Step 1: Understanding the Concept:
A pFox inhibitor is an anti-anginal drug that shifts the heart's energy source away from fatty acids and toward glucose, without changing heart rate, blood pressure, or blood vessel diameter.
Step 2: Key Formula or Approach:
Sort the four drugs by mechanism first: is the drug acting on the heart's fuel metabolism, or is it acting on receptors, channels, or vessels elsewhere in the body. Only a fuel-metabolism drug can be a pFox inhibitor.
Step 3: Detailed Explanation:
Trimetazidine blocks the enzyme long chain 3-ketoacyl CoA thiolase inside heart muscle cells, so fatty acid breakdown slows down and glucose breakdown speeds up. Glucose needs less oxygen per unit of energy produced, so the heart works more efficiently on the same oxygen supply.
Atosiban acts on oxytocin receptors in the uterus, not on heart metabolism.
Verapamil and nicardipine both block calcium channels in vessel and heart muscle, lowering blood pressure and oxygen demand through vessel relaxation, not through a fuel switch.
Step 4: Final Answer:
Trimetazidine is the drug that works by shifting cardiac metabolism from fatty acids to glucose, which makes it the pFox inhibitor among the four options.