What is the equivalency of ethacrynic acid to other loop diuretics like furosemide?

From the Guidelines

Ethacrynic acid is approximately equivalent to furosemide at a ratio of 50 mg ethacrynic acid to 40 mg furosemide, making ethacrynic acid slightly less potent on a milligram-to-milligram basis. When converting between these medications, a typical starting dose of ethacrynic acid is 50 mg orally once daily, which roughly corresponds to 40 mg of furosemide 1. Unlike other loop diuretics such as furosemide, bumetanide, and torsemide, ethacrynic acid has a unique chemical structure as a phenoxyacetic acid derivative rather than a sulfonamide. This makes ethacrynic acid the preferred loop diuretic for patients with sulfonamide allergies. However, ethacrynic acid tends to have more ototoxicity (hearing damage) and gastrointestinal side effects than other loop diuretics, so it's generally reserved for patients who cannot tolerate sulfonamide-based alternatives. For intravenous administration, 50 mg of ethacrynic acid is approximately equivalent to 40 mg of IV furosemide, 1 mg of bumetanide, or 20 mg of torsemide.

Some key points to consider when using ethacrynic acid include:

• The need for close monitoring of fluid status, electrolytes, and renal function when switching patients between loop diuretics, as individual response may vary 1
• The importance of adjusting the dose of diuretics based on patient response, with the goal of eliminating clinical evidence of fluid retention 1
• The potential for diuretic resistance, which can be overcome by the intravenous administration of diuretics, the use of 2 or more diuretics in combination, or the use of diuretics together with drugs that increase renal blood flow 1

It's also important to note that loop diuretics, including ethacrynic acid, increase sodium excretion up to 20% to 25% of the filtered load of sodium, enhance free water clearance, and maintain their efficacy unless renal function is severely impaired 1. In contrast, thiazide diuretics increase the fractional excretion of sodium to only 5% to 10% of the filtered load, tend to decrease free water clearance, and lose their effectiveness in patients with impaired renal function.

From the Research

Ethacrynic Acid Equivalency

• Ethacrynic acid is a loop diuretic that produces a prompt and profound diuresis, with its primary action being the inhibition of the Na⁺-K⁺-2Cl⁻ symporter in the thick ascending limb of the loop of Henle 2.
• The equivalency of ethacrynic acid to other loop diuretics like furosemide is not directly stated in the provided studies, but it is mentioned that ethacrynic acid can be effective for refractory congestive heart failure and ascites, especially in patients allergic to sulfa-containing drugs 3.
• A study comparing the pharmacokinetic profiles, comparative safety and efficacy, and comparative costs of loop diuretics found that torsemide may be more efficacious and safer than furosemide in patients with heart failure, but little evidence exists to support either torsemide or bumetanide as first-line treatment over furosemide in patients with other edematous disease states 4.
• The use of loop diuretics, including ethacrynic acid, in critical care medicine is reviewed, highlighting their combined venodilatory and natriuretic effects in relieving congestive symptoms in pulmonary edema 5.
• The studies suggest that ethacrynic acid can be an effective alternative to furosemide in certain cases, but its equivalency to furosemide is not explicitly stated 2, 3, 4, 5.

Comparison to Furosemide

• Ethacrynic acid has a prompt venous dilatory effect and can immediately relieve symptoms of pulmonary congestion, before a diuresis can occur 2.
• Furosemide, on the other hand, has a similar natriuretic potency to hydrochlorothiazide, and its effects can be compared to those of torsemide and bumetanide 6, 4.
• The choice of loop diuretic may depend on the specific clinical situation and patient characteristics, with ethacrynic acid being an option for patients who are allergic to sulfa-containing drugs or who have refractory congestive heart failure and ascites 2, 3.

Clinical Use

• Ethacrynic acid is effective in all types of edema, whether there is clinical acidosis, alkalosis, or electrolyte imbalance 2.
• Its use is limited by its side-effect profile, which includes ototoxicity and the potential for metabolic alkalosis 2.
• The studies suggest that ethacrynic acid can be a useful addition to the treatment of congestive heart failure and other edematous states, especially in patients who do not respond to other loop diuretics 3, 4.