Inhibition of Nucleic Acid Synthesis

Question 0

Sulfisoxazole

Answer 0

• Bacteriostatic sulfonamide
• MOA: PABA antimetabolites inhibit dihydropteroate synthase
• Use: gram +, gram -, Nocardia, Chlamydia
  
  1. Triple sulfas or SMX for simple UTI
• Toxicity:
  
  1. Hypersensitivity rxn
  2. Hemolysis if G6PD deficient
  3. Nephrotoxicity
  4. Photosensitivity
  5. Kernicterus in infants
  6. Displace other drugs from albumin
• Resistance:
  
  1. Altered enzyme (bacterial dihydropteroate synthase)
  2. Decreased uptake
  3. Increased PABA synthesis

Question 1

Sulfamethoxazole (SMX)

Answer 1

• Bacteriostatic sulfonamide
• MOA: PABA antimetabolites inhibit dihydropteroate synthase
• Use: gram +, gram -, Nocardia, Chlamydia
  
  1. Triple sulfas or SMX for simple UTI
• Toxicity:
  
  1. Hypersensitivity rxn
  2. Hemolysis if G6PD deficient
  3. Nephrotoxicity
  4. Photosensitivity
  5. Kernicterus in infants
  6. Displace other drugs from albumin
• Resistance:
  
  1. Altered enzyme (bacterial dihydropteroate synthase)
  2. Decreased uptake
  3. Increased PABA synthesis

Question 2

Sulfadiazine

Answer 2

• Bacteriostatic sulfonamide
• MOA: PABA antimetabolites inhibit dihydropteroate synthase
• Use: gram +, gram -, Nocardia, Chlamydia
  
  1. Triple sulfas or SMX for simple UTI
• Toxicity:
  
  1. Hypersensitivity rxn
  2. Hemolysis if G6PD deficient
  3. Nephrotoxicity
  4. Photosensitivity
  5. Kernicterus in infants
  6. Displace other drugs from albumin
• Resistance:
  
  1. Altered enzyme (bacterial dihydropteroate synthase)
  2. Decreased uptake
  3. Increased PABA synthesis

Question 3

Trimethoprim

Answer 3

• Bacteriostatic inhibitor of nucleic acid synthesis
• MOA: Inhibits bacterial dihydrofolate reductase
• Use: used in combo with sulfonamides (TMP-SMX)
  
  1. Sequential block of folate synthesis
  2. Combo for UTI, Shigella, Salmonella, Pneumocystis jiroveci
• Toxicity: Megaloblastic anemia, leukopenia, granulocytopenia
  
  1. May alleviate w/ supplement folinic acid