NEET-PG Pharmacology Previous Year Questions (2017–2026)

Correct answer: A. Rasburicase.

Rasburicase is recombinant urate oxidase; it enzymatically converts existing uric acid into highly soluble allantoin, so it removes the urate that is already present. This makes it far more effective than xanthine-oxidase inhibitors in established tumour-lysis syndrome, which only block further production. It is contraindicated in glucose-6-phosphate dehydrogenase deficiency (risk of haemolysis and methaemoglobinaemia).

Incorrect Options:

• B. Allopurinol: a xanthine-oxidase inhibitor that prevents new urate formation but cannot clear urate already made; it also dangerously raises 6-mercaptopurine levels.
  Allopurinol, a xanthine-oxidase inhibitor (prevention, not clearance).
• C. Febuxostat: also a xanthine-oxidase inhibitor; useful for prophylaxis but not for rapidly lowering an already-high urate.
  Febuxostat, a non-purine xanthine-oxidase inhibitor.
• D. Benzbromarone: a uricosuric that increases renal urate excretion; hazardous when tubules are already loaded with urate and hepatotoxic.
  Benzbromarone, a uricosuric agent.

High-Yield Facts:

• Rasburicase converts uric acid to soluble allantoin and lowers urate within hours.
• It is contraindicated in G6PD deficiency (haemolysis, methaemoglobinaemia).
• Allopurinol markedly increases thiopurine (6-mercaptopurine, azathioprine) toxicity - avoid or slash the dose.
• Xanthine-oxidase inhibitors prevent urate formation; rasburicase destroys urate already present.

Correct answer: B. Alvimopan.

Alvimopan is a peripherally acting mu-opioid receptor antagonist that does not cross the blood-brain barrier. It reverses the gut effects of opioids that cause constipation while leaving central analgesia intact, which is exactly what is needed here.

Incorrect Options:

• A. Diphenoxylate: itself an opioid used to treat diarrhoea; it would worsen, not relieve, constipation.
  Diphenoxylate, an opioid antidiarrhoeal.
• C. Naltrexone: a centrally penetrant opioid antagonist that would abolish the required analgesia and precipitate withdrawal.
  Naltrexone, a central opioid antagonist.
• D. Erythromycin: a motilin-receptor agonist prokinetic for gastroparesis, not the specific treatment for opioid-induced constipation.
  Erythromycin, a motilin-agonist prokinetic.

High-Yield Facts:

• Peripherally acting mu-opioid antagonists (alvimopan, methylnaltrexone, naloxegol) treat opioid-induced constipation without losing analgesia.
• They do not cross the blood-brain barrier, so central pain relief is preserved.
• Naltrexone and naloxone act centrally and reverse analgesia.
• Alvimopan is also used to speed recovery of bowel function after bowel resection.

Correct answer: D. Direct stimulation of soluble guanylate cyclase.

Vericiguat is an oral soluble guanylate cyclase (sGC) stimulator. It directly stimulates the enzyme and also sensitises it to endogenous nitric oxide, raising cyclic GMP to promote vasodilatation and reduce myocardial and vascular remodelling in heart failure with reduced ejection fraction.

Incorrect Options:

• A. Blocks PDE-5 cGMP breakdown: that is the mechanism of sildenafil, which prevents cyclic GMP degradation rather than driving its synthesis.
  Sildenafil, a phosphodiesterase-5 inhibitor.
• B. Inhibits neprilysin activity: that is sacubitril, which raises natriuretic peptides, a different pathway.
  Sacubitril, a neprilysin inhibitor.
• C. NO-dependent sGC stimulation: describes riociguat, which augments the enzyme mainly in the presence of nitric oxide; vericiguat also has direct, NO-independent activity.
  Riociguat, used mainly in pulmonary hypertension.

High-Yield Facts:

• The nitric-oxide - sGC - cyclic GMP axis drives smooth-muscle relaxation.
• Vericiguat is approved for symptomatic chronic heart failure with reduced ejection fraction after a worsening event (VICTORIA trial).
• Riociguat, the related sGC stimulator, is used chiefly in pulmonary arterial hypertension.
• Combining an sGC stimulator with a PDE-5 inhibitor or nitrates risks severe hypotension.