Ethacrynic acid

Etacrynic acid (INN) or ethacrynic acid (USAN), trade name Edecrin, is a loop diuretic used to treat high blood pressure and the swelling caused by diseases like congestive heart failure, liver failure, and kidney failure.

Unlike the other loop diuretics, etacrynic acid is not a sulfonamide and thus, its use is not contraindicated in those with sulfa allergies.

Etacrynic acid is a phenoxyacetic acid derivative containing a ketone group and a methylene group. A cysteine adduct is formed with the methylene group and this is the active form.

Administration
Ethacrynic acid is sold in 25 mg and 50 mg tablets for oral use. The sodium salt (ethacrynate sodium) can also be given intravenously. The IV solution must be prepared and maintained with a pH above 5.

Adverse effects
As a diuretic, ethacrynic acid can cause frequent urination, but this usually resolves after taking the drug for a few weeks.

Ethacrynic acid can also cause low potassium levels, which may manifest as muscle cramps or weakness. It has also been known to cause reversible or permanent hearing loss (ototoxicity) and liver damage. On oral administration, it produces diarrhea; intestinal bleeding may occur at higher doses.

Mechanism of action
Ethacrynic acid acts by inhibiting sodium-potassium-chloride cotransport in the ascending loop of Henle. Loss of potassium ions is less marked but chances of hypochloremic alkalosis are greater. The dose response curve of ethacrynic acid is steeper than that of furosemide and, in general, it is less manageable; dose range is 50-150mg.

Ethacrynic acid and its glutathione-adduct are potent inhibitors of glutathione S-transferase family members, which are enzymes involved in xenobiotic metabolism. This family of enzymes has recently been shown to have a high rate of genetic variability.