Reglan - Side Effects and Withdrawal Symptoms
Reglan, one of the trade names for the medical drug metoclopramide, is classified as a dopamine antagonist. In order to understand the side effects of this drug, it is helpful to learn how the brain and nervous system work together in order to control bodily functions and the role of dopamine.
The Body's Internet
Think of your brain as a server and your nervous system as the Internet. In this case, your "Internet terminals" are the individual cells. The brain issues instructions to these cells through your nervous system. Just as sending data over the Internet requires electrical energy, brain signals require something to convey instructions along the neural pathways. The transmitter in this case is a neurochemical called dopamine.
In order to receive these instructions, it is necessary for them to be translated into a form that the cells can understand. While your personal computer has a modem in order to translate electrical data into information your browser can read, your cells have dopamine receptors that receive and translate instructions from the brain. There are several different kinds of dopamine and dopamine receptors, each of which deal with specific bodily and/or neural functions. Medications that are dopamine antagonists block these signals for specific dopamine receptors and have the potential to cause tardive dyskinesia.
Antipsychotics and Other Medications
Dopamine antagonists were originally developed in the 1950s and '60s in order to treat psychiatric patients. These medications targeted a specific dopamine receptor known as D2, which is responsible for the control of certain muscle operations and neural feedback mechanisms.
Metoclopramide was initially developed for this purpose, but was found to be less effective than many other antipsychotic drugs currently in use at the time. However, it was effective in controlling certain gastrointestinal disorders by blocking dopamine receptors of the digestive system. Symptoms that could be controlled included heartburn, acid reflux and gastroparesis, which is partial or complete paralysis of the stomach.
Problems Arise with Metoclopramide (Reglan)
Metoclopramide became popular in the late 1990s after its predecessor, Cisapride, was found to cause serious side effects. Unfortunately for many patients who had already begun to take metoclopramide, a study published in 2004 found the medication could cause a movement disorder known as tardive dyskinesia.
These symptoms were more likely to occur in older female patients who had taken the drug for an extended period of time, but others taking the drug were at risk as well. This ultimately led to action by the Food and Drug Administration, requiring a "black box" warning on all packages of Reglan.
Other Side Effects
Although tardive dyskinesia is one of the more visible side effects of Reglan, there are several others that can result from the withdrawal of the medication. Symptoms associated with Parkinson's disease can occur after someone has been using or stopped using Reglan. In addition, the use of Reglan has been known to trigger seizures or convulsions. Patients with epilepsy may be especially susceptible to these side effects.
Some patients have reported undefined feelings of anxiety, restlessness, agitation and sleep difficulties. In extreme cases, patients have been known to become suicidal. More obvious side effects can include dryness of the mouth and gastrointestinal disorders that include constipation and diarrhea. Other patients may experience loss of bladder control.
Reglan can also act as a diuretic, increasing the production of urine. In rare cases, patients may suffer from fever, sore throat, chills and symptoms associated with liver disease, including nausea, vomiting, dark urine and jaundice (yellowing of the eyes and skin). Dizziness and changes in vision can occur in a number of patients.
Sexual Dysfunction and Heart Problems
Excessive breast tenderness and menstrual changes have been noticed in some female patients. Males may experience gynecomastia (development of male "breasts") and impotence. Extended use of Reglan is also associated with a potentially life-threatening heart condition called tachycardia, which causes an abnormally fast heart rate. Reglan can aggravate hypertension or cause hypotension (low blood pressure) as well.
Neuroleptic Malignant Syndrome
Reglan patients suffering from fever, muscular stiffness, movement difficulties or delirium should call a physician right away, as these may be symptoms of neuroleptic malignant syndrome, a condition associated with dysfunction of the D2 dopamine receptor. It is potentially life-threatening if not treated quickly.
- HealthCentral. "Reglan Oral Side Effects." http://www.healthcentral.com/acid-reflux/find-drug-50680-73.html?ic=4031
- Mihara, K. et. al. "Relationship Between Functional Dopamine D2 and D3 Receptors Gene Polymorphisms and Neuroleptic Malignant Syndrome". American Journal of Medical Genetics Part B, vol. 117B, no. 1 (February 2003).
- RxList. "Reglan: Side Effects." http://www.rxlist.com/reglan-drug.htm
- Shaffer, Douglas et. al. "Tardive Dyskinesia and Metoclopramide Use: Effects of Cisapride Market Withdrawal." Journal of the American Pharmacists Association vol. 44 no. 6 (2004).