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336, The answer is e, (Katzung.. pp 280-281.) Sumatriptan is closely related to serotonin (5-1 IT) in structure, and it is believed that the drug is effective in the treatment of acute migraine headaches by virtue of its selective agonistic activity at 5-1 ITlh receptors. These receptors, present on cerebral and meningeal arteries, mediate vasoconstriction induced by 5-1 IT. Ln addition, 5-1 IT m receptors are found on presynaptic nerve terminals and function to inhibit the release of neuropeptides and other neurotransmitters. It has been suggested that the pain of migraine headaches is caused by vasodilation of intracranial blood vessels and stimulation of trigemino-vascular axons, which cause pain and release vasoactive neuropeptides to produce neurogenic inflammation and edema. Sumatriptan acts to reduce vasodilation and the release of neurotransmitters and, therefore, reduces the pain that is associated with migraine headaches. Other antimigraine drugs (e.g., ergotamine and dihydroergofamine) also exhibit high affinities for the 5-HT1D-receptor site.

337, The answer is a, (Katzurig, p 267.) 11, receptors appear to be linked to phospholipase C; activation of these receptors results in an increase in the intracellular formation of inositol-1,4,5-triphosphate (IP/) and 1,2-diacylglycerol. 1P> binds to a receptor that is located on the endoplasmic reticulum, initiating the release of Ca into the cytosol, where it activates Cade pendent protein kinases. Diacylglycerol activates protein kinase C. Additionally, stimulation of H] receptors may activate phospholipase A2 and trigger the arachidonic acid cascade, leading to prostaglandin production.

Hi receptors are associated with adenylate cyclase, and stimulation of these receptors increases the cytosolic concentration of cAMP and activation of cAMP-dependent protein kinase. Although inhibition of adenylate cyclase has been suggested as the intracellular signaling mechanism associated with 11>. receptors, this has not been completely substantiated.

338, The answer is a, (Katzung, pp 599-603.) Aspirin (acetylsalicylic acid) is the most extensively used analgesic, antipyretic, and anti-

inflammatory agent of the group of compounds known as NSAlDs, or nonopioid analgesics. Most of its therapeutic and adverse effects appear to be related to the inhibition of prostaglandin synthesis. Nonsteroidal antiinflammatory drugs inhibit the activity of the enzyme cyclooxygenase: which mediates the conversion of arachidonic acid to prostaglandins that are involved in pain, fever, and inflammation. Aspirin may produce irritation and ulceration of the gastrointestinal (GO tract, an adverse effect that is about equal to other salicylates. It also inhibits platelet aggregation. Acetaminophen, like aspirin, has analgesic and antipyretic properties, but it does not have clinically significant anti-inflammatory activity and is not irritating to the GI tract.

339, The answer is d. (Kalzung, p 275.) Cimetidine ts an 1 \1 antagonist that decreases gastric acid secretion. Sumatriptan is a 5-HT1D serotonin agonist. Cyproheptadine acts as a histamine and serotonin antagonist. Ondansetron is a serotonin antagonist. Fluoxetine is an antidepressant agent that selectively inhibits serotonin reuptake.

340, The answer is d. (Hardman, p 6 J 7. Katzung, p 318.) Most NSAlDs inhibit both cyclooxygenase I and II. resulting in decreased synthesis of prostaglandins, prostacyclins, and thromboxanes.

341, The answer is d, (Hardman, p 1354. Katzung„ pp 574-575J Ticlopi-dine decreases platelet aggregation by inhibiting the uptake of adenosine ^'-diphosphate (ADP) release during degranulation by circulating platelets. Ticlopidme has no effect on prostaglandin synthesis.

342, The answer is a. (Hardman, pp 469-470.) Phenytoin has a narrow toxic-therapeutic range. Early signs of phenytoin toxicity are diplopia, nystagmus, and ataxia; sedation occurs at higher drug levels. Gingival hypertrophy, hirsutism, peripheral neuropathy, and folate-deficiency anemia can occur with long-term use. Phenytoin toxicity can be induced by drugs that displace it from plasma proteins.

343, The answer is a. ('Hardman, p 510. Katzung, p 4677) Fluctuations in clinical response to L-dopa may or may not be related to drug levels (time of last dose). The likelihood of both kinds of fluctuation increases with longer duration of treatment. When these fluctuations are unrelated to drug levels, they are termed the on-off phenomenon; the mechanism is unclear

344, The answer is a. (Hardman, p 495.) Ergotamine has several pharmacologic properties, including the blockade of «-adrenergic receptors; however, its mechanism of action in treating migraine headaches is primarily related to its agonistic interaction with serotonin receptors (5-HT1D)t resulting in vasoconstriction. Although chronic treatment with this non sedative, n on analgesic drug does not decrease the frequency of or prevent migraine attacks, an oral dose of ergotamme is the drug of choice for combating an incipient attack of migraine headache, especially during the prodromal stage.

345, The answer is d. (Katzung, p 603.) Celocoxib is a eyelooxygenasell inhibitor. Aspirin, ibuprofen, and piroxicam are relatively nonselective inhibitors of eye looxygena ses. Acetaminophen has no effect on cyclo oxygenases.

346, The answer is h. (Hardman, pp 631-633.) All of the drugs listed, except acetaminophen, are usually considered NSAIDs, a large group of structurally dissimilar compounds. These drugs share the pharmacologic properties of the prototype compound, aspirin, in that all have analgesic, antipyretic, and ami-inflammatory effects. The mechanism of action that is responsible for the effect of NSAlDs is reduction in the formation of eicosanoids (e.g.. prostaglandins, thromboxanes) by inhibiting the enzyme cyclo oxygenase. Acetaminophen differs from the other drugs in that it is a very weak anti-inflammatory agent: however, it is an effective analgesic and antipyretic.

347, The answer is c. (Katzung pp 612, 1073J Sulfasalazine is a derivative of sulfapyridine and 5-aminosalicylic acid. It is not significantly absorbed following oral administration, The 5-aminosalicyclic acid moiety is released by intestinal bacterial action. Sulfasalazine is more effective in maintaining than causing remission in ulcerative colitis. Celocoxib (a selective cyclo oxygenase inhibitor), infliximab (a chimeric monoclonal antibody), and penicillamine (an analogue of cysteine) have a role in the treatment of rheumatoid arthritis. Naproxen, a nonselective cyclooxyge-nase inhibitor, is indicated for usual rheumatological indications.

348, The answer is cL (Kaiz^ng, pp 464-467J Adding carbidopa decreases the amount of dopamine that is formed peripherally from dopa by dopa decarboxylase. Depression, psychosis, and other psychiatric adverse effects of i.-dopa are mediated by CN5 dopamine, so adding carbidopa does not make them less likely The combination of L-dopa and carbidopa reduces the extracerebral metabolism of L-dopa, resulting in decreased peripheral adverse effects.

349, The answer is b, (Katzung, p 344.) Zileuton is a ^-lipoxygenase inhibitor. Although tt is not clear that leukotrienes are partly responsible for the symptoms of asthma, zileuton has a bronchodilator effect that is therapeutically efficacious. The 5-lipoxygenase inhibitors may be less effective than inhaled steroids, but they have the advantage that they are orally administered. This may be an advantage for those individuals who either reject steroid therapy or have difficulty using an inhaler.

350, The answer is c, (.Hardman} p 611.) Alprostadil [prostaglandin E: (PGEl)] is used, therapeutically in preterm infants to temporarily maintain the patency of the ductus arteriosus until corrective surgery can be performed. The drug is administered by continuous intravenous infusion or by catheter through the umbilical artery and should only be used in pediatric intensive care facilities. Misoprostol is a synthetic analogue of PGEl (15-deoxy-16-hydroxy-16-methyl-P(jEl methyl ester). It is indicated for the prevention of gastric ulcers in patients taking NSAlDs (e.g., aspitin, indomethacin) and is administered orally. Zafirleukast is a leukotriene receptor inhibitor, which can be used in asthma. Methysergide ts an ergot alkaloid and is used for prophylaxis in patients with migraine headaches. Timolol is a (3-adrenergic antagonist that is useful in the treatment of glaucoma.

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