Sulfonamides

Most sulfonamides are readily absorbed orally and, when applied to burns, topically. Sulfonamides are distributed throughout the body. They are metabolized mainly by the liver and excreted by the kidneys. Sulfonamides compete for bilirubin-binding sites on albumin.

Sulfonamides are active against

Sulfasalazine can be used orally for inflammatory bowel disease Irritable Bowel Syndrome (IBS) Irritable bowel syndrome is characterized by recurrent abdominal discomfort or pain with at least two of the following characteristics: relation to defecation, association with a change in frequency... read more .

Sulfonamides are most commonly used with other drugs (eg, for nocardiosis Nocardiosis Nocardiosis is an acute or chronic, often disseminated, suppurative or granulomatous infection caused by various aerobic soil saprophytes of the gram-positive bacilli genus Nocardia.... read more , urinary tract infection Bacterial Urinary Tract Infections Bacterial urinary tract infections (UTIs) can involve the urethra, prostate, bladder, or kidneys. Symptoms may be absent or include urinary frequency, urgency, dysuria, lower abdominal pain... read more , and chloroquine-resistant falciparum malaria Treatment of Malaria in the United States ).

Topical sulfonamides can be used to treat the following:

Sulfonamides are contraindicated in patients who have had an allergic reaction to them or who have porphyria.

Sulfonamides do not eradicate group A streptococci in patients with pharyngitis and should not be used to treat group A streptococcal pharyngitis.

Evidence regarding an association between sulfonamides and birth defects is mixed. Animal studies with sulfonamides show some risk, and adequate studies have not been done in pregnant women.

Use near term and in breastfeeding mothers is contraindicated, as is use in patients < 2 months of age (except as adjunctive therapy with pyrimethamine to treat congenital toxoplasmosis). If used near term during pregnancy or in neonates, these drugs increase blood levels of unconjugated bilirubin and increase risk of kernicterus Kernicterus Kernicterus is brain damage caused by unconjugated bilirubin deposition in basal ganglia and brain stem nuclei. Normally, bilirubin bound to serum albumin stays in the intravascular space. However... read more in the fetus or neonate.

Sulfonamides enter breast milk.

Adverse effects of sulfonamides can result from oral and sometimes topical sulfonamides; effects include

Hypothyroidism, hepatitis, and activation of quiescent systemic lupus erythematosus may occur in patients taking sulfonamides. These drugs can exacerbate porphyrias.

Incidence of adverse effects is different for the various sulfonamides, but cross-sensitivity is common.

Sulfasalazine can reduce intestinal absorption of folate (folic acid). Thus, use of this drug may trigger folate deficiency in patients with inflammatory bowel disease, which also reduces absorption, especially if dietary intake is also inadequate.

Mafenide may cause metabolic acidosis by inhibiting carbonic anhydrase.

To avoid crystalluria, clinicians should hydrate patients well (eg, to produce a urinary output of 1200 to 1500 mL/day). Sulfonamides can be used in patients with renal insufficiency, but peak plasma levels should be measured and sulfamethoxazole levels should not exceed 120 mcg/mL.

Sulfonamides can potentiate sulfonylureas (with consequent hypoglycemia), phenytoin (with increased adverse effects), and coumarin anticoagulants.