What are the medications included in the sulfa drug list?

Sulfa Drug List

Sulfonamide Antibiotics

Sulfonamide antibiotics are a class of antimicrobial agents that share a common sulfonamide chemical structure and are primarily used for treating bacterial infections, particularly urinary tract infections, respiratory infections, and certain opportunistic infections. 1

Primary Sulfonamide Antibiotics

• Trimethoprim-sulfamethoxazole (TMP-SMX): Also known as co-trimoxazole or Bactrim/Septra, this is the most commonly used sulfonamide combination, containing both trimethoprim and sulfamethoxazole 1

• Sulfamethoxazole: The sulfonamide component of TMP-SMX, used in combination therapy 1

• Sulfisoxazole: A short-acting sulfonamide used primarily for urinary tract infections and otitis media, typically dosed at 120-150 mg/kg per day in 4 doses for children 1, 2

• Sulfadiazine: Used primarily for toxoplasmosis treatment, typically dosed at 500-1,000 mg four times daily in combination with pyrimethamine 1

• Sulfasalazine (salazosulfapyridine): Primarily used for inflammatory bowel disease (ulcerative colitis) rather than infections 1

Less Common Sulfonamides

• Sulfametrole: Combined with trimethoprim as an alternative to TMP-SMX, particularly when administered intravenously 3

• Dapsone: A sulfone antibiotic (structurally related to sulfonamides) used for Pneumocystis pneumonia prophylaxis, typically dosed at 50-100 mg daily 1

Clinical Applications by Indication

Urinary Tract Infections

• First-line: TMP-SMX (trimethoprim 5 mg/kg with sulfamethoxazole 30-60 mg/kg per day in 2 doses) for children 1
• Alternative: Sulfisoxazole 120-150 mg/kg per day in 4 doses 1

Pneumocystis Pneumonia Prophylaxis

• First-line: TMP-SMX 1 double-strength tablet daily or 1 single-strength tablet daily 1
• Alternative: Dapsone 50 mg twice daily or 100 mg daily 1

Toxoplasmosis Treatment

• Primary regimen: Sulfadiazine 500-1,000 mg four times daily plus pyrimethamine 25-50 mg daily plus leucovorin 10-25 mg daily 1

Plague Treatment

• Alternative agent: Trimethoprim-sulfamethoxazole 5 mg/kg (trimethoprim component) every 8 hours IV or PO for both adults and children 1

Nocardia Infections

• First-line: TMP-SMX remains the treatment of choice, with other sulfa antibiotics (sulfadiazine, sulfasoxazole) as effective alternatives 1

Important Safety Considerations

Contraindications and Warnings

• Pregnancy: Avoid trimethoprim in first trimester and sulfamethoxazole in last trimester due to risks of neural tube defects and kernicterus respectively 4, 5

• Renal function: Urinalyses with careful microscopic examination and renal function tests should be performed during therapy, particularly for patients with impaired renal function 5

• Hematologic monitoring: Complete blood counts should be done frequently; discontinue if significant reduction in any formed blood element occurs 5

• Fluid intake: Patients should maintain adequate fluid intake to prevent crystalluria and stone formation 5

Drug Interactions

• Warfarin: TMP-SMX may prolong prothrombin time; reassess coagulation time when used concurrently 5

• Phenytoin: TMP-SMX may inhibit hepatic metabolism of phenytoin, increasing phenytoin half-life by 39% 5

• Methotrexate: Sulfonamides can displace methotrexate from plasma protein binding sites and compete with renal transport, increasing free methotrexate concentrations 5

• Cyclosporine: Marked but reversible nephrotoxicity reported with coadministration in renal transplant recipients 5

• Oral hypoglycemics: TMP-SMX potentiates the effect of oral hypoglycemic agents 5

• ACE inhibitors: Three cases of hyperkalemia reported in elderly patients with concurrent use 5

Common Adverse Effects

• Gastrointestinal: Nausea, vomiting, abdominal pain, diarrhea (most frequent and dose-related) 2, 6

• Dermatologic: Rash, urticaria, photosensitivity, and rarely Stevens-Johnson syndrome or toxic epidermal necrolysis 2

• Hematologic: Rarely, anemia, thrombocytopenia, granulocytopenia, or agranulocytosis (most reactions develop within two weeks) 6

• Pseudomembranous colitis: Patients should contact their physician immediately if watery and bloody stools develop, even up to two months after the last dose 5, 2

Cross-Reactivity and Allergy Considerations

There is zero cross-reactivity between sulfonamide antibiotics and penicillins, cephalosporins, or any beta-lactam antibiotics, due to the absence of the aromatic amine group at the N4 position. 7

• All beta-lactams, fluoroquinolones, macrolides, clindamycin, and tetracyclines can be used safely in sulfa-allergic patients without cross-reactivity concerns 7

• Cross-reactivity between sulfa antibiotics and non-antibiotic sulfonamides (such as thiazide diuretics, furosemide, or sulfonylureas) is rare but can occasionally occur 8

• For patients with true sulfa antibiotic allergy requiring treatment for infections typically treated with TMP-SMX, alternative antibiotics should be selected based on the specific infection and local resistance patterns 7, 8