A 22-year-old woman presents with severe salicylate overdose. Intravenous sodium bicarbonate is administered as part of management. The mechanism by which this enhances salicylate elimination is:
- A Increasing glomerular filtration rate
- B Competitive inhibition of renal tubular secretion
- C Ion trapping of salicylate in alkaline urine, reducing tubular reabsorption ✓
- D Induction of hepatic microsomal enzymes metabolizing salicylate
Correct answer: C. Ion trapping of salicylate in alkaline urine, reducing tubular reabsorption
Explanation
Salicylate is a weak acid. Alkalinizing urine with sodium bicarbonate converts it to its ionized form, which cannot cross lipid membranes and is trapped in the tubular lumen, enhancing renal excretion. This ion-trapping mechanism does not rely on GFR changes, competitive secretion inhibition, or enzyme induction. Urine pH above 7.5 significantly increases salicylate clearance.
Reference: Katzung Basic and Clinical Pharmacology, 15th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
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