Материал: 2016_Kaplan_USMLE_Step_1_Lecture_Notes_Pharmacology

Section VI λ Drugs for Inflammatory and Related Disorders

17.Answer: B. Several drugs, including ketoconazole and fluoroquinolones, require an acidic environment in the gastrointestinal tract for effective absorption into the systemic circulation. Drugs used in treatment of gastrointestinal

ulcers such as proton pump inhibitors (lansoprazole) commonly increase gastric pH, leading to the ↓ absorption of such drugs and, consequently, a ↓ in their effects.

18.Answer: C. Cromolyn is a mast-cell stabilizer used in asthma (especially anti- gen-induced) and in food allergies. Inhibition of degranulation with decreased release of histamine and eicosanoids contributes to its antiinflammatory effectiveness in asthma, where it is used for prophylaxis. Methylxanthines, such as

theophylline, exert bronchodilating effects via their inhibition of phosphodiesterases and their antagonism of adenosine receptors. Steroids used in asthma ↓ bronchial hyperactivity by several mechanisms, including inhibition of interleukin synthesis. COX 2 inhibitors have no established role in asthma management.

19.Answer: A. Latanoprost is a prostanglandin F2α analog that is used in glaucoma to lower intraocular pressure. Ergonovine causes smooth muscle contraction (both uterine and vascular) and is used for control of postpartum hemor-

rhage. Atropine has the potential to raise intraocular pressure and precipitate

glaucoma. Neither a β2 agonist (terbutaline) nor opioids (morphine) is useful in glaucoma.

20.Answer: C. Allopurinol is a uricosuric drug used in chronic gout that prevents formation of uric acid from purines by acting as a suicide substrate of xanthine oxidase. The drug is commonly used in patients undergoing treatment of cancer to slow down formation of uric acid derived from purines released by the cytotoxic action of drugs or radiation. The metabolism of 6-mercaptopurine (6-MP), a substrate for xanthine oxidase, is also inhibited by allopurinol, necessitating a major dose reduction to avoid its toxic effects.

21.Answer: B. Docusate is a stool-softening laxative that facilitates mixing of oil and water via its surfactant properties. Drugs that have muscarinic blocking effects, such as scopolamine and the antihistamines diphenhydramine and promethazine, tend to cause constipation by decreasing gastrointestinal motility. Loperamide is an opioid derivative, with no analgesic activity, used in the treatment of diarrheal states.

22.Answer: C. Over-the-counter (OTC) sleep aids invariably contain sedating antihistamines such as diphenhydramine. Sometimes called sedative-autonom- ics, overdoses of such drugs are dangerous, especially in small children. They usually have muscarinic-blocking (atropine-like) effects causing hyperthermia, and they lower the seizure threshold, leading to convulsions. Chlorpromazine is very similar in its pharmacology but is not available OTC and would not be appropriate as a sleeping aid because of its autonomic side effects. Temazepam, a benzodiazepine, is used as a sleeping pill but requires a prescription and raises the seizure threshold. Meperidine is an opioid-analgesic that can cause seizures in OD, but it is not used as a sleeping aid or available OTC. Caffeine is a CNS stimulant.

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Chapter 9 λ Inflammatory Disorder Drug List and Practice Questions

23.Answer: E. Ethanol has mixed effects on liver metabolism of drugs. Acutely, it can act as an enzyme inhibitor, but chronic use may lead to enzyme induction. Acetaminophen is metabolized mainly via conjugation reactions, but a minor pathway involving P-450 (probably the CYP2E1 isoform) results in formation of small amounts of the reactive metabolite, which is (normally) rapidly inactivated by GSH. The chronic ingestion of more than average amounts of ethanol induces the formation of the P-450 isozyme that converts acetaminophen to its reactive metabolite. Thus, more-than-normal amounts of N-acetyl- benzoquinoneimine would be formed in an overdose situation, resulting in enhanced hepatotoxicity.

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SECTION VII

Drugs Used in

Blood Disorders