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16 Cards in this Set
- Front
- Back
What is the target for antimetabolites.
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Folic acid pathway. Folic acid is a methyl donor. Bacteria make their own and don't like exogenous folic acid like we do.
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Dihydropteroate synthase
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Carries out first step of folic acid synthesis.
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Dihydrofolate reductase
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Converts dihydrofolic acid to tetrahydrofolic acid.
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Sulfonamides
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Inhibit dihydropteroate synthase. They are competitive inhibitors. Many organisms now resistant through normal means. Must deplete intracellular stores of products before you see results.
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Sulfisoxazole
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Short-acting sulfonamide. Quickly sent through kidney in high amounts that are active. Makes it useful to initially treat uncomplicated UTI.
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Sulfamethoxazole
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Intermediate acting.
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Sulfacetamide use
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Sulfa drug for conjunctivitis.
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Silver sulfadiazine
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Prevent colonization in burns. Some or all activity could be due to silver ions.
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Trimethoprim
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Blocks dihydrofolate reductase. This pathway is common in all organisms and not just bacteria. Also used for UTI's but with combo of a sulfonamide (sequential blockade).
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Sulfonamide adverse side effects
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Affects skin mostly. Stevens-Johnson syndrome. Kernicterus. Crystalluria with older sulfonamides.
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Trimethoprim side effect
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Interfere with folate metabolism in malnourised individuals like alcoholc, megaloblastic anemia, leukopenia, granulocytopenia.
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Urinary Tract Antiseptics (not technically antimetabolites but work similarly)
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Not intended for systemic effect. Rapidly excreted and highly protein bound. Any antibacterial that is excreted in the urine in an active form can be used to treat a UTI if the pathogen is susceptible to the drug. (TMP/SMZ, fluro, imipenem with cilistatin)
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Nitrofurantoin
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MOA poorly understood. Reduction of nitro gorup by bacteria to free radical that affects multiple systems. Most E. coli susceptible. Many gm- resistant. Rapidly secreted. Use for acute cystitis, UTI prophylaxis but NOT pyelonephritis
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Nitrofurantoin adverse affects
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N/V. Macrocrystalline as opposed to micro gives lower occurrence. Pulonary fibrosis.
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Methenamine
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Decomposes at acid pH. Mixture of formaldehyde and ammonia. Not for treatmean of cystitis but Used for prophylaxis of cystitis.
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Fosfomycin
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Inhibits cell wall synthesis at an early stage. Inhibits enzyme that makes muramic acid. Used only for cystitis. Single dose treatment that is equal for 7 days of other drugs.
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