Metoclopramide is a "prokinetic" drug that stimulates the muscles of the gastrointestinal tract including the muscles of the lower esophageal sphincter, stomach, and small intestine by interacting with receptors for acetylcholine and dopamine on gastrointestinal muscles and nerves.

The lower esophageal sphincter, located between the esophagus and the stomach, normally prevents reflux of acid and other contents in the stomach from backing up into the esophagus. In patients with gastroesophageal reflux disease (GERD), a weakened lower esophageal sphincter allows reflux of stomach acid into the esophagus, causing heartburn and damage to the esophagus (esophagitis). Metoclopramide decreases the reflux of stomach acid by strengthening the muscle of the lower esophageal sphincter. Metoclopramide also stimulates the muscles of the stomach and thereby hastens emptying of solid and liquid meals from the stomach and into the intestines.

In some patients, particularly those with diabetes, damage to nerves in the stomach can interfere with function of the muscles and cause delayed emptying of the stomach, resulting in nausea, vomiting, a sense of abdominal fullness and distention, and heartburn (diabetic gastroparesis). Metoclopramide can be effective in relieving the symptoms related to diabetic gastroparesis by stimulating more rapid emptying of the stomach as well as decreasing the reflux of stomach acid into the esophagus. Dopamine receptors on nerves in the brain are important in producing nausea. Metoclopramide interacts with the dopamine receptors in the brain and can be effective in treating nausea. The FDA approved metoclopramide in June 1985.

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Metoclopramide is generally well-tolerated when used in low doses for brief periods. Neurological side effects increase with higher doses and longer periods of treatment. Common side effects of metoclopramide are:

• drowsiness,
• restlessness,
• fatigue,
• anxiety,
• insomnia,
• depression,
• and sedation.

Other important side effects of metoclopramide include serious neurological symptoms that mimic Parkinson's disease such as:

• involuntary muscle movements,
• facial grimacing, and
• dystonic reactions resembling tetanus.

Fortunately, these more serious side effects are infrequent and usually - though not always - disappear when metoclopramide is discontinued. Patients with Parkinson's disease can experience worsening of symptoms with metoclopramide. Metoclopramide may impair the mental and/or physical abilities to drive or operate machinery.

The usual dose of metoclopramide for treating GERD is 10-15 mg four times daily, 30 minutes before each meal.

Gastroparesis is treated with 10 mg administered orally four times daily, 30 minutes before each meal and at bedtime.

Since metoclopramide accelerates emptying of the stomach, it can increase or decrease absorption and effects of other drugs that are absorbed in the small intestine. For example, the effects of alcohol, diazepam (Valium) and cyclosporine can be accelerated when used together with metoclopramide. Conversely, metoclopramide may decrease the concentrations in blood of digoxin (Lanoxin) and cimetidine (Tagamet). Metoclopramide should not be used in patients taking MAO inhibitors for example, isocarboxazid (Marplan), phenelzine (Nardil), tranylcypromine (Parnate), selegiline (Eldepryl), and procarbazine (Matulane), because of the risk of serious adverse effects due to excess release of neurotransmitters. Concurrent administration of anticholinergic drugs can decrease the effectiveness of metoclopramide.

The safety of metoclopramide in pregnancy has not been established.

Metoclopramide is excreted in human breast milk. Nursing mothers should avoid metoclopramide during pregnancy.

What preparations of metoclopramide are available?

• Tablets: 5 and 10 mg.
• Syrup: 5 mg/5 ml.
• Injection: 5 mg/ml

How should I keep metoclopramide stored?

Tablets and syrup should be stored between 15 C - 30 C (59 F - 86 F). Injectable metoclopramide should be stored at room temperature 20 C - 25 C (68 F - 77 F).