After assessing a client, the nurse finds elevated BUN and creatinine levels. Which medication should the nurse question?

In the context of elevated BUN and creatinine levels, Amphotericin B is the medication that should raise a nurse's concern. This medication is known to be nephrotoxic, meaning it can cause damage to the kidneys, particularly when renal function is already impaired, as indicated by elevated levels of BUN (Blood Urea Nitrogen) and creatinine.

When a patient's renal function is compromised, the use of nephrotoxic drugs like Amphotericin B can exacerbate existing kidney issues, leading to further renal deterioration. Therefore, it is critical for nurses to question the administration of this medication in clients exhibiting signs of renal impairment to prevent potential worsening of their condition.

In comparison, the other medications listed tend to have different profiles concerning kidney function. Metformin, while contraindicated in severe renal impairment, is not directly nephrotoxic. Atorvastatin and Levothyroxine do not have significant nephrotoxic effects and their use is typically continued unless there are other clear contraindications. This highlights the importance of assessing renal function before administering medications that could exacerbate kidney-related issues.