Saturday, 28 February 2015


                         Sulphonamide inhibits folate synthase enzyme . Thus bacteria cannot synthesize the folic acid required for its growth . 
This drug does not affect the folic acid level in humans , because humans acquire folic acid directly from food and it's not synthesized.

Short acting : Sulfisoxazole
Intermediate acting : Sulfadiazine , Sulfamethaoxazole
Long acting : Sulfadoxime
For use in GIT : Sulfasalazine
For topical use : Sulfacetamide, Silver Sulfadiazine


  1. Taken orally 
  2. Metabolized in liver by acetylation
  3. Crosses placenta and Blood Brain Barrier
  4. Excreted in urine

  1. Sulfisoxazole used in UTI
  2. Sulfadiazine used in nocardiasis 
  3. Sulfadiazine + Pyrimethamine used for Toxoplasmosis and as prophylaxis of Pneumocystitis jiroveci
  4. Sulfadoxime + Pyrimethamine used in malaria .
  5. Sulfasalazine is used in Ulcerative colitis .
  6. Sulfacetamide is used for Ocular infections
  7. Silver sulfadiazine is used in burns patients .
Adverse Effects:
  1. Aplastic Anemia 
  2. Bilirubin displacement from plasma protein leading to Kernicterus
  3. Crystalluria
  4. Rash 
  5. SLE
  6. Hemolysis in patients with G-6PD deficiency 
                      mnemonic : ABC RAsH

                         These drugs inhibit Folate reductase enzyme , thus inhibiting the synthesis of THFA required for survival of bacteria . 
It is specific for bacterial folate reductase enzyme and has no effects on humans .


  1. Given orally
  2. Metabolized in liver
  3. Excreted in urine
  1. It is combined with sulphnomides and used widely.
  2. Used alone in UTI and Prostitis .
Adverse Effects:
  1. Megaloblastic Anemia
  2. Leukopenia
  3. Pancytopenia
  4. Hyperkalemia ( due to amiloride like action , amiloride is a Potassium sparing diuretic ).


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