Sulfonamides (Bactrim/Septra) (TMP/SMX)
- Sulfonamides are Folic Acid Antagonists
- TMP/SMX (1:5) Ratio
- Bactrim Tablet= (SMZ=400mg/TMP=80mg)
- Covers: wide spectrum, Gram+, most Gram-
- Shortage of IV formulation in U.S. so use PO if possible
- Used for: Community-acquired MRSA skin infections, UTI’s, Nocardiosis, Pneumonia, Sinusitis, Listeria infections, Salmonella infections, Traveler’s diarrhea, acute bronchitis, otitis media and more
- Sulfamethoxazole is combined with Trimethoprim (TMP/SMX) for its synergistic effect
- Sulfonamide allergy (Sulfa allergy) is common
- TMP/SMX should be used with caution in patients with impaired renal or liver function & patients with chronic folate deficiency
- Do not use in pregnant women because TMP/SMX may interfere with folic acid metabolism
- Patients should be instructed to drink one 8-ounce glass of water with each dose several times a day to prevent crystalluria
- Patients should avoid prolonged exposure to sunlight because photosensitivity may occur
- Sulfonamides increase INR in patients on Coumadin (Do not use with Coumadin)
- Sulfonamides remain a valuable low cost agent for patients
Side Effects
- Crystalline aggregates in urine
- Hepatitis
- Photosensitivity
- Bone Marrow Toxicity (Hemolytic Anemia)
- Steven-Johnson Syndrome (SJS)
- Increases serum creatinine levels
- Rash, GI irritation
- hyperkalemia
- hyperglycemia
- increases the effects of Coumadin & Phenytoin
- can cause hemolysis in glucose-6-phosphate dehydrogenase (G6PD)
Adult Dosage
Sulfonamides (Bactrim/Septra) (TMP/SMX)
- 1tab PO BID (DS, 160mg TMP/800mg SMX)
- For Travelers’ diarrhea 1tab PO BID DS x 5 days
- For Pneumocystis prophylaxis 1tab PO Daily
- Avoid use with coumadin
- Use renal dosage in renal dysfunction
Peds Dosage
Sulfonamides (Bactrim/Septra) (TMP/SMX)
- 1ml/kg/day sup PO divided two times per day (up to 20ml PO BID)
- A poor option for otitis media & sinusitis due to high pneumococcus & H influenza resistance rates
- Not effective for streptococcal pharyngitis
- unapproved for community acquired MRSA skin infections in children
♦These dosages are a guide only & must be rechecked♦
♦This information was obtained from Tarascan Pocket Pharmacopoeia 2014 Deluxe Lab-Coat Edition p. 89-90♦