32.sulphonamides

Question 1

how many groups does the classification of sulphonamides have?

Answer 1

4
1.oral absorbable agents
2.oral non-absorbable
3.topical
4.combined

Question 2

which are the oral absorbable agents of sulphonamides

Answer 2

1. short acting
   -sulfisoxazole tab,500mg
2. medium
   -sulfamethoxazole
3. long acting
   -sulfadoxine

Question 3

which are the oral non-absorbable agents of suphonamides

Answer 3

sulfaguanidine - tab.500mg

Question 4

which are the topical agents of sulphonamides?

Answer 4

1.silver sulfadiazine - cream 1% 25g
2.sulfacetamide - collyr 10% 20ml

Question 5

which are the combined drugs of sulphonamides?

Answer 5

1.co-trimoxazole (sulfamethoxazole + trimetroprim) - tab.120,480mg
2.fansidar (sulfadoxine + pyrimethamine) - tab.525mg
3.sulfasalazine - tab.entersolv.500mg

Question 6

definition of sulphonamides

Answer 6

synthetic antimicrobial drugs, which are structural analogues of P-aminobenzoic acid

Question 7

how are sulfonamides absorbed?

Answer 7

1.good oral absorption
2.exception is sulfaguanidine - used for GI infection

Question 8

how are sulfonamides distributed?

Answer 8

1.through bodily fluids
2.penetrate well BBB and placental barrier
3.highly bound to plasma proteins - may displace other drugs from binding sites on serum albumin

Question 9

how are sulfonamides metabolized + excretion ?

Answer 9

1. in liver by acetylation
2. metabolites precipitate at normal or acidic ph and form crystalluria
3. urine excretion

Question 10

Mechanism of action of non-combined sulfonamides

Answer 10

1.inhibit the synthesis of tetra—hydrofolic acid, which is synthesized from PABA
SA are structural analogs to PABA and compete with it for the bacterial enzyme dihydrofolate synthetase
2.have a bacteriostatic action
3.broad spectrum of action
-gram - : enterobacteriacae, not P.aeruginosa
-gram + : straphylo, strepto, actinomyces, nocardia
-protozoa: toxoplasma gondii

Question 11

mechanism of action of combined SA
+ spectrum of action

Answer 11

1.cotrimoxazole inhibits 2 consequtive steps in formation of 4-hydrofolic acid
-sulfamethoxazole inhibits dihydrofolate synthetase
-trimethoprim inhibits dihydrofolate reductase
2.combined SA are bactericidal

Question 12

adverse drug reactions of SA

Answer 12

1.disbacteriosis
2.hypersensitivity reaction: angioedema, steven johnson
3.nephrotoxicity due to crystalluria - prevent by adequate hydration
4.thrombocytopenia, granulocytopenia
5.hemolytic anemia in patients with G6PD deficiency
6.kernicterus in neonates - compete with bilirubin for its binding sites

Question 13

drug interactions of Sulfonamides

Answer 13

1. increased effect of warfarin - increased bleeding risk
2. compete with antidiabetic drugs for their binding sites (sulfonylureas) - hypoglycemia risk
3. alkalization increases their excretion
4. local anesthetics with esther bond release PABA which decreases SA action