Which medication should a nurse withhold if a client has a potassium level of 3.2 mEq/L?

Furosemide, a loop diuretic, promotes the excretion of sodium and water, but it also causes the kidneys to excrete potassium. In a client with a potassium level of 3.2 mEq/L, which indicates hypokalemia (low potassium), administering furosemide could exacerbate the already low potassium level and lead to serious complications such as arrhythmias or cardiac issues.

In contrast, the other medications listed—aspirin, metoprolol, and lisinopril—do not have the same direct effect on potassium levels. While some of these medications may interact with potassium levels in certain contexts (for example, lisinopril can increase potassium levels), they do not lower it like furosemide does. Therefore, in the context of hypokalemia, furosemide should be withheld to prevent further lowering of potassium levels and potential harm to the client.