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22 Cards in this Set
- Front
- Back
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What do sulfonamides do? How do they work?
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They are antifolates
They block the enzyme that converts Pteridine and Dihydropteroic acid. This reaction is specific to bacteria |
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What is the enzyme in bacteria that converts pteridine + PABA into dihydropteroic acid?
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Dihydropteroate synthase
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What are the main mechanisms of bacterial resistance to sulfonamides?
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Alteration of the enzyme to decrease affinity for drug
Increased production of PABA |
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What are two possible problems with the use of sulfonamides?
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Widespread resistance
Bacteristatic, so they need the immune system to clear the bacteria |
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How are sulfonamides administered?
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Orally
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How are sulfonamides excreted?
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Renally, achieve high concentrations in the urine
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What are some adverse effects of sulfonamides?
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Crystalline aggregates in urine
Acute hemolytic anemia (KNOW) Hypersensitivity (Stevens-Johnson syndrome) GI irritation |
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What presupposes someone to acute hemolytic anemia in response to sulfonamides?
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G6PD deficiency, which is becoming more widespread
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How do sulfonamides impact the use of some other drugs? Name one specific drug.
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It inhibits CYP2C9, which metabolizes some drugs. One specific example is warfarin. This is dangerous because warfarin has a very narrow therapeutic range
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What does trimethoprim do?
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Antifolate that blocks the conversion of dihydrofolic acid to tetrahydrofolic acid
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What enzyme does trimethoprim block?
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Dihydrofolate reductase (DHFR)
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Is trimethoprim bacteristatic or bactericidal?
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Bacteristatic
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What are the mechanisms of bacterial resistance to trimethoprim?
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Increased production of DHFR
Alteration of DHFR to reduce binding |
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With what other drug does trimethoprim have a synergistic effect?
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Sulfamethoxazole
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What are some adverse effects of trimethoprim-sulfamethoxazole?
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Higher incidence of dermatologic reactions
Folate-deficient patients may develop hematologic toxicities Patients with AIDS have high incidence of adverse reactions GI irritation |
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What are some clinical uses of trimethoprim-sulfamethoxazole?
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Sensitive gram positive and gram negative organisms
UTIs (present in urine, unchanged) Acute otitis media in children PCP (pneumonia) in AIDS patients |
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How does linezolid work?
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It binds to the 23S subunit of the bacterial ribosome (23S is a subunit of 50S) and blocks the formation of the initiation complex. No protein translation
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What are the mechanisms of bacterial resistance to linezolid?
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Mutations in 23S that prevent binding of drug
Methylation of 23S that prevents binding - gives resistance to many other drugs |
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How is linezolid administered?
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Orally
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How is it excreted?
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Renally, 30% as unchanged drug
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What are some adverse effects of linezolid?
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Headache
Hematologic toxicity Serotonin toxicity (inhibition of monoamine oxidase) Peripheral or optic neuropathy |
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What are the clinical uses of linezolid?
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Serious infections:
VRE (vancomycin-resistant E. faecium) MRSA |
