Features June 2013 Issue

Least-Prescribed Loop Diuretic May Be Most Helpful for Heart Failure Patients

Research shows that torsemide’s effects may last longer and be better tolerated, but the drug is pricier and some doctors say a weaker diuretic is adequate for many people.

Loop diuretics are commonly prescribed to heart failure patients because they help reduce fluid buildup in the body, a common problem facing these individuals. But a recent study shows that of the three major types of loop diuretics, the one that may be the most effective is also the least prescribed.

Research, published in the Journal of the American College of Cardiology, found that between torsemide, furosemide and bumetanide, torsemide was shown to be more effective and better tolerated than the other two. However, torsemide also tends to be more expensive.

Cleveland Clinic cardiologist and heart failure specialist Eileen Hsich, MD, calls the study results “thought provoking,” but she adds that a large prospective study would better determine if one loop diuretic should be preferred over the others.

“Torsemide is a very effective loop diuretic because of its higher bioavailability,” Dr. Hsich says, referring to the amount or rate at which the drug is accessible to the body. “However, at equipotent doses all loop diuretics can cause similar amounts of urine to be excreted.”

How Diuretics Work
All loop diuretics are potent pills that cause you to urinate fluid. They are referred to as “loop” diuretics because the mechanism of action in the kidney is at the loop of Henle, named after F. G. J. Henle, who discovered these loops.

The loop of Henle is between the proximal and distal convoluted tubules in the kidney, and these tubules are part of the nephron or structure of the kidney that produces urine, and helps rid the bloodstream of waste products.

Loop diuretics inhibit sodium, chloride and potassium channels in the loop of Henle and result in reduced reabsorption of fluid and sodium back into the body. This leads to greater excretion in the urine of fluid and salts, Dr. Hsich explains.

Furosemide, bumetanide and torsemide are all types of loop diuretics known as sulfonamide derivatives. 

“It is important to mention that all loop diuretics may not be absorbed in the stomach in the setting of extreme volume overload,” Dr. Hsich says. “During this state, the wall of the gastrointestinal tract may also have excess fluid preventing absorption of medications, like a wet sponge that can no longer absorb fluid. When this occurs, the medication should be given intravenously to promote urination.”

Typically though, loop diuretics are taken orally, but your response to these medications, especially when you’re just starting or are changing the type or dose of a diuretic bears close supervision by your doctor.

Dosing Diuretics
The dosing of these medications is critically important, Dr. Hsich says, in part because the risk of dehydration is great if a patient takes more medication than is needed for his or her condition. There are other concerns as well, which is why Dr. Hsich typically tries to see patients within three days after starting with a new diuretic or a new dose.

Usually, when a patient is starting out with a loop diuretic, he or she will be given a low dose at first that can be increased as needed. One of the most commonly prescribed loop diuretics is furosemide (Lasix), and Dr. Hsich says it’s usually sufficient for most patients. Furosemide is also an older, more established medication, and is a little less expensive than its counterparts.

The most obvious sign that a medication dose is too strong is the onset of dehydration, which is characterized by thirst, fatigue, headaches, constipation, dizziness and headaches.

“Dehydration associated with renal failure and electrolyte abnormalities may occur with usage of loop diuretics since the medication is effective whether or not you need it,” Dr. Hsich says. “Therefore, it should be given with the advice of your medical provider and reduced or stopped during situations that cause dehydration like diarrhea, vomiting, and fevers.”

Hearing loss, though rare, can occur with high doses of sulfonamide loop diuretics, she adds. Allergies to these medications are also unusual, but they can appear, which is why it’s critically important to keep your physician apprised of any symptoms or side effects you experience after starting with a loop diuretic.

And be sure to understand what to expect when you start taking a loop diuretic. You maybe prescribed other drugs, such as beta blockers to help treat your heart failure and high blood pressure.

“Patients can remain on loop diuretics forever,” Dr. Hsich says.  “With time though, a patient may require a higher dose of the loop diuretic or a booster pill like a thiazide diuretic to establish the same diuretic effect they experienced ­earlier.”

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