Originally developed to treat nausea during pregnancy, metoclopramide has become helpful in the treatment of nausea at large, acid reflux and vomiting. It is also effective in treating gastroparesis, a chronic disorder in which stomach muscles take longer than normal to push food into the small intestine. Like most medications, however, metoclopramide may cause adverse reactions. Its effects on weight are rare and vary with the dosage, as well as your age and medical condition.
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Mechanism of Action
Metaclopramide mainly works by blocking dopamine receptors, but it also has the ability to block serotonin receptors in your central nervous system. Dopamine and serotonin are neurotransmitters, or chemical messengers, that your brain uses to regulate key functions, including your mood, energy and appetite. Serotonin generally increases your feeling of fullness, while dopamine tends to increase your appetite when you smell food. As Wright State University School of Medicine physician Randy Sansone remarks, both neurotransmitters have been implicated in weight gain. However, the net effects of metaclopramide vary with its dosage, as well as the number of receptors you have.
Although the frequency of adverse reactions is not always defined, the scientific literature contains very few reports of weight-related side effects of metoclopramide. What's more, metoclopramide's effects on weight are not consistent. Rather, they seem to vary with the patient's age, physical and psychological health. According to the Mosby's 2010 Drug Reference, more common side effects of metoclopramide include the following: fatigue, suicide ideation, sleeplessness, heart rate disturbances, low blood pressure, seizures, dry mouth, vomiting, nausea, diarrhea, decreased libido and rash.(Reference 1)
Effects on Infant Weight
It's not uncommon for doctors to combine medications with other interventions during weight restoration. As far back as the early 1980s, physicians were already using metoclopramide to induce weight gain in preterm and and low-weight full-term infants. However, Dr. Sansone argues that medications alone rarely have a significant effect on weight gain. A 2005 issue of "Evidence-Based Nursing" also reports that metoclopramide may reduce acid reflux symptoms in otherwise healthy 1- to 24-month old infants. Acid reflux often causes poor feeding in infants and can lead to poor growth.
Effects on Adult Weight
Metoclopramide can have weight-related effects in anorexic adults and cancer patients. Characteristic of anorexia are reduced appetite and/or intense dislike for food, associated with weight loss. Although most people view it as a psychological disorder, anorexia may also be linked with chronic illness in cancer patients. Studies reported in a 2005 issue of the "Journal of Clinical Oncology" suggest that, while metaclopramide significantly improves nausea symptoms in cancer patients, it is less helpful for weight gain. By contrast, it can lead to significant weight gain in other anorexics, according to Dr. Sansone. Sudden weight gain is more rare in otherwise healthy adults taking metoclopramide.
Effects on Elderly Weight
In a 2003 issue of the "Journal of the American Geriatrics Society," physicians report cases of failure to thrive in elderly patients undergoing metoclopramide therapy. According to their report, even at therapeutic dosages, metoclopramide can both lead to severe weight loss and compromise the ability of elderly patients to carry out their daily activities. Note, however, that these effects have been observed in patients above the age of 65 with preexisting medical conditions. It's not clear whether metoclopramide would similarly affect otherwise healthy elderly individuals.