Pharm- Antibiotics Antimetabolites

Front 1

What is the target for antimetabolites.

Back 1

Folic acid pathway. Folic acid is a methyl donor. Bacteria make their own and don't like exogenous folic acid like we do.

Front 2

Dihydropteroate synthase

Back 2

Carries out first step of folic acid synthesis.

Front 3

Dihydrofolate reductase

Back 3

Converts dihydrofolic acid to tetrahydrofolic acid.

Front 4

Sulfonamides

Back 4

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

Back 7

Sulfa drug for conjunctivitis.

Front 8

Silver sulfadiazine

Back 8

Prevent colonization in burns. Some or all activity could be due to silver ions.

Front 9

Trimethoprim

Back 9

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)

Back 12

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)

Front 13

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.