A 55-year-old female is receiving chemotherapy for metastatic carcinoma. She threatens to stop her treatment because of severe nausea and vomiting. The oncologist plans to use prochlorperazine to reduce the nausea and vomiting associated with chemotherapeutic agents. What is the mechanism of action of prochlorperazine?
Correct Answer: B
Explanation B: A variety of drugs have been found to be of some value in the prevention and treatment of vomiting, especially cancer chemotherapy-induced vomiting. With the exception of thioridazine, most of the neuroleptic drugs have antiemetic effects that are mediated by blocking D2 dopaminergic receptors of the chemoreceptor trigger zone of the medulla. Phenothiazines, such as prochlorperazine, were the first drugs shown to be effective antiemetic agents and act by blocking dopamine receptors. They are effective against low to moderately emetogenic chemotherapeutic agents (for example, fluorouracil and doxorubicin). Although increasing the dose improves antiemetic activity, side effects, including hypotension and restlessness, are dose limiting. Other adverse reactions include extrapyramidal symptom and sedation. A: Serotonin 5-HT3 antagonist is incorrect. The specific antagonists of the 5-HT3 receptor, ondansetron and granisetron, selectively block 5-HT3 receptors in the periphery and in the brain (chemoreceptor trigger zone). C: Cannabinoids related is incorrect. Cannabinoids are marijuana derivatives including dronabinol and nabilone and are effective against moderately emetogenic chemotherapy. However, they are seldom first-line antiemetics because of serious side effects. D: Blockage of prostaglandins is incorrect. Dexamethasone and methylprednisolone used alone are effective against mildly to moderately emetogenic chemotherapy. Their antiemetic mechanism is not known, but it may involve blockade of prostaglandins. E: H2 receptor antagonist is incorrect. Antagonists of histamine H2 receptor block the action of histamine at all H2 receptors; their chief clinical use is as inhibitors of gastric acid secretion.
Question 67
Before use, which of the following products should be used to clean surfaces of a laminar flow hood?
Correct Answer: B
Explanation Before each use, 70% isopropyl alcohol should be used to clean surfaces of a laminar flow hood.
Question 68
Which of the following is true regarding extent of absorption of drugs?
Correct Answer: A
Explanation It is not necessary that all the drugs get completely absorbed after oral administration. Most of them are incompletely absorbed. The extent of absorption varies from 5 to less than 100 % with oral ingestion of drugs. Drugs which are too hydrophilic like atenolol are incompletely absorbed because the drug cannot cross the lipid membrane due to high hydrophilic nature of the drug. Similarly, drugs which are too lipophilic like acyclovir are not soluble enough to cross the water layer adjacent to the cell. P-glycoprotein is an efflux transporter which is present in the enterocytes and it inhibits absorption of drug. It is also known as export transporter or reverse transporter. It has many drugs as its substrate. Grape juice in fact inhibits P-glycoprotein in the intestine thereby decreasing the efflux of drug from the cells by P-glycoprotein. Thus ingestion of grape juice may lead to significantly increased absorption of the drug.
Question 69
What vitamin should the a patient receive to avoid Wernicke- Korsakoff syndrome?
Correct Answer: A
Thiamine should be administered to prevent Wernicke's encephalopathy. Reference: http://www.uptodate.com/contents/management-of-moderate-and-severe-alcohol-withdrawal-syndromes
Question 70
Which of the following NSAIDs is an Enolic acid derivative?
Correct Answer: B
The following NSAIDs belong to the propionic acid derivatives group - Ibuprofen - Ketoprofen - Naproxen - Fenoprofen - Flurbiprofen - Oxaprozin whereas piroxicam belongs to the class of Enolic acid derivative which also includes other agents like meloxicam and Nabumetone. They are non-selective COX inhibitors and act by preventing the production of certain prostaglandins.
