What is the major box warning associated with Furosemide?

Furosemide, a loop diuretic, carries a major box warning primarily to highlight the significant risk of fluid and electrolyte loss associated with its use. This is critical because furosemide acts by inhibiting the reabsorption of sodium and chloride in the ascending limb of the loop of Henle, promoting diuresis and leading to increased urine production. As a result, patients may experience significant reductions in fluid volume and imbalances in electrolytes such as potassium and magnesium. Monitoring is essential to prevent complications such as dehydration, hypokalemia, and other electrolyte disturbances, which can have serious consequences, including cardiac arrhythmias.

When considering the other options, while cardiac arrest can occur in extreme cases of electrolyte imbalance, it is not the primary concern directly associated with furosemide's mechanism of action. Severe allergic reactions are not a routine warning tied to furosemide, making this option less relevant. Kidney failure may occur in cases of severe dehydration or electrolyte imbalance but is not emphasized as the main risk in the product labeling. Thus, the major box warning regarding fluid and electrolyte loss is particularly crucial for ensuring safe use of furosemide in clinical practice.