Tardive Dyskinesia Introduction & Overview
Tardive dyskinesia is a condition that may develop in patients who use metoclopramide, a drug sold under brand names such as Reglan in the United States. When a patient has been taking certain prescription drugs over a long period of time, often in high dosages, involuntary, repetitive tic-like movements can result, primarily in the facial muscles or (less commonly) the limbs, fingers and toes. The hips and torso may also be affected.
Dyskinesia refers to the involuntary nature of muscular movements or the difficulty in performing voluntary muscular movement. Tardive means a condition has the tendency to appear late. Symptoms of tardive dyskinesia can develop and persist long after use of the medication causing the disorder has been discontinued. Tardive dyskinesia can appear similar to other types of disorders, most notably Tourette's syndrome.
History of Tardive Dyskinesia
Tardive dyskinesia was first named and classified in 1964. By the early 1960s, symptoms associated with tardive dyskinesia were apparent in approximately 30 percent of psychiatric patients treated with antipsychotic medications, linking the development of the condition to these drugs. The development of tardive dyskinesia is commonly linked to metoclopramide use. The drug metoclopramide (sold today under the brand name Reglan, among others) was developed in Europe in the mid-1960s and became available for use in 1982. In early 2009, the Food and Drug Administration issued a warning about metoclopramide, informing the public of research that suggests the use of metoclopramide is the most common cause of drug-induced movement disorders. A 2004 study found that older women treated with metoclopramide were at an increased risk for developing symptoms of tardive dyskinesia, additionally, men, infants and children are also commonly affected by metoclopramide-induced tardive dyskinesia..
Reglan & Tardive Dyskinesia
The development of tardive dyskinesia has often occurred in patients who have been treated for digestive and gastrointestinal disorders with medications such as metoclopramide (Deglan, Maxolon or Reglan). Metoclopramide medications may also cause the development of additional side effects including bowel obstruction, a condition also linked to the use of Accutane, a popular acne medication that may increase the risk of inflammatory bowel disease (IBD).
Though the use of metoclopramide medications can increase the likelihood of developing certain side effects, other factors may further increase the risk of various adverse reactions. In the case of tardive dyskinesia, risk factors appear to be age (certain older patients are more likely to develop tardive dyskinesia), gender (the condition is more common in females), mental retardation, a history of substance abuse and a traumatic head injury. According to an article published in the Journal of the American Medical Association, 31 percent of all tardive dyskinesia patients are over 55 years of age and have been taking medications for three months or longer. Tardive dyskinesia is also caused by the side effects of certain psychoactive drugs, including "dopamine antagonists" (drugs that block dopamine receptors, used to treat disorders of the nervous or circulatory system).
Dopamine & Tardive Dyskinesia
Research indicates that tardive dyskinesia results from damage to the systems that use and process dopamine. Dopamine is a biochemical substance produced in numerous areas of the brain. It functions as a neurotransmitter, working with the brain to regulate movement and emotion within the body.
Dopamine is significant when it comes to pleasurable sensations. When dopamine receptors are blocked, the dopamine remains in the synapse (where nerve impulses are transmitted and received) for a longer period of time. This creates a sense of "false euphoria," which is why some narcotics are so addictive. The fact that dopamine remains in the synapses for an extended period may also hold clues to what causes the onset of tardive dyskinesia in certain patients. When neurons can no longer hold dopamine, Parkinson's disease may result.
Metoclopramide is a dopamine receptor antagonist and inhibits the delivery of electro-chemical messages from the brain to various parts of the body. The drug has been implicated in the development of several movement disorders, including tardive dyskinesia.
Tardive Dyskinesia Treatment
The best treatment for tardive dyskinesia appears to be prevention, either by lowering the dosage of a medication known to cause this condition or switching the patient to a different drug. Tetrabenzine, a medication that reduces levels of dopamine, has been of some use in treating tardive dyskinesia symptoms. Some kinds of "anti-Parkinsonian" drugs such as Miraplex appear to offer some benefit as well.