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Sulf/FQN/Furantin
Lecture 10
22
Pharmacology
Professional
02/02/2013

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Cards

Term
What is the MoA of sulfonamides?
Definition
Competition with PABA for synthase, inhibiting the synthesis of folic acid OR makes false metabolite
**Resistance: make more PABA or folic acid uptake from environment
Term
What is the MoA of trimethoprim?
Definition
Inhibits the 2nd step of the PABA pathway by inhibiting reductase
**Binds away from active site - selective for bacteria
Term
How does sulfa antibiotic resistance occur?
Definition
- Lower affinity for synthase
- PABA synthesis increases, salvage pathways
Term
How does ionization affect sulfonamide metabolism?
Definition
The ionized form is the active form - must be in a pKa lower than it (10.5)
Term
What is the biggest AE of sulfonamides?
Definition
crystal urea! Comes from unionized form in the urine. Drink LOTS of water
**Get out of the kidney by reducing the pKA/more basic - sodium bicarb
Term
How is sulfadiazine different from it's parent?
Definition
The pKa is lower, so it is more ionized at the body's pH and in the urine. Less concentration needed for an effect.
Term
What is triple sulfa used for?
Definition
Sulfadiazine/Sulfamerazine/Sulfamethazine
For UTI (gram -), dosed with Na-bicarb to increase ionization
Term
What is Silvadene?
Definition
Silver sulfadiazene/Silvadene inhibits growth when used topically - for burns
Term
What agents are sulfa antibiotics?
Definition
- Sulfisoxazole/Gantrisin - UTI and otitis media
- Sulfisoxazole and Phenazopyradine/ Azo-gantrisin
- Sulfisoxazole Acetyl/Pediazole - combo w/ E.E.S
- Sulfamethoxazole/Gantanol - does not cover MRSA by itself. Broad spectrum
- Sulfacetamide
Term
How do sulfa allergies work?
Definition
The allergy is to the sulfonamide + arylamine groups. Also a depletion in glutathione --> hapten formation
Term
How does Bactrim work?
Definition
Sulfamethoxazole/Trimethoprim are synergistic - very wide spectrum to include MRSA, P. aerug, and toxoplasma gondii
Term
What are the AEs of sulfonamides?
Definition
- Crystaluria - prevention by raising pH, drinking water, lowering pKa of compound
- Hypersensitivity
- Trimethoprim - Hyperkalemia
Term
What is the MoA of FQNs?
Definition
inhibition of DNA gyrase (topo 2) and topo 4 (opens replication fork, decatenation) - Inhibition of DNA replication
Term
What leads to resistance in FQNs?
Definition
- Gram(-) gyrase mutations lead to low or high
- gram(+) topo 4 mutations
Term
What agent is the only quinolone?
Definition
Nalidixic Acid/Negram - for gram(-), but P. aerug is resistant
Term
What agents are 2nd gen FQNs?
Definition
- Norfloxacin/Noroxin - Broad gram(-) spectrum including P. aerug
- Ciprofloxacin/Cipro - Broader spectrum, including better P. aerug, Legionella, Rickettsia, B. anthracis, Klebsiella, H. influenzae, cholera, and enterococci. **Crosses CSF
- Ofloxacin/Floxin - racemic
- Levofloxacin/Levaquin - better gram(+) coverage - MSSE, mycoplasma
Term
What are the major side effects of FQNs?
Definition
- Displacement of GABA leading to CNS excitation - due to piperazine
- Tendon rupture
- Proconvulsant
- Chelates cations
- QT prolongation
Term
What are properties of 2nd gen FQNs?
Definition
- Good for systemic infections
- Broad spectrum, especially against gram (-) including P. aerug
- Does NOT work against anaerobes
- Weak gram(+) activity
Term
What are 3rd generation FQNs?
Definition
S. pneumoniae coverage, better gram(+)
- Gatifloxacin/Zymar - only opth
Term
What are 4th generation FQNs?
Definition
- Moxifloxacin/Avelox - better against bacteria that live inside cells and anaerobes like bacteroides, S. pneumoniae. Loss of gram(-) activity
- Gemifloxacin/Factive - most gram(+) and gram (-) coverage, lowest resistance
Term
What is Hiprex used for?
Definition
Methenamine and Hippuric Acid/Hiprex - for UTI, a disinfectant that creates ammonia and formaldehyde.
**Proteus are resistant
Term
What are the differences in Furantin forms?
Definition
- Furadantin - Original, most N/V
- Macrodantin - macrocrystals
- Macrobid - mix of crystals and gel
**reduce flavoproteins, produce reactive intermediates to stop DNA and RNA. ONLY for E. coli and Enterococci
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