Chapter 33: Drugs Used for the Treatment of Bowel Disorders
A 23-year-old woman with a history of type 1 diabetes since age 6 presents with nausea and vomiting associated with gastroparesis and delayed gastric emptying. Which of the following medications would be the most suitable treatment of the nausea and vomiting in this patient?
Answer is b. Metoclopramide is a dopamine (DA) receptor antagonist that is commonly used to treat the symptoms of delayed gastric emptying. Another drug that might be used is cisapride although it is available only through a limited use program because of its incidence of serious cardiovascular toxicities. Erythromycin is also a possible alternative.
A 64-year-old woman is receiving ondansetron for the prophylactic treatment of emesis secondary to chemotherapy. Ondansetron’s main mechanism of action is antagonism of
a. central μ opioid receptors.
b. peripheral H2 receptors.
c. central dopamine receptors.
d. central 5-HT3 receptors.
e. peripheral muscarinic receptors.
Answer is d. Ondansetron is a central 5-HT3 receptor antagonist. Table 33-3 shows a general classification of anti-emetic drugs.
Table 33-3. General Classification of Anti-emetic Agents
|ANTI-EMETIC CLASS ||EXAMPLES ||TYPE OF VOMITING MOST EFFECTIVE AGAINST |
|5-HT3 receptor antagonistsa ||Ondansetron ||Cytotoxic drug induced emesis |
|Centrally acting dopamine receptor antagonists || |
|Cytotoxic drug induced emesis |
|Histamine H1 receptor antagonists ||Cyclizine ||Vestibular (motion sickness) |
|Muscarinic receptor antagonists ||Hyoscine (scopolamine) ||Motion sickness |
|Neurokinin receptor antagonists ||Aprepitant ||Cytotoxic drug induced emesis (delayed vomiting) |
|Cannabinoid receptor agonists ||Dronabinol ||Cytotoxic drug induced emesis |
A 35-year-old woman has severe irritable bowel syndrome characterized by frequent and profuse diarrhea. She is being treated with alosetron because she has not responded to other forms of antidiarrheal therapy. The physician treating this patient must diligently monitor for
b. congestive heart failure.