Reglan Side Effects

Because Reglan can interfere with the brain chemical dopamine, people who take the drug are at risk of developing tardive dyskinesia (TD) and neuroleptic malignant syndrome (NMS), two of the drug’s most serious side effects. The medication’s more common side effects are generally less severe and include fatigue and restlessness.

Last Modified: September 7, 2023
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Reglan (metoclopramide) is prescribed for gastrointestinal disorders. The most common side effects of the drug are relatively minor and include restlessness, drowsiness, fatigue and a general lack of energy.

More than 10% of patients who took the drug in clinical trials experienced one or more of these side effects, according to the medication’s prescribing information. How long the side effects lasted and their severity depended on the dosage and how long patients took the drug.

Other minor side effects that occurred less often included:
  • Breast enlargement or discharge
  • Decreased sexual ability
  • Diarrhea
  • Fluid retention
  • Frequent urination or incontinence
  • Headache, confusion or dizziness
  • Impaired ability to drive or operate machinery
  • Insomnia, anxiety or agitation
  • Missed periods
  • Nausea or vomiting

The U.S. Food and Drug Administration requires Reglan’s label to include a black box warning — the agency’s most serious warning — for tardive dyskinesia (TD). The sometimes irreversible and disfiguring movement disorder can occur with long-term, high dose use of the drug.

The prescribing information also warns of a risk of neuroleptic malignant syndrome (NMS). The potentially deadly condition affects muscles, organs and other body parts and can dangerously alter a patient’s mental state.

Both conditions may be reversed if a patient stops taking the drug. But if not treated immediately, the side effects can result in permanent disfigurement, disability or even death.

Tardive Dyskinesia Risk Serious But Rare

The active ingredient in Reglan, metoclopramide, was found to cause tardive dyskinesia in some patients, especially those taking the drug for longer than 12 weeks.

The risk of developing TD — and the likelihood that the condition will become irreversible — increases the longer a person takes the drug and the more Reglan a person takes.

The black box warning advises patients to “avoid treatment with Reglan for longer than 12 weeks because of the risk of developing TD with longer-term use.”

It’s important to note that the drug itself may hide the signs of TD. People who use the drug should call their doctor right away if they experience uncontrollable movements involving their tongue, mouth or face. These could include puckering of the mouth, frowning or scowling, and lip smacking or chewing. Some patients may suffer involuntary blinking and eye movements or shaking of their arms and legs.

“Avoid treatment with Reglan for longer than 12 weeks because of the increased risk of developing TD with longer-term use.”

There is no known treatment for tardive dyskinesia, and symptoms may not go away after discontinuing metoclopramide. However, in some patients, symptoms may lessen or resolve after the drug is stopped.

Elderly patients, especially elderly women, may be at an increased risk of developing TD with Reglan. Due to the risk of TD, patients should avoid using the drug for longer than 12 weeks and elderly patients should consider a reduced dosage.

Reglan should not be used in patients with a history of TD or patients receiving other drugs that are likely to cause the condition.

The risk of TD is serious, but it is also rare. In 2010 — less than a year after the FDA required the black box warning for TD — a study in the journal Alimentary Pharmacology and Therapeutics looked at the risk of developing the condition from the drug. It found that less than 1% of patients taking high doses of the drug long-term may be at risk of developing TD. National guidelines previously suggested an estimated risk of 1% to 10%.

In January 2017, manufacturers of generic forms of Reglan tentatively agreed to settle thousands of lawsuits that claimed the drugs caused tardive dyskinesia and other nervous system disorders.

According to a September 2022 article in StatPearls, metoclopramide increases the risk of postpartum depression and tardive dyskinesia in breastfeeding women.

Neuroleptic Malignant Syndrome and Other Serious Side Effects

In very rare cases, metoclopramide may cause a possibly fatal condition called neuroleptic malignant syndrome. NMS can occur within hours of starting the drug and must be treated in a hospital.

Symptoms of NMS include fever, hyperthermia, and altered consciousness. People who develop NMS after taking Reglan may also experience muscle rigidity, which is the inability of the muscles to relax normally, and signs of autonomic instability, such as irregular pulse or heartbeat, change in blood pressure and unusual sweating.

Patients taking other drugs associated with NMS, including all antipsychotic medications, should avoid taking Reglan.

The drug’s label also carries warnings of several others potentially serious side effects. Many of them affect the central nervous system.

Other serious side effects:
  • Blood disorders
  • Cardiovascular disorders including congestive heart failure
  • Depression
  • Drug-induced Parkinson’s
  • Hallucinations
  • High blood pressure (hypertension)
  • Hypersensitivity disorders including breathing spasms, rashes or hives
  • Physical or mental impairment
  • Problems with vision
  • Suicide or suicidal thoughts

Please seek the advice of a medical professional before making health care decisions.