Which diuretic do you recommend for a hypertensive patient allergic to sulfonamides?
—Roch P. Col, MD, Phoenix

Spironolactone would be a first choice. Another alternative is the loop diuretic with the least cross-reactivity to the sulfonamides, ethacrynic acid. Bear in mind also that it is not clear that allergy to sulfonamides is associated with allergy specifically to thiazide diuretics. A recent report found that people who are allergic to sulfonamides are more likely to be allergic to any other drug, including thiazides, than people who are not allergic to sulfonamides (N Engl J Med. 2003;349:1628-1635). In other words, the allergy to sulfonamides is a marker for hypersensitivity to drugs in general and not a specific indicator of sensitivity to thiazides.

Thus, a history of allergic reaction to a sulfonamide is not an absolute contraindication to use of a thiazide. If the patient had a severe allergic reaction to a sulfonamide, however, I would be more reluctant to prescribe a thiazide.
—Samuel J. Mann, MD (113-4)

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