SNLE Pharmacology

Question 1

What is the meaning of 'therapeutic index'?

Accepted Answer

The ratio between the toxic dose and the therapeutic dose of a drug

Answer

The therapeutic index (TI) = TD50/ED50 (toxic dose in 50% / effective dose in 50%). A narrow TI means the difference between effective and toxic doses is small, requiring careful monitoring (e.g., lithium, digoxin, warfarin, aminoglycosides).

Question 2

Which phase of pharmacokinetics describes the breakdown of a drug into metabolites?

Accepted Answer

Metabolism (biotransformation)

Answer

Metabolism (biotransformation) involves enzymatic conversion of drugs into metabolites, primarily in the liver via cytochrome P450 enzymes. Metabolites may be active or inactive. Drug-drug interactions often occur at this phase. Absorption: drug enters bloodstream; distribution: drug spreads to tissues; excretion: drug leaves the body.

Question 3

A patient is taking digoxin. Which electrolyte imbalance increases the risk of digoxin toxicity?

Accepted Answer

Hypokalemia (low potassium)

Answer

Hypokalemia increases digoxin toxicity by increasing the drug's binding to the Na+/K+-ATPase pump (same site as potassium). Low potassium and digoxin compete for the same receptor — with less potassium, digoxin binds more and exerts a more potent (toxic) effect.

Question 4

What is the antidote for acetaminophen (paracetamol) overdose?

Accepted Answer

N-acetylcysteine (NAC)

Answer

N-acetylcysteine (NAC) is the specific antidote for acetaminophen toxicity. Acetaminophen overdose depletes glutathione, allowing the toxic metabolite NAPQI to cause hepatic necrosis. NAC replenishes glutathione and detoxifies NAPQI. It must be given within 8–10 hours for maximum efficacy.

Question 5

A patient is prescribed metformin for type 2 diabetes. What is the most serious adverse effect to monitor for?

Accepted Answer

Lactic acidosis, particularly in renal impairment

Answer

Metformin-associated lactic acidosis (MALA) is rare but life-threatening, occurring when metformin accumulates due to renal impairment (reduced excretion). Metformin is contraindicated in significant renal failure (eGFR <30 mL/min). Hypoglycemia is rare with metformin alone.

SNLE Practice Test

SNLE Practice Test

SNLE Pharmacology