Sulfonamides (cont.)

Pharmacy Author:
Medical and Pharmacy Editor:

The increased metabolism (break-down and elimination) of cyclosporine by the liver caused by sulfonamides (reduces the effectiveness of cyclosporine and can add to the kidney damage caused by cyclosporine.

All sulfonamides can crystallize in the urine when the urine is acidic. Since methenamine (Hiprex, Urex, Mandelamine) causes acidic urine, it should not be used with sulfonamides.

Blood levels of digoxin may increase blood levels of digoxin (Lanoxin) and possibly lead to serious toxic effects.

Anemia, due to a reduction in folic acid, can occur in persons receiving sulfonamides in combination with divalproex, valproic acid (Depakote, Depakote ER, Depakene, Depacon, Stavzor), methotrexate (Rheumatrex, Trexall), pyrimethamine, triamterene, or trimetrexate.

Increased blood levels of potassium may occur when sulfamethoxazole/trimethoprim is combined with angiotensin converting enzyme (ACE) inhibitors.

What formulations are sulfonamides are available?

Sulfonamides are available as tablets, injections, and oral solutions.

What about taking sulfonamides during pregnancy or while breastfeeding?

Use of sulfonamides may cause bilirubin to be displaced from proteins in the infant's blood. Displacement of bilirubin can lead to jaundice and a dangerous condition called kernicterus in the infant. For this reason, sulfamethoxazole/ trimethoprim should not be used near term (late in pregnancy) among women. Sulfonamides (for example, sulfamethoxazole/trimethoprim) should not be used by nursing mothers because sulfamethoxazole is excreted in breast milk and can cause kernicterus.

REFERENCE: FDA prescribing information.


Medically Reviewed by a Doctor on 3/3/2014


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