged use and in young women, elderly patients, and those taking high doses.

Available Formulations

Metoclopramide is available in several formulations to suit different clinical situations. Oral tablets (10 mg) are used for outpatient management of nausea and GORD. Syrup is available for patients who have difficulty swallowing tablets. Injectable forms (intravenous and intramuscular) are used in hospital settings for acute vomiting or pre-operative preparation. All formulations carry the same five-day maximum duration restriction.

How to Take Metoclopramide

Metoclopramide tablets are taken orally, usually 30 minutes before meals and at bedtime. The standard dose of 10 mg may be taken up to three times daily, ideally before mealtimes to maximise the prokinetic benefit. For the management of nausea associated with migraine, it is typically taken at the onset of the migraine attack, before or alongside pain relief, as it also helps improve the absorption of co-administered analgesics by promoting gastric motility.

It is essential to follow the prescribed regimen carefully and not to exceed the maximum daily dose of 30 mg or the maximum treatment duration of five consecutive days. If nausea or vomiting continues beyond five days, a medical review is required to identify and address the underlying cause rather than continuing medication.

Special Considerations

Younger patients and elderly individuals are particularly susceptible to extrapyramidal side effects, including dystonic reactions such as involuntary muscle spasms of the face, tongue, and neck. If any abnormal movements or muscle stiffness occur, the medication should be stopped immediately and medical advice sought. Patients should also be aware that metoclopramide can cause drowsiness and may affect their ability to drive or operate machinery.

The standard adult dose of metoclopramide is 10 mg taken up to three times daily, ideally 30 minutes before meals. The maximum daily dose is 30 mg (or 0.5 mg per kg bodyweight, whichever is lower). Treatment must not exceed five consecutive days due to the risk of tardive dyskinesia.

For patients with renal impairment, dose reduction is recommended: the dose should be halved in moderate to severe renal impairment (eGFR below 40 mL/min). Elderly patients and those weighing under 60 kg should also start at the lower end of the dose range (5 mg three times daily) to minimise the risk of extrapyramidal reactions. Metoclopramide is not recommended for children under one year of age and should be used with great caution in older children.

Common Side Effects

Most people tolerate metoclopramide well for short courses, but some side effects may occur even at standard doses.

• Drowsiness or fatigue
• Restlessness or agitation (akathisia)
• Diarrhoea
• Headache
• Dry mouth
• Depressed mood

Serious Side Effects

Serious reactions, while less common, require immediate medical attention.

• Tardive dyskinesia: Repetitive, involuntary movements of the face, tongue, lips, or limbs, potentially irreversible with prolonged use. Stop medication immediately and seek medical advice.
• Acute dystonic reactions: Sudden involuntary muscle spasms of the neck, jaw, eyes, or trunk, more common in young adults and women. Treated with anticholinergic medication such as procyclidine.
• Neuroleptic malignant syndrome: A rare but life-threatening reaction causing fever, severe muscle rigidity, altered consciousness, and autonomic instability.
• Hyperprolactinaemia: Elevated prolactin levels may cause breast enlargement, galactorrhoea (milk production), or menstrual irregularities with prolonged use.
• Cardiovascular effects: QT prolongation has been reported; caution is required in patients with cardiac arrhythmias.

Extrapyramidal Reactions and Tardive Dyskinesia

Metoclopramide carries a significant risk of movement disorders that must be understood before starting treatment. Acute dystonic reactions, including involuntary muscle spasms and facial grimacing, can occur after even a single dose, particularly in young women, elderly patients, and those on higher doses. These are usually reversible with prompt treatment. However, tardive dyskinesia, a chronic and potentially irreversible movement disorder, can develop with prolonged use and is the primary reason the five-day treatment limit was imposed.

Any patient who develops abnormal movements, tremor, rigidity, or unusual facial or limb activity during treatment should stop metoclopramide immediately and seek urgent medical review. The prescriber should be informed so that alternative antiemetic options can be considered.

Other Important Precautions

Metoclopramide increases gut motility and must not be used when gastrointestinal motility stimulation is hazardous, such as in cases of gastrointestinal obstruction, perforation, or shortly after gastrointestinal surgery. It should be avoided in patients with phaeochromocytoma, as dopamine blockade in this setting can trigger a dangerous hypertensive crisis. Caution is also required in patients with Parkinson's disease, where it may worsen motor symptoms, and in those with epilepsy, as it may lower the seizure threshold.

Metoclopramide must not be used in patients with any of the following:

• Known hypersensitivity to metoclopramide or any excipient
• Gastrointestinal obstruction, perforation, or haemorrhage
• Phaeochromocytoma (risk of hypertensive crisis)
• History of tardive dyskinesia or metoclopramide-induced movement disorders
• Epilepsy (increased frequency and severity of seizures)
• Parkinson's disease (may worsen symptoms)
• Prolactin-dependent tumours, including certain breast cancers
• Concomitant use with other dopamine antagonists (additive extrapyramidal risk)
• Infants under one year of age