Drug Interactions:
Loop Diuretics

These powerful diuretics are used to reduce fluid accumulation in the body.

Drugs in this family include bumetanide (Bumex), ethacrynic acid (Edecrin), furosemide (Lasix), and torsemide (Demadex) among others.

Potassium

Probable Need for Supplementation

Loop diuretics cause a constant and significant loss of potassium. The classic treatment for this is to eat bananas and drink orange juice. Potassium supplements are also frequently prescribed.

Magnesium

Probable Need for Supplementation

Long-term use (more than 6 months) of loop diuretics might lead to magnesium deficiency.^1,2,3 In turn, magnesium depletion can increase loss of potassium.⁴

Since magnesium deficiency is common anyway, taking a magnesium supplement at standard U.S. Dietary Reference Intake (formerly known as the Recommended Dietary Allowance) levels might make sense.

Vitamin B1

Probable Need for Supplementation

Evidence suggests that loop diuretics interfere with the body’s metabolism of vitamin B₁ (thiamin).^5,9,10

This effect may cause adverse consequences in one group of individuals who commonly take loop diuretics: people with heart failure. The heart depends on B₁ for proper function; therefore, this finding suggests that taking a B₁ supplement may be advisable. In fact, preliminary evidence suggests that thiamin supplementation does indeed improve heart function in individuals with congestive heart failure (CHF).^6,7,11

Licorice

Possible Dangerous Interaction

Licorice, too, affects potassium, and the combination of licorice and loop diuretics might cause unexpectedly rapid potassium loss.⁸ However, the special form of licorice known as DGL (deglycyrrhizinated licorice) should not affect potassium levels.

Dong Quai, St. John's Wort

Possible Harmful Interaction

Loop diuretics have been reported to cause increased sensitivity to the sun, amplifying the risk of sunburn or skin rash. Because St. John's wort and dong quai may also cause this problem, taking these herbal supplements during treatment with loop diuretics might add to this risk.

It may be a good idea to wear a sunscreen or protective clothing during sun exposure if you take one of these herbs while using a loop diuretic.

Last reviewed August 2002 by Medical Review Board

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