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Sulphonamides

Sulphonamides. Antimicrobial drugs of synthetic origin Discovery of 1 st Sulphonamide in 1935 Domagk found that Prontosil dye inhibited the growth of streptococcal bacteria in mice Prontosil was found to contain Sulphanilamide and Domagk was awarded with Noble prize for his discovery.

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Sulphonamides

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  1. Sulphonamides Antimicrobial drugs of synthetic origin Discovery of 1st Sulphonamide in 1935 Domagk found that Prontosil dye inhibited the growth of streptococcal bacteria in mice Prontosil was found to contain Sulphanilamide and Domagk was awarded with Noble prize for his discovery

  2. Structure of Sulphonamides para-Aminobenzoic acid Sulphonamide

  3. Structure of Sulphonamides

  4. Mode of action of Sulphonamides

  5. Mode of action of Sulphonamides • Their basic structure resembles that of PABA • PABA is used by certain micro-organisms to synthesize Folic acid • Utilization of Sulphonamide (instead of PABA) depletes the micro-organisms of Folic acid • Inhibition of bacterial metabolism occurs

  6. Biotransformation • Major metabolic pathways: • Acetylation • Reduces the solubility of concerned drug • Half life is prolonged • Slow acetylators (dogs and other non-ruminants) • Fastacetylators (ruminants) • Glucoronide conjugation • Minor metabolic pathways: • Sulphate conjugation • Hydro-oxylation

  7. Therapeutic Uses of Sulphonamides Sulphacetamide Good penetration in eye Non-irritating Silver sulphadiazine Prevention and treatment of burn wound infections Available with the brand name of “Quench” cream Bacterial corneal infection

  8. Therapeutic Uses of Sulphonamides Sulphadoxine Serum half-life is measured in days rather than minutes or hours Combined with Pyrimethamine to treat malaria Plasmodium vivax

  9. Therapeutic Uses of Sulphonamides Urinary tract infections Nocardiosis: Sulphadiazine + Minocycline Coccidiosis Mastitis Metritis Nocardia asteroides

  10. Therapeutic Uses of Sulphonamides Toxoplasmosis

  11. Antagonists of Sulpha drugs • PABA • Folic acid • Thymine • Purine • Glycine • Pus and tissue debris • Procaine (precursor of PABA)

  12. Toxicity of Sulphonamides Crystallization in acid urine (Crystalluria) Common to uncommon depending on drug Alkalinize urine, increase hydration or use combination of Sulphonamides

  13. Sulfa crystals from the urinary sediment of a patient taking Sinomin (sulfamethoxazol). These crystals resemble crystals of uric acid or calcium oxalate, but sulfa crystals are soluble in acetone. Unstained, X400.

  14. Toxicity of Sulphonamides • Idiosyncratic hemolytic anemia • Occurs in Individuals with congenital deficiency of glucose-6 phosphate dehydrogenase • Inadequate level of glutathion (anti-oxidant in RBCS) • Hemolytic anemia caused by reactive oxygen species • May occur within 2-7 days of therapy

  15. Toxicity of Sulphonamides • Hypersensitivity reactions • Allergic skin reactions • Expoliative dermatitis • Cutaneous eruption • Reversible immune-mediated polyarthritis • Caused by Sulphadiazine • Affects dogs of Doberman breed

  16. Toxicity of Sulphonamides • Hypoprothrombinemia: • Prolonged administration of certain Sulphonamides (like Sulphaquinoxaline) • Inhibition of vitamin K epoxide reductase enzyme • Leads to vitamin K deficiency • Prolongation of bleeding and clotting times

  17. Toxicity of Sulphonamides • Keratoconjuctivitis sicca (KCS): • Caused by Sulpha drugs having nitrogen containing pyridine ring • Exerts lacrymotoxic effect • Characterized by hypolacrimation, dryness of eyes

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