INI-CET 2013 — Pharmacology

Q: Which of the following statements about methyl alcohol poisoning is incorrect?

Fomepizole competitively inhibits aldehyde dehydrogenase. ***Fomepizole competitively inhibits aldehyde dehydrogenase*** - **Fomepizole** acts as a competitive inhibitor of **alcohol dehydrogenase**, not aldehyde dehydrogenase. - By inhibiting alcohol dehydrogenase, fomepizole prevents the metabolism of methanol into toxic metabolites like formic acid. *Effects are due to formic acid* - This statement is correct. The primary toxicity of methanol poisoning is due to its metabolism into **formic acid** by alcohol and aldehyde dehydrogenases. - Formic acid is responsible for the **metabolic acidosis** and **ocular toxicity** observed. *Metabolic acidosis* - This statement is correct. Methanol poisoning leads to severe **anion gap metabolic acidosis** due to the accumulation of formic acid. - The acidosis contributes significantly to the overall toxicity and clinical manifestations. *Blindness* - This statement is correct. **Blindness** is a classic and feared complication of methanol poisoning. - **Formic acid** specifically targets the **optic nerve** and retina, leading to **optic neuropathy** and permanent vision loss. [Practice more Pharmacology PYQs on OnCourse]

Q: A patient on amphotericin B develops hypokalemia with a potassium level of 2.3 mEq/L. What is the appropriate K+ supplementation required for this patient?

80 mEq over 24 hours. ***80 mEq over 24 hours***- For a potassium level of 2.3 mEq/L (moderate to severe hypokalemia), **80 mEq over 24 hours** represents appropriate aggressive replacement while maintaining safety.- This dose accounts for both the **existing deficit** and **ongoing renal potassium wasting** caused by amphotericin B, which impairs renal tubular function.- Standard guidelines recommend **60-80 mEq daily** for moderate to severe hypokalemia, divided into multiple doses with continuous cardiac monitoring.- Higher doses risk **rebound hyperkalemia** and cardiac complications [1]; replacement should be titrated based on serial potassium measurements.*40 mEq over 24 hours*- This dosage is insufficient for correcting a potassium level of 2.3 mEq/L, particularly with **ongoing drug-induced renal losses**.- It may be appropriate for mild hypokalemia (3.0-3.5 mEq/L) or maintenance therapy, but not for this clinical scenario.*60 mEq over 24 hours*- While this represents a reasonable starting dose for moderate hypokalemia, it may be **insufficient** given the severity (K+ 2.3 mEq/L) and ongoing losses from amphotericin B.- This dose might require escalation after reassessment of potassium levels.*100-120 mEq over 24 hours*- This dose **exceeds standard safe replacement protocols** and risks causing rebound hyperkalemia and cardiac arrhythmias [1].- Maximum safe infusion rates are typically **10-20 mEq/hour** (up to 40 mEq/hour only in critical situations with intensive monitoring).- Such aggressive replacement is not recommended in standard clinical practice for this scenario. [Practice more Pharmacology PYQs on OnCourse]

2 Previous Year Questions with Answers & Explanations

Questions

All Subjects Biochemistry (2)Forensic Medicine (1)Obstetrics and Gynecology (2)Ophthalmology (1)Orthopaedics (1)Pediatrics (2)Pharmacology (2)Surgery (1)

Which of the following statements about methyl alcohol poisoning is incorrect?

A patient on amphotericin B develops hypokalemia with a potassium level of 2.3 mEq/L. What is the appropriate K+ supplementation required for this patient?

INI-CET 2013 - Pharmacology INI-CET Practice Questions and MCQs

Question 1: Which of the following statements about methyl alcohol poisoning is incorrect?

A. Effects are due to formic acid
B. Metabolic acidosis
C. Blindness
D. Fomepizole competitively inhibits aldehyde dehydrogenase (Correct Answer)

Explanation: ***Fomepizole competitively inhibits aldehyde dehydrogenase*** - **Fomepizole** acts as a competitive inhibitor of **alcohol dehydrogenase**, not aldehyde dehydrogenase. - By inhibiting alcohol dehydrogenase, fomepizole prevents the metabolism of methanol into toxic metabolites like formic acid. *Effects are due to formic acid* - This statement is correct. The primary toxicity of methanol poisoning is due to its metabolism into **formic acid** by alcohol and aldehyde dehydrogenases. - Formic acid is responsible for the **metabolic acidosis** and **ocular toxicity** observed. *Metabolic acidosis* - This statement is correct. Methanol poisoning leads to severe **anion gap metabolic acidosis** due to the accumulation of formic acid. - The acidosis contributes significantly to the overall toxicity and clinical manifestations. *Blindness* - This statement is correct. **Blindness** is a classic and feared complication of methanol poisoning. - **Formic acid** specifically targets the **optic nerve** and retina, leading to **optic neuropathy** and permanent vision loss.

Question 2: A patient on amphotericin B develops hypokalemia with a potassium level of 2.3 mEq/L. What is the appropriate K+ supplementation required for this patient?

A. 40 mEq over 24 hours
B. 80 mEq over 24 hours (Correct Answer)
C. 60 mEq over 24 hours
D. 100-120 mEq over 24 hours

Explanation: ***80 mEq over 24 hours***- For a potassium level of 2.3 mEq/L (moderate to severe hypokalemia), **80 mEq over 24 hours** represents appropriate aggressive replacement while maintaining safety.- This dose accounts for both the **existing deficit** and **ongoing renal potassium wasting** caused by amphotericin B, which impairs renal tubular function.- Standard guidelines recommend **60-80 mEq daily** for moderate to severe hypokalemia, divided into multiple doses with continuous cardiac monitoring.- Higher doses risk **rebound hyperkalemia** and cardiac complications [1]; replacement should be titrated based on serial potassium measurements.*40 mEq over 24 hours*- This dosage is insufficient for correcting a potassium level of 2.3 mEq/L, particularly with **ongoing drug-induced renal losses**.- It may be appropriate for mild hypokalemia (3.0-3.5 mEq/L) or maintenance therapy, but not for this clinical scenario.*60 mEq over 24 hours*- While this represents a reasonable starting dose for moderate hypokalemia, it may be **insufficient** given the severity (K+ 2.3 mEq/L) and ongoing losses from amphotericin B.- This dose might require escalation after reassessment of potassium levels.*100-120 mEq over 24 hours*- This dose **exceeds standard safe replacement protocols** and risks causing rebound hyperkalemia and cardiac arrhythmias [1].- Maximum safe infusion rates are typically **10-20 mEq/hour** (up to 40 mEq/hour only in critical situations with intensive monitoring).- Such aggressive replacement is not recommended in standard clinical practice for this scenario.