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15 Cards in this Set
- Front
- Back
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What is the mechanism of action for sulfa drugs?
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Mimics PABA and inhibits dihydropteroate synthetase.
In some strains, sulfonamide can be processed by dihydropteroate synthetase into a false metabolite which inhibits DHF synthetase. |
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What is the SAR of sulfa drugs?
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Free Aniline group (benzyl amine) is required for enzyme binding and inhibition.
Ionized form binds to dihydropteroate synthetase. Unionized form penetrates bacteria cell membrane by diffusion. |
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What are the possible adverse reactions of sulfa drugs?
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Hypersensitivity
Kidney damage caused by crystalluria Hematological adverse effects GI discomfort and nausea |
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Low pKa favors
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Drug binding to dihydropteroate synthetase
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High pKa favors
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permeation through GI and bacterial cell membranes
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How can you reduce sulfa drug crystal formation in the kidney?
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Increase urine flow
Increase pH (sodium bicarb) Use sulfonamides with low pKa Mix different sulfonamides to achieve appropriate total dose. |
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Trisulfapyrimdine Oral suspension and tablets consist of...
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Sulfadiazine
Sulfamerazine Sulfamethazine |
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Triple Sulfa contains...
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Sulfabenzamide
Sulfacetamide Sulfathiazole |
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What is triple sulfa used for?
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Haemophilus vaginalis vaginitis
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What is the MOA of trimethoprim?
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Inhibition of bacterial DHFR, but not human DHFR
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How can resistance develop against Trimethoprim?
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Mutated DHFR with reduced affinity to Trimethoprim
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Which sulfa drug is used for ulcerative colitis? What does it break down to in the colon?
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Sulfasalazine
breaks down into 5-aminosalicylic acid and sulfapyridine. |
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What is sulfacetamide sodium used for?
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ophthalmic infections
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What is silver sulfadiazine used for?
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burn treatment
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How can resistance develop against sulfa drugs?
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1. Mutated dihydropteroate synthetase
2. Increased production of PABA 3. Decreased permeation/ increased efflux 4. Finding alternative ways to obtain folic acids or their precursors |
