Metolazone Versus Furosemide (Lasix)
Metolazone is a thiazide-like diuretic that inhibits sodium reabsorption in the distal convoluted tubule. [1] Furosemide is a loop diuretic that inhibits sodium and chloride reabsorption in the thick ascending limb of the loop of Henle. [2]
Drug Class and Primary Nephron Segment
Metolazone is a thiazide-like diuretic that acts in the distal convoluted tubule. [1] Furosemide is a loop diuretic that acts in the thick ascending limb of the loop of Henle. [2]
Transporter Target and Mechanism of Action
Metolazone inhibits the Na-Cl cotransporter (NCC) in the distal convoluted tubule. [3] Furosemide inhibits the Na-K-2Cl cotransporter (NKCC2) in the thick ascending limb. [2]
Clinical Implication of Different Sites of Action
Metolazone has diuretic efficacy in settings of low glomerular filtration rate because it acts at a more distal nephron site than loop diuretics. [4] Furosemide primarily depends on effective delivery of drug to the loop of Henle for blockade of NKCC2. [6]
Duration of Action
Metolazone has an elimination half-life of approximately 6–8 hours. [1] Furosemide has a shorter half-life of about 1.5–2 hours. [2]
Typical Electrolyte Pattern
Both metolazone and furosemide increase urinary sodium and chloride delivery to downstream nephron segments. [1], [2] Metolazone and furosemide can both contribute to potassium loss, but the magnitude and clinical consequences depend on dosing, renal function, and concurrent diuretic use. [1], [2]
Practical Use of the Combination Concept
Metolazone is often paired with a loop diuretic when distal sodium reabsorption escape limits the response to loop diuretic monotherapy. [7]
Pharmacologic Differentiators to Remember
Metolazone is thiazide-like and targets the distal convoluted tubule (NCC). [1] Furosemide is loop diuretic and targets the thick ascending limb (NKCC2). [2] Metolazone generally has a longer half-life than furosemide. [1], [2]