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22 Cards in this Set

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  • Back
What do sulfonamides do? How do they work?
They are antifolates
They block the enzyme that converts Pteridine and Dihydropteroic acid. This reaction is specific to bacteria
What is the enzyme in bacteria that converts pteridine + PABA into dihydropteroic acid?
Dihydropteroate synthase
What are the main mechanisms of bacterial resistance to sulfonamides?
Alteration of the enzyme to decrease affinity for drug
Increased production of PABA
What are two possible problems with the use of sulfonamides?
Widespread resistance
Bacteristatic, so they need the immune system to clear the bacteria
How are sulfonamides administered?
Orally
How are sulfonamides excreted?
Renally, achieve high concentrations in the urine
What are some adverse effects of sulfonamides?
Crystalline aggregates in urine
Acute hemolytic anemia (KNOW)
Hypersensitivity (Stevens-Johnson syndrome)
GI irritation
What presupposes someone to acute hemolytic anemia in response to sulfonamides?
G6PD deficiency, which is becoming more widespread
How do sulfonamides impact the use of some other drugs? Name one specific drug.
It inhibits CYP2C9, which metabolizes some drugs. One specific example is warfarin. This is dangerous because warfarin has a very narrow therapeutic range
What does trimethoprim do?
Antifolate that blocks the conversion of dihydrofolic acid to tetrahydrofolic acid
What enzyme does trimethoprim block?
Dihydrofolate reductase (DHFR)
Is trimethoprim bacteristatic or bactericidal?
Bacteristatic
What are the mechanisms of bacterial resistance to trimethoprim?
Increased production of DHFR
Alteration of DHFR to reduce binding
With what other drug does trimethoprim have a synergistic effect?
Sulfamethoxazole
What are some adverse effects of trimethoprim-sulfamethoxazole?
Higher incidence of dermatologic reactions
Folate-deficient patients may develop hematologic toxicities
Patients with AIDS have high incidence of adverse reactions
GI irritation
What are some clinical uses of trimethoprim-sulfamethoxazole?
Sensitive gram positive and gram negative organisms
UTIs (present in urine, unchanged)
Acute otitis media in children
PCP (pneumonia) in AIDS patients
How does linezolid work?
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
What are the mechanisms of bacterial resistance to linezolid?
Mutations in 23S that prevent binding of drug
Methylation of 23S that prevents binding - gives resistance to many other drugs
How is linezolid administered?
Orally
How is it excreted?
Renally, 30% as unchanged drug
What are some adverse effects of linezolid?
Headache
Hematologic toxicity
Serotonin toxicity (inhibition of monoamine oxidase)
Peripheral or optic neuropathy
What are the clinical uses of linezolid?
Serious infections:
VRE (vancomycin-resistant E. faecium)
MRSA