Final answer:
Frusemide, a loop diuretic, is the least likely drug to cause hyperkalemia (high potassium levels) in a hypertensive patient, as it promotes the excretion of potassium, unlike ACE inhibitors or Spironolactone which are known to increase potassium levels.
Step-by-step explanation:
The question addresses the issue of hyperkalemia in a hypertensive patient, which is an elevated potassium level in the blood. Among the drugs listed, Frusemide is a loop diuretic and is the least likely to cause hyperkalemia. Loop diuretics like Frusemide work by inhibiting the reabsorption of sodium (Na+) and chloride (Cl-) in the ascending limb of the loop of Henle in the kidneys. This inhibition leads to increased urination and the excretion of potassium, which would commonly lead to lower serum potassium levels, not higher levels, in contrast to what is observed with the potassium of 6.7 mentioned in the question.
Conversely, drugs like ACE inhibitors and Spironolactone are known to increase serum potassium levels and could be more likely contributors to hyperkalemia. Suxamethonium is a muscle relaxant used in anesthesia that can also increase potassium levels, especially in patients with high risk factors such as burns, neuromuscular diseases, or renal failure. Therefore, when considering a drug that is least likely associated with a high potassium level of 6.7, Frusemide stands out as it typically causes the excretion of potassium, lowering serum levels.