Medicinal chemistry Sulfonamides

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Well discussed classification, mechanism of action, structures

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Sulphonamides:

Sulphonamides Prepared by Mr. Dharmendrasinh A Baria Assistant professor Department of Pharmaceutical Chemistry Smt. S. M. Shah Pharmacy college, Amsaran 1

Description:

Description One of the oldest antibacterial agents used to combat infection Used for coccal infection in 1935 They are bacteriostatic because it inhibits bacterial synthesis of folic acid Clinical usefulness has decreased because of the effectiveness of other antibiotics and penicillin 2

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Presence of free amino group Antibacterial action Prontosil red Prodrug In vitro Inactive In vivo Active 3

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Chemical modification of the sulphonamide structure has given rise to several important group of drugs. Gloucoma – Acetazolamide Diuretic – Thiazides Anti- mycobacterial – Sulphones Oral hypoglycemic – Sulphonyl ureas 4

Mechanism of action:

Mechanism of action Competitive inhibitor to dihydropteroate synthase enzyme due to resemblance with para-amino benzoic acid. Sulfonamides therefore are reversible inhibitors of folic acid synthesis and bacteriostatic not bactericidal. Inhibit bacterial growth without affecting normal cells 5

Mechanism of action:

Mechanism of action 6

Antibacterial activity :

Antibacterial activity Gram-positive and gram negative. Nocardia , chlamydia trachomatis , some protozoa. Classification A. Sulphonamides employed for treatment of systemic infection. Depending upon duration , they can be further subdivided into 7

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a) Short to intermediate acting sulphonamides. 8

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B. Long acting sulphonamides C. Extra long acting sulphonamides 9

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2. Poorly absorbed sulphonamides 3. Topically used sulphonamides 10

Structure activity relationship:

Structure activity relationship General 1. Sulphonamide skeleton is the minimum structural requirement for antibacterial activity. 2. The active form of sulphonamide is the ionized form. Maximum activity is observed bretween the pk a value 6.6-7.4. 3. Sulphonamides competes for binding site on plasma albumin with causes increased action of drugs like Aspirin, Phenylbutazone , methotrexate etc. 11

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Therapeutic uses:

Therapeutic uses Urinary tract infections Upper respiratory tract infections Nocardiosis Sulfasalazine in IBD. Sulfacetamide in bacterial conjunctivitis & trachoma Silver sulfadiazine for prevention of infection of burn wounds . 13

Adverse effects:

Adverse effects Hypersensitivity reactions Crystalluria,hematuria,renal obstruction. Allergic nephritis Haemolytic anaemia, aplastic anaemia, thrombocytopenia. Kernicterus in new born 14

Trimethoprim - Sulfamethoxazole combination (Co-trimoxazole):

Trimethoprim - Sulfamethoxazole combination (Co- trimoxazole ) 15

Mechanism of action::

Mechanism of action: Sequential blocking of purine synthesis (synergism). Trimethoprim inhibits dihydrofolate reductase enzyme so inhibits tetrahydrofolic acid synthesis The combination is bactericidal 16

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Clinical uses:

Clinical uses Acute or Complicated or recurrent urinary tract infections especially in females Upper respiratory tract infections Pneumocystis jiroveci pneumonia Toxoplasmosis Shigellosis Nocardiosis 18

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Typhoid fever Salmonella infections Prostatitis Community –acquried bacterial pneumonia Clinical uses continues………….. 19

Adverse effects:

Adverse effects Megaloblastic anemia, leukopenia & granulocytopenia (can be prevented by administration of folic acid ) All side effects associated with sulfonamides 20

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