Final answer:
The combination of Potassium-sparing diuretics and calcium channel blockers can lead to potential contraindications due to the increased risk of high potassium levels.
Step-by-step explanation:
Among the drug class combinations listed, the potential contraindications are most likely to occur with the combination of Potassium-sparing diuretics and calcium channel blockers. Potassium-sparing diuretics can cause hyperkalemia, or high potassium levels, while calcium channel blockers can also increase potassium levels in the blood. Therefore, the combination of these two drug classes may result in dangerously high potassium levels.