What is the information about Torsemide (Loop Diuretic)?

From the Guidelines

Torsemide is a potent loop diuretic medication that should be used at doses ranging from 5-200 mg daily, with careful monitoring of electrolytes, particularly potassium and magnesium levels, due to its potential to cause electrolyte imbalances and dehydration, as evidenced by studies such as 1 and 1.

Key Points

• Torsemide works by inhibiting the sodium-potassium-chloride cotransporter in the ascending loop of Henle in the kidneys, preventing sodium and water reabsorption and increasing urine output.
• It has several advantages over other loop diuretics like furosemide, including better oral bioavailability (approximately 80-90%), longer duration of action (12-16 hours versus 6-8 hours for furosemide), and more consistent absorption regardless of food intake or gastrointestinal edema.
• Common side effects include electrolyte imbalances (particularly potassium depletion), dehydration, dizziness, headache, and increased urination.
• Patients taking torsemide should have their electrolytes monitored regularly, especially potassium and magnesium levels, as recommended by guidelines such as 1 and 1.
• Torsemide may interact with other medications including NSAIDs, aminoglycosides, lithium, and ACE inhibitors, potentially affecting efficacy or increasing risk of adverse effects, as noted in studies such as 1 and 1.

Dosage and Administration

• Torsemide is typically prescribed at doses ranging from 5-200 mg daily, with 10-20 mg being common for heart failure and edema, while lower doses of 5-10 mg may be used for hypertension.
• The maximum daily dose of torsemide is 200 mg, with a duration of action of 12-16 hours, as shown in Table 4 of 1.

Monitoring and Precautions

• Patients taking torsemide should be monitored regularly for signs of electrolyte imbalances, dehydration, and other potential side effects.
• Renal function should be monitored closely, especially in patients with pre-existing kidney disease, as torsemide can cause a decline in renal function, as noted in studies such as 1.

From the FDA Drug Label

1. 1 Mechanism of Action Micropuncture studies in animals have shown that torsemide acts from within the lumen of the thick ascending portion of the loop of Henle, where it inhibits the Na+/K+/2Cl–-carrier system. Torsemide increases the urinary excretion of sodium, chloride, and water, but it does not significantly alter glomerular filtration rate, renal plasma flow, or acid-base balance.
2. 2 Pharmacodynamics With oral dosing, the onset of diuresis occurs within 1 hour and the peak effect occurs during the first or second hour and diuresis lasts about 6 to 8 hours.
3. 3 Pharmacokinetics Absorption The bioavailability of torsemide tablets is approximately 80%, with small inter-subject variation; the 90% confidence interval is 75% to 89%. Torsemide is metabolized by the hepatic cytochrome CYP2C9 and, to a minor extent, CYP2C8 and CYP2C18. In normal subjects the elimination half-life of torsemide is approximately 3. 5 hours.

Key Points:

• Mechanism of Action: Torsemide acts by inhibiting the Na+/K+/2Cl–-carrier system in the loop of Henle.
• Pharmacodynamics: Onset of diuresis occurs within 1 hour, peak effect within 1-2 hours, and diuresis lasts 6-8 hours.
• Pharmacokinetics: Bioavailability is approximately 80%, and elimination half-life is approximately 3.5 hours.
• Metabolism: Torsemide is metabolized by CYP2C9, CYP2C8, and CYP2C18. 2

From the Research

Overview of Torsemide

• Torsemide is a loop diuretic that belongs to the pyridine-sulfonylurea class 3
• It is a high-ceiling diuretic with a longer half-life, longer duration of action, and higher bioavailability compared to furosemide 4, 5
• Torsemide has additional actions such as antialdosterone and vasodilatation effects 5

Mechanism of Action

• Torsemide blocks active reabsorption of sodium and chloride in the thick ascending limb of the loop of Henle, resulting in diuresis, natriuresis, and other effects 3
• It has a primary site of activity in the thick ascending limb of the loop of Henle 3

Clinical Efficacy

• Torsemide is effective in the treatment of hypertension and of edema and other symptoms in patients with chronic renal failure (CRF), hepatic dysfunction, or congestive heart failure (CHF) 3, 4
• It has been shown to improve left ventricular function, reduce mortality, and decrease the frequency and duration of heart failure-related hospitalization 5
• Torsemide also increases exercise tolerance, improves New York Heart Association functional classification, and quality of life in patients with CHF 5

Safety and Tolerability

• Torsemide is well tolerated in dosages up to 20 mg/day for at least 1 year 4
• The most commonly reported adverse effects are those associated with loop diuretics in general, including transient hypokalaemia, hyperuricaemia, dizziness, headache, gastrointestinal disturbances, orthostatic hypotension, and fatigue 4
• Torsemide has lesser ototoxicity compared to other loop diuretics 6

Dosage and Administration

• The recommended initial oral dosages of torsemide are 10-20 mg/day for CHF, 20 mg/day for CRF, 5 mg/day for hypertension, and 5-10 mg/day (in combination with a potassium-sparing diuretic or aldosterone antagonist) for hepatic cirrhosis 3
• Torsemide can be administered orally or intravenously, with a prolonged-release formulation available 5