Recently the FDA required the manufacturers of the drug metoclopramide, more commonly know as Reglan, to place a black box warning on its label. A black box warning is the strongest warning that the FDA can require.
Metoclopramide increases muscle contractions in the upper digestive tract, which speeds up the rate at which the stomach empties into the intestines. It is used short-term to treat heartburn caused by gastrophageal reflux, and also used to treat slow gastric emptying in people with diabetes, a condition called diabetic gastroparesis.
However, in recent studies, it has been shown that people taking metoclopramide can develop a serious condition called Tardive Dyskinesia.
Tardive Dyskinesia is a condition in which a person develops involuntary movements of their muscles which could include lip smacking, tongue thrusting, eye blinking and bulging, head jerking, facial grimacing, puckering and pursing of the lips, and involuntary movements of the fingers.
Long-term users of the drug, and elderly patients, especially women are at an increased risk of developing Tardive Dyskinesia. There is no known cure for Tardive Dyskinesia and even after discontinuing the drug, symptoms may still persist.