Saturday, 28 February 2015

SULPHONAMIDE , TRIMETHOPRIM

SULPHONAMIDE:
MECHANISM:
                         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.

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

Pharmacokinetics:

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

  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


TRIMETHOPRIM:
MECHANISM:
                         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 .

PHARMACOKINETICS:

  1. Given orally
  2. Metabolized in liver
  3. Excreted in urine
USE:
  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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