Which medication should be avoided in patients with severe renal impairment due to risk of accumulation and toxicity?

Metformin is a medication that should be avoided in patients with severe renal impairment because it is primarily eliminated through the kidneys. In patients with compromised kidney function, the reduced ability to excrete the drug can lead to accumulation, increasing the risk of serious adverse effects, most notably lactic acidosis. This condition is a rare but life-threatening complication associated with the buildup of metformin in the body. It is crucial to assess renal function, particularly in patients who may have pre-existing kidney issues, before initiating or continuing therapy with metformin.

While other medications listed can also pose risks in patients with renal impairment, metformin's direct association with renal elimination and the specific risk of lactic acidosis makes it particularly critical to avoid in individuals with severe kidney dysfunction.