Fluoroquinolones Flashcards
What is the mechanism of action of FQs?
Inhibit DNA gyrase and topoisomerase
Are FQ bacteriostatic or bactericidal?
Bactericidal (due to inhibition of 2 enzymes)
What is the spectrum of the FQs?
Gram (+) and gram (-), but NO ANAEROBES
Nalidixic acid is the non-fluorinated precursor that only kills some gram (-). What is added to extend the spectrum of FQs to gram (+)s?
Fluorine
What is the most common method of resistance to FQs?
Point mutation in DNA gyrase genes
Which bug has the fastest development of resistance against the FQs?
Campylobacter
Are FQs time, concentration, or AUC/MIC-dependent?
AUC/MIC-dependent
What is the MPC?
Mutation prevention concentration
What is the MPC for gram (+)?
x5
What is the MPC for gram (-)?
x10
In what 3 tissues do the FQs concentrate?
- WBCs
- Prostate
- Brain
Are FQs water soluble or lipid soluble?
Lipid soluble (high Vd)
True or False: FQs are not absorbed well orally.
FALSE
True or False: FQs are excreted mostly unchanged in the urine.
TRUE
What toxicities are associated with the use of FQs?
- Chondrotoxicity in neonates/juveniles
- Retinopathies in cats
- Exacerbates seizures in epileptic dogs
- Herxhimer’s reaction
- Inhibit p450 enzymes
In which animals is the use of FQs banned?
- Poultry
2. Food animals
Which FQ is non-retinotoxic and used in the cat?
Pradofloxacin
What is the MOA of novobiocin?
Prevents ATP from binding DNA gyrase
Is novobiocin bacteriostatic or bactericidal?
Bacteriostatic
Which bacterium is included in the limited spectrum of novobiocin?
Staph aureus
What is the MOA of rifampin?
Inhibits RNA polymerase
What is the spectrum of rifampin?
- Mycobacteria
2. Gram (+)
With which of the following does resistance develop rapidly, rifampin or novobiocin?
Rifampin
What are the 2 side effects of IV rifampin in horses?
- Sweating
2. Hemolysis
What are the 3 toxicity issues associated with rifampin?
- Orange discoloration of bodily fluids
- Immune-mediated hepatitis
- Inducer of microsomal enzymes
What is the MOA of glycopeptides?
Cell wall synthesis inhibition
Are glycopeptides bacteriostatic or bactericidal?
Bactericidal
What is the spectrum of glycopeptides?
Gram (+)
Name 3 glycopeptide drugs.
- Vancomycin
- Teicoplanin
- Avoparcin
Only use glycopeptides if absolutely necessary. What are 4 things to take into consideration when using this drug?
- Vomiting likely
- Nephrotoxic
- Ionized in the gut (must be injected)
- Tissue irritant (slow IV drip)
Rifampin can be used against Rhodococcus equi in the horse. Combine this drug with what?
Clarithromycin
