Which of the following drugs used in the treatment of gout has as its primary effect the reduction of uric acid synthesis:

Correct Answer: A

Rationale: Allopurinol is the correct answer as it inhibits xanthine oxidase, an enzyme involved in uric acid synthesis. By reducing the conversion of hypoxanthine to xanthine and xanthine to uric acid, allopurinol effectively lowers uric acid levels. Sulfinpyrazone increases uric acid excretion, not synthesis. Colchicine works by reducing inflammation in gout attacks, not affecting uric acid levels. Indomethacin is a nonsteroidal anti-inflammatory drug that alleviates gout symptoms but does not target uric acid synthesis.

Correct Answer: B

Rationale: The correct answer is B: Ascending thick limb of the loop of Henle. Furosemide inhibits the Na+/K+/2Cl- symporter in this nephron segment, leading to decreased reabsorption of sodium, chloride, and water. This mechanism of action results in increased diuresis. The other choices (A, C, D) represent different nephron segments where Furosemide does not primarily act. In the proximal convoluted tubule (A), it mainly inhibits the Na+/K+/2Cl- symporter, and in the distal convoluted tubule (C) and collecting duct (D), it has minimal impact on sodium reabsorption.

Correct Answer: D

Rationale: Step-by-step rationale for why answer D is correct: 1. Vancomycin is a glycopeptide antibiotic known to inhibit cell wall synthesis. 2. It is effective against Gram-positive bacteria such as Staphylococcus and Streptococcus. 3. Vancomycin is not active against Gram-negative bacteria due to differences in cell wall structure. 4. Options A, B, and C are incorrect as they provide inaccurate information about vancomycin's characteristics.

Correct Answer: A

Rationale: Certainly! Chloroquine is the correct answer for malaria chemoprophylaxis and treatment because it is effective against Plasmodium species. It acts by accumulating in the parasite's food vacuole, interfering with heme polymerization. This prevents the parasite from utilizing hemoglobin and ultimately leads to its death. Quinidine and quinine are primarily used for severe malaria treatment. Sulfonamides are not commonly used for malaria treatment due to resistance issues and their limited efficacy against Plasmodium species.

Correct Answer: B

Rationale: The correct answer is B: Zalcitabine. Zalcitabine is a nucleoside reverse transcriptase inhibitor commonly associated with peripheral neuropathy and oral ulceration as side effects. These adverse effects are well-documented in clinical studies and are known to be dose-dependent. Zalcitabine can cause damage to peripheral nerves leading to neuropathy and can also irritate the mucous membranes in the mouth causing oral ulceration. Incorrect Choices: A: Acyclovir - Acyclovir is an antiviral medication used to treat herpes infections and does not typically cause peripheral neuropathy or oral ulceration. C: Zidovudine - Zidovudine is also a nucleoside reverse transcriptase inhibitor used in the treatment of HIV, but it is not associated with peripheral neuropathy or oral ulceration. D: Saquinavir - Saquinavir is a protease inhibitor used to treat HIV and does not commonly induce peripheral neurop