Sunday, 1 March 2015

COTRIMOXAZOLE

MECHANISM:
                    Cotrimoxazole is a combination of sulfamethaoxazole + trimethoprim in a ratio of 5:1 .
Sulfamethaoxazole and trimethoprim separately are bacteriostatic drugs but when combined together they become bacteriocidal .
Cotrimoxazole is a bacteriocidal drug.
Bacteriocidal activity is due to sequential blockade .
Sulfamethoxazole inhibit folate synthase and trimethoprim inhibits
folate reductase.  

PHARMACOKINETICS:

  1. Taken orally 
  2. Metabolized in liver
  3. Excreted in urine 
USE:
  1. UTI
  2. RTI
  3. MRSA
  4. Drug of choice for Pneumocystitis jirovecii and nocardiosis .
ADVERSE EFFECTS:
It has adverse effects of both sulphonamides and trimethoprim .

SULPHONAMIDE 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 SIDE 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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