Flushing caused by this drug can be reduced by taking it after meals and/or by pretreatment with aspirin:

Correct Answer: B

Rationale: The correct answer is B, Nicotinic acid (niacin). Niacin commonly causes flushing as a side effect due to prostaglandin release. Taking it after meals can slow down absorption and reduce flushing. Pretreatment with aspirin also helps by inhibiting prostaglandin synthesis. Lovastatin (A), Gemfibrozil (C), and Probucol (D) do not cause flushing as a side effect, so the strategies of taking after meals or pretreatment with aspirin would not be effective for reducing flushing caused by these drugs.

Correct Answer: B

Rationale: The correct answer is B: Furosemide (Lasix). Furosemide is a loop diuretic that inhibits sodium and chloride transport in the cortical thick ascending limb. This leads to increased excretion of these ions and water. Acetazolamide (A) inhibits carbonic anhydrase in the proximal tubule, Hydrochlorothiazide (C) acts on the distal convoluted tubule, and Amiloride (D) inhibits sodium reabsorption in the collecting duct. Therefore, only Furosemide affects sodium and chloride transport in the cortical thick ascending limb.

Correct Answer: C

Rationale: The correct answer is C: Lincomycin. Lincomycin is not a macrolide antibiotic, unlike the other options. Macrolide antibiotics have a macrocyclic lactone ring structure, which is absent in Lincomycin. Erythromycin, Clarithromycin, and Roxythromycin are macrolides with a similar structure and mechanism of action as they inhibit bacterial protein synthesis by binding to the 50S ribosomal subunit. Therefore, Lincomycin is the correct answer as it does not belong to the macrolide class of antibiotics.

Correct Answer: B

Rationale: The correct answer is B: Infections of urinary and gastrointestinal tracts. Nitrofuranes are commonly used to treat urinary tract infections and certain gastrointestinal infections due to their effectiveness against a variety of bacteria commonly found in these areas. Nitrofuranes are not typically used to treat respiratory infections (choice A), syphilis (choice C), or tuberculosis (choice D) as there are more appropriate antibiotics available for these conditions. Therefore, choice B is the correct indication for nitrofuranes based on their spectrum of activity and clinical effectiveness.

Correct Answer: C

Rationale: Step-by-step rationale: 1. Nonnucleoside reverse transcriptase inhibitors (NNRTIs) bind to the enzyme reverse transcriptase. 2. Nevirapine is an NNRTI that inhibits HIV-1 reverse transcriptase. 3. Zidovudine (A) is a nucleoside reverse transcriptase inhibitor. 4. Vidarabine (B) is a nucleoside analog antiviral medication. 5. Gancyclovir (D) is a nucleoside analog antiviral used for herpesvirus infections. Summary: Choice C (Nevirapine) is the correct answer as it belongs to the class of NNRTIs by inhibiting reverse transcriptase enzyme. Choices A, B, and D are incorrect as they belong to the class of nucleoside analog antivirals, not NNRTIs.