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30 Cards in this Set

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