Sulphonamide Antibacterial Agent

Drug Names
1. Code Name
2. Chemical Name
3. Generic/Non-Proprietary Name
4. Trade Name
Gram Test
1. Heteroaromatic purple stain mixed with bacteria
  1. Sticks to outer membrane
    1. Decolourisation with organic solvent
      1. Gram Positive: Purple
      2. Gram Negative: Red
Mode of Action
1. Prontosil
  1. Azodye
  2. Prodrug; reduced to sulphanilamide.
2. Prodrug
  1. Compound metabolised in vivo to active form of drug.
SAR
1. Para-Amino essential (primary!)
2. Aromatic Ring and Sulphonamide essential
3. Sulphonamide primary or secondary only
4. R' only modifiable.
Improved Sulpha Drugs
1. Sulphanilamide
  1. Poorly water soluble
  2. Toxic via crystallisation in kidneys
2. Second Generation
  1. Improved solubility via increased polarity
  2. pKa close to that of most of the body.
Site of Action
1. Dihydropterase Synthase
  1. Involved in folic acid biosynthesis
2. Folic Acid
  1. Essential for 1-Carbon unit transport of all oxidation states.
  2. Required for DNA synthesis.
Competitive Inhibitors
1. Sulphanilamide competes with PABA for dihydropterate synthase.
2. Bacterial DHFR different in structure than human's
  1. Trimethoprim - competitive inhibitor of DHFR
Septrin
1. Synergistic
2. Trimethoprim and Sulphamethoxazole
3. Example of: Anti-metabolite and Bacteriostatic Drug

Resource summary

	Created by Becky Harrison about 5 years ago