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30 Cards in this Set
- Front
- Back
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What is the effect of Probenacid on UTI tx?
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inhibits OAT activity and thus, blocks the renal concentration of some drugs
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What do you us Probenacid for?
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Tx of gout
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Name 4 drugs that are general inhibitors of DNA replication to tx UTIs
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Cirofloxacin, Norfloxacin, Nalidixic Acid and Nitrofurantoin
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Name 4 drugs that are general inhibitors of the synthesis of folic acid leading to purine/pyrimidine synthesis defects in the tx of UTIs
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Sulfadoxine, Sulfamethoxazole, Sulfisoxizole, Trimethoprim
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Name the urinary tract antiseptics
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Nalidixic acid, Nitrofurantoin, Methenamine
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Name a drug to tx UTIs that has the same mechanism as fluoroquinolones
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Nalidixic Acid (Inhibit DNA replication by interfering with DNA gyrase and Topoisomerase IV)
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What accounts for Nitrofurantoin's selective toxicity?
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Bacteria reduce the drug to it's reactive intermediates much more rapidly than mammalian cells
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Why is Nitrofurantoin contraindicated in pts with impaired renal function?
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Due to inadequate urine concentrations and the danger of SE may be >
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Due to its limited resistance, what is a first line antiseptic to tx UTIs?
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Nitrofurantoin
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Is Nitrofurantoin bacteriostatic or bacteriocidal?
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Both. static at low levels, cidal at higher levels.
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What is important about the urine when using Methenamine?
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It must be acidic at a pH below 5.5 for it to be effective
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Why are Proteus orgs resistant to Methenamine?
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They are a urea-splitting organism that tend to raise the pH of the urine
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MOA of methenamine?
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Methanamine + Water = decomposes to formaldehyde and ammonia in an acidic environment
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Why is it not a concern that methenamine distributes widely into body fluids?
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Because the body fluids should have a pH of 7 that is not acidic enough for the drug to decompose into formaldehyde
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Can Methenamine be used to treat upper UTIs?
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No, there is inadequate time for generation of sufficient formaldehyde
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Glomerular filtration is proportional to what?
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creatinine clearance
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Css
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Drug concentration at steady state
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If clearance of a drug decreases, what must you do to maintain Css?
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Decrease dose and/or increase the interval (Maintenance dose/dosing interval = Css x Clearance)
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How do you measure duration of effective concentration (DEC?)
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Time spent above minimum inhibitory concentration (MIC)
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Fluroquinolones, conecentration or time dependent killing?
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Concentration dependent
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What dose is favored for concentration dependent killing?
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Single dose with a high peak concentration
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What dose is favored for time dependent killing?
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Multiple small doses
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What is the "post antibiotic effect?"
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Persistent suppression of bacterial growth after limited exposure to an antimicrobial agent
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Post antibiotic effect contributes to the efficacy of what sort of dosing?
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Once daily dosing
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What concentrates antibiotics in the urine?
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OAT
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What is the mechanism of Sulfamethoxazole?
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Synthetic analog of PABA; competitive inhibitor of dyhydropterorate synthatase (Blocks folate metabolism)
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What is the mechanism of Trimethoprim?
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Inhibits dihydrofolate reductase, blocking folate metatbolism
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What drug is contraindicated with the use of Methenamine and why?
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Sulfa drugs (cotrimoxazole too) b/c they react with the formaldehyde produced
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Why is methenamine contraindicated in pts with hepatic insufficiency?
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The liver metabolizes ammonia (byproduct of methenamine met) into urea
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What is the mechanism of Nitrofurantoin?
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reduced by bacteria to very active metabolites that damage bacterial DNA
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