Present indications for sulfonamides are outlined below.
A. Urinary Tract Infections
Coliform bacteria, the most common cause of urinary tract infections, are moderately inhibited by sulfonamides. However, resistance of E coli to sulfonamides is common and IDSA cautions against using them in communities with high (ie, greater than 20%) rates of resistance. Since trimethoprim is concentrated in the prostate, trimethoprim-sulfamethoxazole, one double-strength tablet twice daily for 14–21 days, is effective in acute prostatitis. In chronic prostatitis, treatment for 6–12 weeks is indicated.
Trimethoprim-sulfamethoxazole is effective for prophylaxis and treatment of pneumonia due to Pneumocystis jirovecii and treatment of Cyclospora infection and Cystoisospora belli infection. For therapy of Pneumocystis pneumonia, 15 mg/kg/day of trimethoprim (with the associated 75 mg/kg/day of sulfamethoxazole) in three or four divided doses is administered intravenously or orally—depending on the severity of disease—for 3 weeks. The dose for prophylaxis is 160 mg of trimethoprim plus 800 mg of sulfamethoxazole daily or three times per week. (When given daily, it is also effective prophylaxis against toxoplasmal encephalitis.) C belli infection in HIV/AIDS has been successfully treated with 160 mg of trimethoprim plus 800 mg of sulfamethoxazole orally four times daily for 10 days followed by twice-daily administration for 3 weeks. Cyclosporiasis is successfully treated with 160 mg of trimethoprim and 800 mg of sulfamethoxazole twice daily for 7–10 days. Sulfadiazine with pyrimethamine is also used to treat and prevent recurrence of toxoplasmosis.
C. Other Bacterial Infections
Considering the increased observation of CA-MRSA, trimethoprim-sulfamethoxazole is useful in the outpatient treatment of this organism. Epidemiologic evaluations demonstrate that antibacterials often have only a modest role in the treatment of skin and soft-tissue infection due to CA-MRSA. Nonetheless, trimethoprim-sulfamethoxazole is associated with a high cure rate among patients with a drained cutaneous abscess.
Sulfonamides are the medications of choice for Nocardia infections. Trimethoprim-sulfamethoxazole is widely distributed in tissues, penetrates into the cerebrospinal fluid, and has been used to treat meningitis caused by gram-negative rods, although third-generation cephalosporins have greater clinical experience and are preferred.
Trimethoprim-sulfamethoxazole is also effective for infections with Enterobacter, B pseudomallei (melioidosis), S maltophilia, or B cepacia; in combination with rifampin for eradication of nasopharyngeal carriage of staphylococci; for Pneumocystis prophylaxis in organ and stem cell transplant recipients and HIV/AIDS patients with CD4 counts less than 200 cells/mcL; and as an option for treatment of L monocytogenes meningitis.
Certain sulfones are widely used (see below).