A client with heart failure is prescribed furosemide (Lasix). What is the primary mechanism and a key adverse effect?

Furosemide (Lasix) is a loop diuretic — the most potent class of diuretic. Mechanism: inhibits the sodium-potassium-chloride co-transporter in the ascending loop of Henle, causing large amounts of sodium, chloride, potassium, and water to be excreted. Used for: heart failure, edema, hypertension, ascites. Adverse effects: (1) Hypokalemia — can cause weakness, arrhythmias; monitor K+ and supplement as needed; (2) Hyponatremia and other electrolyte imbalances; (3) Dehydration and hypotension — monitor weight (best indicator of fluid status), blood pressure, orthostatic changes; (4) Ototoxicity — especially with rapid IV administration of high doses, or combined with other ototoxic drugs (aminoglycosides); give IV slowly; (5) Hyperglycemia, hyperuricemia (can trigger gout); (6) Photosensitivity. Teaching: take in morning to avoid nocturia; rise slowly to prevent orthostatic hypotension; eat potassium-rich foods (bananas, oranges, leafy greens) unless on potassium-sparing diuretic. Daily weight monitoring (same time, same scale, same clothing) — report gain over 2 lbs in a day or 5 lbs in a week.