We have two patients. One requires suppression of emesis caused by an anticancer drug that causes a high incidence and severity of vomiting (highly emetogenic drug). Another patient has severe diabetic gastroparesis and gastroesophageal reflux, which requires relief. Which one drug would be suitable for both indications (assuming no specific contraindications)? (LQ)
a. Metoclopramide has clinically useful antiemetic and prokinetic actions and would be suitable for either of the patients described in the question.
b. The antiemetic effect arises from blockade of dopamine (and, probably, serotonin) receptors in the brain’s chemoreceptor trigger zone (CTZ). The drug is indicated for not only chemotherapy-induced nausea and vomiting, but also that which may occur with radiation therapy, postoperatively, or in response to opioid analgesics or emetogenic toxins.
c. The enhanced gastric and upper intestinal motility probably reflects an enhancement of the expected effects of ACh on muscarinic receptors found on longitudinal smooth muscle in the GI tract.
d. Metoclopramide raises the lower esophageal sphincter tone and relaxes the pyloric sphincter, which hastens gastric emptying.
e. This helps explain its beneficial effects in both gastroparesis and GERD. Importantly, the drug should not be given along with atropine because of its cholinergic properties.