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Sulfonamides are considered Bacterio________.
Static: They DO NOT KILL the bacteria, they stop the bacteria from proliferating
What are sulfonamides structually similar to?
Sulfonamides are often used _____________________ with other drugs.
What are the pros of synergism?
- lower concentration of drug used
- broader spectrum
- reduces drug resistance
What infection are sulfonamides most commonly used in treating?
How were sulfonamides fisrt discovered?
- Gerhard Domagk and bright red dye (Prontosil) in mice
- azo functional group was reduced in vivo
Why are there only about a dozen sulfonamides used worldwide instead of thousands?
- sulfonamide toxicity in some patients
- resistant bacterial strains because of early indiscriminant use
What are the risks of using an unprotected sulfonamide with a high pKa value?
- Form into sodium salt
- Becomes supersaturated n urine
- crystals begin to form (crystalluria)
How do you avoid chemically avoid crystalluria with sulfonamides?
- Attach heterocyclic rings to lower pKa (ionized-water soluble)
- Use more than one type of sulfonamide (amount of each does not reach threshold amt to form crystals)
What did earliest sulfonamides lead to crystallization and kidney damage?
- poor water solubility
- molecules were unionzed at urine pH
Sulfonamides are partially deactivated by __________________ & ___________________.
- (metabolized because of increased levels of enzyme---polarized and cleared quickly)
Because sulfonamides are similar to PABA they are considered a ____________________.
What is the mechanism of sulfonamides?
- competitive inhibitors of PABA
- prevent synthesis of Dihydrofolic acid
- inhibits mechanism of DNA synthesis
What is the mechanism of Folate Reductase Inhibitors (Trimethoprim)?
- Folate reductase inhibitor
- prevents synthesis of Tetrahydrofolic acid
Why may Trimethoprim cause side effects?
there is some affinity for human folate reductase
Why does the inhibtion of folate synthesis stop infection?
Microbes CANNOT use dietary folic acid
The blocking of two points in the folate pathway is called _______________________.
When is trimethoprim used clinically as a single agent?
oral treatment of uncomplicated UTIs
What is the fixed ratio of sulfamethoxazole to trimethoprim?
5 to 1
What are the 2 main reasons to use the combination of TMP-SMZ?
- synergistic in vitro
- less likely to induce bacterial resistance than either used alone
What enzyme does does sulfamethoxazole block?
What enzyme does trimethoprim block?
What are the 3 major indications for SMZ-TMP?
- Pneumocystic carinii pneumonia
- otitis media
In what patients should use caution with SMZ-TMP?
renal/ hepatic failure
What drugs action can increased due to the increased inhibition of hepatic metabolism by SMZ-TMP?
What substrates synthesis is inhibited by SMZ-TMP thus preventing DNA synthesis?
_________ are essential intermediates for synthesis of DNA bases.
Most susceptible bacteria to SMZ-TMP synthesize their own ____________.
What is the standard spectrum activity of SMZ-TMP?
- gram (-)
- H. influenza is becoming resistant (40-50%)
- some staph and strep coverage
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