Torsemide vs. Lasix: Differences, similarities, and which is better for you

Drug overview & main differences | Conditions treated | Efficacy | Insurance coverage and cost comparison | Side effects | Drug interactions | Warnings | FAQ

Torsemide and Lasix are two prescription medications used in the management of edema and hypertension, or high blood pressure. Edema is the accumulation of fluid in your tissues. In advanced cases, the accumulation of fluid causes a noticeable swelling of the extremities.

Torsemide and Lasix are both classified as diuretics, and specifically belong to a subclass known as loop diuretics. Diuretics in general are medications that help the body manage excess fluid.

What are the main differences between torsemide and Lasix?

Torsemide is a prescription-only drug and is known as a loop diuretic. It works in the kidneys, specifically in the ascending loop of Henle, by blocking sodium and chloride reabsorption through interference with sodium, potassium, and chloride cotransport. This results in the rapid excretion of water, sodium, and chloride by the kidneys into the urine. Torsemide is available as an oral tablet in strengths of 5 mg, 10 mg, 20 mg, and 100 mg. Torsemide is also available as a solution for injection in a concentration of 10 mg/ml.

Lasix is a prescription-only drug and is also a loop diuretic. Lasix also interferes with sodium, potassium, and chloride transport. This ultimately results in large amounts of water, sodium, potassium, and chloride being excreted by the body. Lasix is available as an oral tablet in strengths of 20 mg, 40 mg, and 80 mg. It is also available as a solution for injection in a concentration of 10 mg/ ml.

Conditions treated by torsemide and Lasix

Torsemide and Lasix are each used in the management of edema in patients with chronic and congestive heart failure and chronic renal failure. These are conditions of the heart and kidneys, respectively, which lead to the accumulation of fluid and can be life-threatening if not treated in a timely manner.

Chronic heart failure is a progressive condition in which the heart is unable to pump oxygenated blood through the body efficiently. Congestive heart failure is a more urgent condition where the heart has decompensated and become so inefficient at pumping that blood backs up in the body’s left side waiting to enter the left ventricle and then be oxygenated in the lungs. This phenomenon is also known as a reduced ventricular ejection fraction. This backup leads to edema, fluid retention in the tissues, and the use of diuretics helps to control the fluid overload. Acute heart failure syndrome refers to a change in symptoms of heart failure resulting in the immediate need for treatment. These terms are sometimes used interchangeably.

Torsemide and Lasix are both also used in the management of hypertension, or high blood pressure. Lasix is sometimes used off-label in the treatment of a hypertensive emergency. This is a condition where blood pressure is so high it can cause organ damage. A hypertensive emergency is defined as a systolic blood pressure over 180 mmHg or a diastolic blood pressure over 110 mmHg. The use of Lasix in this manner is considered off-label because it has not been approved by the Food and Drug Administration (FDA) for this indication.

The following chart may not list every use of torsemide or Lasix. Only your physician can determine if either of these drugs is appropriate for your condition.

Is torsemide or Lasix more effective?

A recent meta-analysis compared torsemide and Lasix in patients with congestive heart failure (CHF). This review encompassed nineteen studies and almost 20,000 patients. The results found that torsemide use was associated with a lower rate of hospitalization for CHF. Torsemide is also associated with a significantly higher number of patients achieving functional improvement in status as compared to furosemide. Functional improvement was defined as improving from class III/IV to class I/II as defined by the New York Heart Association (NYHA). Torsemide use was also associated with a lower risk of cardiac mortality.

A retrospective, cohort study published by the American College of Cardiology found that patients with heart failure who were hospitalized without prior use of a diuretic had lower mortality and re-hospitalization rates when discharged on a loop diuretic.

The pharmacokinetics and pharmacodynamics, or how the drugs function in the body, of torsemide and Lasix are different. Torsemide has a high bioavailability of about 80% after taking a dose orally. Lasix absorption is much less predictable, and the presence of food may delay the response. Torsemide is twice as potent as furosemide on a milligram to milligram comparison.

Based on these findings, your healthcare provider may choose to start with torsemide when treating your congestive heart failure, but Lasix would also be an acceptable choice. The American Heart Association (AHA) lists torsemide, Lasix, and one other loop diuretic, bumetanide, as acceptable treatment options for chronic heart failure. There are also other types of diuretics which may be used, including thiazide diuretics, in the treatment of heart failure. Only clinicians can decide which treatment is best for you.

Coverage and cost comparison of torsemide vs. Lasix

Torsemide is a generic, prescription medication that is generally covered by both commercial and Medicare prescription insurance plans. The price of torsemide without insurance is about $36. With a coupon from SingleCare, you can access your torsemide prescription for as little as $9.

Lasix is a brand-name, prescription medication that is generally covered by both commercial and Medicare prescription insurance plans. The price of brand-name Lasix without insurance can be more than $50. With a SingleCare coupon, you can get generic Lasix for as low as $4.

Common side effects of torsemide vs. Lasix

The actions of torsemide and Lasix may lead to some undesirable side effects and adverse events for some patients. Due to their mechanism, excessive urination is a common side effect. In most cases, it is recommended to take your dose of either torsemide or Lasix early in the day as excessive urination is typically more prominent in the hours shortly after taking your dose. Taking these medications later in the day or at night could lead to night time wakening due to the need to urinate, and this could negatively affect quality of life.

Headache and dizziness are reported with both torsemide and Lasix. These are typically more pronounced when you first begin therapy but should improve with time. If they do not improve or are especially bothersome, you should discuss these effects with your provider.

Diuretics do have beneficial effects on the heart’s efficiency, and these must be weighed against potential side effects. The following list is not intended to be all-inclusive of possible side effects of these medications. Please consult your pharmacist or healthcare professional for a complete list.

Source: DailyMed (Torsemide) DailyMed (Lasix)

RELATED: Lasix side effects and how to avoid them

Drug interactions of torsemide vs. Lasix

Torsemide, when administered with opiates such as codeine or fentanyl, may have a decreased diuretic effect. Torsemide and Lasix may also be much more likely to cause orthostatic hypotension in patients taking either drug with codeine. Orthostatic hypotension describes a condition of a sudden shift in blood pressure that occurs when you rise suddenly from sitting or lying down. It may leave you feeling dizzy, lightheaded, faint, nauseous, or confused. It may only last for a very short period of time. If it lasts for a prolonged period of time (more than a few minutes), you should discuss this with your doctor.

When taken with torsemide or Lasix, non-steroidal anti-inflammatory drugs (NSAIDs) may result in decreased kidney function and decreased diuretic effects. Celecoxib, a COX-2 NSAID, is metabolized by an enzyme that is inhibited by torsemide. This results in a potential for significantly higher plasma concentrations of celecoxib in the body. These higher plasma concentrations over time carry an increased risk of stroke and other serious cardiovascular events.

The following table is not meant to include all potential drug interactions. Please consult your physician or pharmacist for a complete list. Before you are given torsemide or Lasix, make sure your healthcare provider is aware of all medications you are taking.

Warnings of torsemide and Lasix

Torsemide and Lasix carry the risk of tinnitus and temporary or long-term hearing loss. This type of dysfunction appears to be most common when Lasix is administered by rapid injection, in patients with renal impairment, or when dosing these medications higher than recommended. It can also happen with oral torsemide therapy. For this reason, continuous intravenous infusion is preferred over rapid injection, and monitoring should be done in patients with renal insufficiency.

When using Lasix in the adjunct treatment of ascites, therapy is best initiated in a hospital setting. Sudden fluid depletion and electrolyte imbalance may precipitate a hepatic coma in patients with liver disease or cirrhosis. Monitoring of a patient’s baseline and ongoing status upon initializing therapy is best done in the hospital setting. The use of Lasix in ascites is only intended to be in addition to aldosterone antagonists.

Patients on any diuretics, including loop diuretics, are at risk for fluid depletion and electrolyte imbalance. Patients on torsemide and Lasix should be monitored for signs and symptoms such as dry mouth, thirst, weakness, lethargy, muscle pain and cramps, hypotension, and tachycardia (increased heart rate). Electrolyte imbalances may include high or low levels of chloride, sodium, and/or potassium. With loop diuretics, hypokalemia, or low potassium, is one of the most common electrolyte imbalances. Increased levels of blood urea nitrogen (BUN) may also occur. Your physician may do periodic bloodwork to monitor your electrolyte levels.

Frequently asked questions about torsemide vs. Lasix

What is torsemide?

Torsemide is a prescription medication used in the management of edema and hypertension. It is a loop diuretic and works by removing excess fluid from the interstitial space of tissues. Torsemide is available in oral tablets in strengths of 5 mg, 10 mg, and 20 mg. It is also available as an injectable solution in a concentration of 10 mg/ml.

What is Lasix?

Lasix is a prescription medication used in the management of edema and hypertension. It is also a loop diuretic. Lasix is available in oral tablets in strengths of 20 mg, 40 mg, and 80 mg. It is also available as an injectable solution in a concentration of 10 mg/ml.

Are torsemide and Lasix the same?

Torsemide and Lasix are both loop diuretics but are not exactly the same. Torsemide is twice as potent as Lasix. Lasix carries a broader range of indications for use.

Is torsemide or Lasix better?

Torsemide is associated with lower rates of hospitalizations for CHF as compared to Lasix. It is also associated with a higher level of clinical improvement in CHF patients and lower rates of mortality related to cardiovascular disease when compared directly to Lasix.

Can I use torsemide or Lasix while pregnant?

Torsemide is pregnancy category B, meaning no animal studies have shown fetal harm and there have been no studies in pregnant women. It should not be used unless absolutely necessary. Lasix is pregnancy category C, meaning there have been no well-controlled clinical trials to establish safety. Lasix should only be used when the benefits clearly outweigh the risks.

Can I use torsemide or Lasix with alcohol?

Alcohol consumption may lead to dehydration and electrolyte imbalance. Torsemide and Lasix, when taken with alcohol, may significantly increase the risk of severe dehydration and electrolyte imbalance.

Is torsemide more effective than furosemide in heart failure?

A recent meta-analysis comparing torsemide versus furosemide shows that torsemide may be associated with better clinical outcomes in heart failure patients as compared to furosemide, including lower hospitalization rates, improved functional status, and decreased cardiac morbidity. Torsemide also has a longer half-life and works for longer periods of time in the body.

Is torsemide hard on the kidneys?

Torsemide should be used very cautiously in patients with renal disease. Hypovolemia, or low fluid volume, caused by diuretic, can be especially dangerous in patients with pre-existing kidney disease.

What diuretic is stronger than Lasix?

Torsemide is twice as potent as Lasix in a milligram per milligram comparison and has been associated with improved clinical outcomes as compared to Lasix.

What is a substitute for Lasix?

Torsemide is a substitute for Lasix when clinical outcomes are not being reached with Lasix. They are both loop diuretics used in edema management and the treatment of hypertension, but torsemide has been shown to be more potent.