1. Mechanism of Action
    Interfere with bacterial synthesis of folic acid which leads to a decrease in tetrahydrofolic acid which is necessary for purine, thymidine and DNA synthesis.
  2. Absorption
    Good oral bioavailablity
  3. Sulfisoxazole
    • Short Acting
    • QID
    • Used to treat Otitis Media and sometimes UTIs (good urine solubility)
  4. Sulfadiazine
    • Short Acting
    • Passes into CSF due to minimal protein binding
    • Used in combination to treat nocardial infections and toxoplasmosis.
    • Low urine solubility
  5. Sulfamethoxazole
    • Intermediate Acting
    • Less solube in urine & slower excretion then sulfisoxazole
    • BID
    • Combined with trimethoprim for synergistic bactericidal effect.
  6. Sulfacetamide
    • Ophthalmic preparation used to treat superficial infections of the eye.
    • Doesn't penetrate systemically well due to PK.
  7. Mafenide
    • Broad Spectrum topical sulfa
    • Used primarily in burn patents
    • Effective against Pseudomonas
    • Diffuses well through devascularized areas.
    • Mafenide and it's metabolite are carbonic anhydrase inhibitiors. (Used with caution in patient with renal or pulmonary insufficiencies)
    • Adverse effects: Hypersensitivity, fungal colonization, local pain, and burning sensation.
  8. Silver Sulfadiazine
    • Tropical Sulfa used in burn patients
    • Effective against pseudomonas
    • Less pain than with mafenide and few applications needed
    • Sulfadiazine is absorbed & high concentrations can be achieved.
    • Crystaluria can be a problem.
  9. Sulfasalazine
    • Combination of a sulfa and antiinflammatory agent.
    • Used in treatment of IBD
    • Poor absorbed from GI tract
    • Metabolized by bacteria to sulfapyridine and 5-aminosalicylic acid.
  10. Trimethoprim-Sulfamethoxazole (Bactrim)
    Mechanism of Action
    • TMP-SMX
    • Combines two agents that inhibits bacteria synthesis at two sequential steps.
    • Bactericidal-synergistic activity
    • Slow development of resistance
  11. Trimethoprim-Sulfamethoxazole (Bactrim)-Mechanisms of Resistance
    • Increased production of PABA
    • Synthesis of altered enzymes
    • Increased production of dihydropteroate synthetase
    • Reduced Drug uptake
  12. Trimethoprim-Sulfamethoxazole (Bactrim) - Dosing
    • Optimal synergistic ratio of serum conc. is 1:20.
    • Achieved by a fixed dose ratio of 1:5.
  13. Trimethoprim-Sulfamethoxazole (Bactrim) - Spectrum of Activity
    • Gram Positive - MSSA, MRSA, S. epidermidis, S. pneumoniae.
    • Gram Negative - Most enterobacteriaceae, H. flu, M. catarrhalis, Salmonella, Shigella
    • Not active againist Pseudomonas and poor anaerobic coverage.
Card Set
Sulfonamide Drugs