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Edecrin (Ethacrynic Acid) - Description and Clinical Pharmacology

 
 



EDECRIN [Registered trademark of ATON PHARMA, INC.
COPYRIGHT © 2007 ATON PHARMA, INC.
All rights reserved]
(Ethacrynic Acid) is a potent diuretic which, if given in excessive amounts, may lead to profound diuresis with water and electrolyte depletion. Therefore, careful medical supervision is required, and dose and dose schedule must be adjusted to the individual patient's needs (see DOSAGE AND ADMINISTRATION).

DESCRIPTION

Ethacrynic acid is an unsaturated ketone derivative of an aryloxyacetic acid. It is designated chemically as [2,3-dichloro-4-(2-methylene-1-oxobutyl)phenoxy] acetic acid, and has a molecular weight of 303.14. Ethacrynic acid is a white, or practically white, crystalline powder, very slightly soluble in water, but soluble in most organic solvents such as alcohols, chloroform, and benzene. Its empirical formula is C13H12Cl2O4 and its structural formula is:

Ethacrynate sodium, the sodium salt of ethacrynic acid, is soluble in water at 25°C to the extent of about 7 percent. Solutions of the sodium salt are relatively stable at about pH 7 at room temperature for short periods, but as the pH or temperature increases the solutions are less stable. The molecular weight of ethacrynate sodium is 325.12. Its empirical formula is C13H11Cl2NaO4 and its structural formula is:

EDECRIN is supplied as 25 mg tablets for oral use. The tablets contain the following inactive ingredients: colloidal silicon dioxide, lactose, magnesium stearate, starch and talc. Intravenous SODIUM EDECRIN (Ethacrynate Sodium) is a sterile freeze-dried powder and is supplied in a vial containing:

Ethacrynate sodium equivalent to ethacrynic acid...... 50.0 mg

Inactive ingredient:

Mannitol......................62.5 mg

CLINICAL PHARMACOLOGY

Pharmacokinetics and Metabolism

EDECRIN acts on the ascending limb of the loop of Henle and on the proximal and distal tubules. Urinary output is usually dose dependent and related to the magnitude of fluid accumulation. Water and electrolyte excretion may be increased several times over that observed with thiazide diuretics, since EDECRIN inhibits reabsorption of a much greater proportion of filtered sodium than most other diuretic agents. Therefore, EDECRIN is effective in many patients who have significant degrees of renal insufficiency (see WARNINGS concerning deafness). EDECRIN has little or no effect on glomerular filtration or on renal blood flow, except following pronounced reductions in plasma volume when associated with rapid diuresis.

The electrolyte excretion pattern of ethacrynic acid varies from that of the thiazides and mercurial diuretics. Initial sodium and chloride excretion is usually substantial and chloride loss exceeds that of sodium. With prolonged administration, chloride excretion declines, and potassium and hydrogen ion excretion may increase. EDECRIN is effective whether or not there is clinical acidosis or alkalosis.

Although EDECRIN, in carefully controlled studies in animals and experimental subjects, produces a more favorable sodium/potassium excretion ratio than the thiazides, in patients with increased diuresis excessive amounts of potassium may be excreted.

Onset of action is rapid, usually within 30 minutes after an oral dose of EDECRIN or within 5 minutes after an intravenous injection of SODIUM EDECRIN. After oral use, diuresis peaks in about 2 hours and lasts about 6 to 8 hours.

The sulfhydryl binding propensity of ethacrynic acid differs somewhat from that of the organomercurials. Its mode of action is not by carbonic anhydrase inhibition.

Ethacrynic acid does not cross the blood-brain barrier.

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