Antimicrobial Review (extensive) Flashcards
lmk if there are any errors
What are the two main subdivisions of beta-lactam antibiotics
penicillins and cephalosporins
Name a benzylpenicillin
penicillin G
Name an aminopenicillin
ampicillin and amoxicillin
What is the spectrum of penicillin G
strep, anaerobes
What is the spectrum of aminopenicillins
gram neg aerobes in urine, strep, anaerobes
What is the spectrum of aminopenicillins with a beta-lactamase inhibitor
same as aminopenicillins (gram neg aerobes in urine, strep, anaerobes) plus methicillin susceptible staph and bacteroides
How is clavamox different from amoxicillin
it has a beta-lactamase inhibitor added (clavulonic acid)
How is unasyn different from ampicillin
it has a beta-lactamase inhibitor added (sulbactam)
Describe the pattern for the spectrum of cephalosporins
gram negative spectrum increases as generation number increases
gram positive spectrum may decrease as generation number increases (but 3rd just as good as 1st for gram +)
anaerobic spectrum variable
Name the first generation cephalosporins
cefazolin and cephalexin
(remember b/c a is 1st in the alphabet)
What is the spectrum of 1st generation cephalosporins
strep, methicillin susceptible staphs
cefazolin may get gram positive anaerobes and some gram negatives
Describe the use of 2nd generation cephalosporins
cefoxitin has very limited use in vetmed
may be used as surgical prophylaxis for severe dental/gingival dz (anaerobes)
What is the spectrum of 3rd generation cephalosporins
strep, methicillin susceptible staph (not ceftiofur), gram negative anaerobes (not ceftiofur), gram negatives at higher doses (cefpodoxime most active)
Name the third generation cephalosporins
ceftiofur, cefpodoxime proxetil, cefovecin
Summarize the spectrum of beta-lactam antibiotics
excellent for strep
cephalosporins better for staph (penicillins need BLI)
aminopenicillins (for UTI) and 3rd gen cephalosporins have best gram neg spectrum
penicillins and aminopenicillins have best anaerobic spectrum
What drugs are aminoglycosides
amikacin and gentamicin
What is the spectrum of aminoglycosides
gram neg, staph (use limited to MRS b/c of side effects), mainly used for severe gram neg aerobes
NO anaerobes and NO strep
In what environments do aminoglycosides become inactivated
purulent environments
What drugs are fluoroquinolones
enrofloxacin, marbofloxacin, orbifloxacin, pradofloxacin, ciprofloxacin
What is the risk with pradofloxacin use in dogs
bone marrow suppression, best to use a diff drug in the class
What is the risk with ciprofloxacin in horses
fatal colitis! do not use for horses!!
What is the spectrum of fluoroquinolones
gram neg, staph (save use for MRS), rarely gets strep, rickettsia, mycoplasma
NO anaerobes
very similar to aminoglycosides, but more active in purulent environments
What organ is at risk with aminoglycoside use
kidney toxicity
What tissue is at risk with fluoroquinolone use
cartilage
What drugs are tetracyclines
oxytetracycline, docycycline, minocycline
What is the spectrum of tetracyclines
gram positives, gram negatives, anaerobes, rickettsia
“jack of all trades…master of rickettsia”
lots of resistance out there. main use is for rickettsia
List the tetracyclines in order from most to least active
minocycline, doxycycline, oxytetracycline
What does it mean if a bacteria is susceptible to oxytetracycline
it is susceptible to all 3 tetracyclines
What does it mean if a bacteria is resistant to oxytetracycline
resistant to oxytet, but may be susceptible to the other 2 (minocycline and doxycycline)
What is the spectrum of potentiated sulfonamides
gram positives, gram negatives, and protozoa
“jack of all trades, master of none”
there is a lot of resistance so it doesn’t treat anything very well
What environments do potentiated sulfonamides not work well in
purulent
What do you need to keep in mind with susceptibility tests for sulfas
in vitro tests overestimate anaerobic activity, so don’t believe susceptibility tests on them
What drugs are macrolides
erythromycin, clarithromycin, azithromycin
What drugs are lincosamides
clindamycin
What species cannot have clindamycin and why?
horses and rabbits b/c lethal diarrhea
What is the spectrum of macrolides and lincosamides?
good for abscesses and intracellular bacteria
gram positive aerobes, anaerobes (clindamycin and sort of azithromycin, but macrolides rarely used for anaerobes)
What are macrolides commonly used for?
R.equi
azithromycin for small animal upper resp infections
What is the spectrum of phenicols
gram positive aerobes, anaerobes, some gram negatives, mycoplasma, rickettsia
good for abscesses and intracellular bacteria
Which drug classes are good for abscesses and intracellular bacteria
macrolides, lincosamides, phenicols
What drugs are nitroimidazoles
metronidazole
What is the spectrum of nitroimidazoles
anaerobes!!!
protozoa
do not work in the presence of oxygen
What is the MOA of beta-lactams
cell wall inhibitors
What is the MOA of fluoroquinolones
DNA gyrase inhibitors
What is the MOA of potentiated sulfonamides
folic acid inhibitors
What is the MOA of nitroimidazoles
DNA inhibitors via production of toxic metabolites
What is the MOA of aminoglycosides
protein synthesis inhibitors 30S
What is the MOA of tetracyclines
protein synthesis inhibitors 30S
What is the MOA of macrolides
protein synthesis inhibitors 50S
What is the MOA of lincosamides
protein synthesis inhibitors 50S
What is the MOA of phenicols
protein synthesis inhibitors 50S
Why do you have to be careful with procaine penicillin
it can cause seizures if any goes IV in horses
Which benzylpenicillin can go IV
potassium penicillin, but slowly b/c K can affect the heart
Which of the following penicillins are absorbed orally?
a. benzylpenicillins
b. clavamox
c. ampicillin
b and c in dogs and cats
(amoxicillin has better oral absorption than ampicillin)
Describe the distribution, metabolism, and elimination of penicillins
hydrophilic, minimal metabolism, renal elimination
Why are penicillins good for UTI
they are actively pumped into the urine, so there is a greater urine concentration than plasma concentration
What does it mean if a drug has extensive metabolism
liver disease causes the drug to stick around longer and risks toxicity
What does it mean if a drug is hydrophilic
it is confined to the plasma and extracellular fluid
What does it mean if a drug has active metabolites
liver disease means the liver doesn’t make the metabolite well and the drug doesn’t work
Which of the following cephalosporins are absorbed orally?
a. cefazolin
b. cephalexin
c. ceftiofur
d. cefovecin
e. cefpodoxime proxetil
b and e ( both in dogs and cats, but not horses)
cefpodoxime proxetil is absorbed orally in foals
Describe the distribution, metabolism, and elimination of cephalosporins
hydrophilic, minimal metabolism (except ceftiofur is highly), renal elimination
*Are beta-lactams time- or concentration-dependent? What does this mean for dosing?
time-dependent, so need concentrations greater than MIC for only a percentage of dosing interval
50% for immunocompetent patients with gram positive infections
redose more frequently with gram negatives or immunocompromised
Which of the following aminoglycosides can be absorbed orally?
a. amikacin
b. gentamicin
no oral absorption! sometimes used for “local” tx of GIT
Describe the distribution, metabolism, and elimination of aminoglycosides
hydrophilic, minimal metabolism, renal elimination
reabsorbed by kidneys, so if worried about an overdose, put on fluids to reduce the time the drug is able to be reabsorbed
*Are aminoglycosides concentration dependent or time dependent? What effect does this have on dosing?
concentration dependent
dose once per day to prevent nephrotoxicity associated with trough concentrations greater than 2 micrograms/mL
Which of the following drug classes are bactericidal and which are static?
a. aminoglycosides
b. beta-lactams
c. sulfonamides alone
d. potentiated sulfonamides
e. tetracyclines
f. fluoroquinolones
g. macrolides
h. lincosamides
i. nitroimidazoles
j. phenicols
cidal - a, b, d, f, i
static - c, e, g, h, j
What is the rule for MOA related to static vs cidal
all protein synthesis inhibitors (except for aminoglycosides) are static
all cell wall synthesis inhibitors and nucleic acid inhibitors are cidal
Which of the following fluoroquinolones are absorbed orally?
a. ciprofloxacin
b. enrofloxacin
c. pradofloxacin
a (dogs only), b, and c (decreased by food)
Describe the distribution, metabolism, and elimination of fluoroquinolones
lipophilic (esp enro) so suitable for CNS/prostate and gets intracellular, enro is metabolized to cipro, mostly renal elimination, enro has partial biliary elmination, *exception is prado has mostly hepatic elimination and only partially renal
How do renal/hepatic disease affect elimination of fluoroquinolones
with renal dz, liver elimination increases
with liver dz, renal elimination increases
therefore you do not need to alter the dose
*Are fluoroquinolones time or concentration dependent? What does this mean for dosing
concentration dependent, but dose based on AUC (which looks at concentration over time)
typically increase dose to improve efficacy but can decrease dose interval
*some people do 1/2 dose BID. don’t do that
Which of the following tetracyclines are absorbed orally?
a. doxycycline
b. minocycline
c. oxytetracycline
a and b (both good in dogs and cats, ok in horses)
Describe the distribution, metabolism, and elimination of tetracyclines
well distributed, intracellular, doxy is most lipophilic but highest protein binding so limited access to protected sites, minocycline best for protected sites, no active metabolites, minocycline mostly hepatic elimination, doxycycline renal and hepatic elimination, oxytet mostly renal elimination
Describe the distribution, metabolism, and elimination of potentiated sulfonamides
moderately lipophilic, highly metabolized by liver, mainly renal but some hepatic elimination
Are potentiated sulfonamides absorbed orally?
yes
Describe the distribution, metabolism, and elimination of macrolides
WIDE distribution, INTRACELLULAR, gets to protected sites but pumped out of cerebrospinal fluid, enter abscesses, extensive hepatic metabolism, mainly hepatic elimination
Are macrolides absorbed orally?
yes
Are lincosamides absorbed orally?
good for dogs and cats, but not horses (fatal diarrhea)
Describe the distribution, metabolism, and elimination of lincosamides
WIDE distribution, intracellular, not cerebrospinal fluid, extensive hepatic metabolism (so not for UTI)
Describe the distribution, metabolism, and elimination of chloramphenicol
WIDELY distributed, intracellular, readily enters protected sites, extensive hepatic metabolism, inhibits hepatic metabolism of other drugs, eliminated by metabolism but parent drug leftover excreted renally
Is chloramphenicol absorbed orally
moderate oral absorption
Describe the distribution, metabolism, and elimination of nitroimidazoles
WIDELY distributed, enters protected sites, extensive hepatic metabolism, mainly hepatic elimination (so not for UTI)
are nitroimidazoles absorbed orally
yes
which drugs classes DO NOT have oral absorption in dogs, cats, and horses
benzylpenicillins and aminoglycosides for all 3 species
horses - aminopenicillins, cephalosporins, macrolides (except foals), lincosamides
*which drug classes are hydrophilic and what does this mean clinically
penicillins, cephalosporins, aminoglycosides
cannot be used for protected sites
what adverse drug reactions are seen with penicillins
rare ADRs; hypersensitivity, neurologic at high doses, procaine reaction in horses, GI signs
what adverse drug reactions are seen with cephalosporins
rare ADRs; hypersensitivity, GI signs, reversible anemia and thrombocytopenia, bleeding disorders
what is the most important adverse drug reactions are seen with aminoglycosides? how can the risk be decreased
dose dependent nephrotoxicity.
risk greatly decreased with q24hr dosing, administration of calcium is protective, and fluid administration will decrease absorption
what are all the adverse drug reactions are seen with aminoglycosides
renal toxicity, ototoxicity (avoid topical use if eardrum ruptured), deafness in horses, vestibular toxicity, neuromuscular blockade with botulism
what adverse drug reactions are seen with fluoroquinolones
cartilage toxicity (puppies and foals most susceptible), ocular toxicity in cats (enro esp), pradofloxacin causes bone marrow suppression/maybe arrhythmias in dogs
what increases risk of cartilage toxicity with fluoroquinolones
more risk when younger, but at risk until bones are mature
more risk when heavier, more active, and more doses received
*how can risk of ocular toxicity with enrofloxacin be minimized in cats
stay below the maximum 5 mg/kg dose and keep the lights off
what adverse drug reactions are seen with tetracyclines
nephrotoxicity (oxytet only), idiosyncratic hepatotoxicity, esophageal ulcer/stricture in cats (doxy), rapid IV admin causes hypotension and collapse, skeletal effects, hypersensitivity and fevers in cats, photosensitization
what tetracycline cannot be given IV in horses
doxycycline IV in horses is fatal!
what species is most susceptible to ADRs from potentiated sulfonamides and why
dogs b/c they are deficient in acetylation and instead make a toxic metabolite
what adverse drug reactions are seen with potentiated sulfonamides
hypersensitivity esp in rotties and dobermans, idiosyncratic allergic/immune reactions in other breeds, hepatopathy and thrombocytopenia, rare dermatological emergencies, KCS w/ prolonged admin, “hypothyroid”, rare bone marrow suppression
what adverse drug reactions are seen with macrolides
GI in small animals, fatal diarrhea in adult horses, may decrease metabolism of some drugs (erythromycin), potentially fatal anhidrosis in foals (esp erythromycin)
what adverse drug reactions are seen with lincosamides
fatal diarrhea in horses and rabbits (DO NOT USE IN THEM), C. diff colitis, anorexia, vomiting, pain at inj site, esophageal ulcers in cats
what adverse drug reactions are seen with chloramphenicol
dose-dependent reversible anemia/neutropenia in cats with >60mg/kg/day, rare aplastic anemia/neutropenia in dogs, idiosyncratic aplastic anemia in people
what adverse drug reactions are seen with florfenicol
dry eye with long-acting otic preparations (not used systemically in dog, cat, or horse)
what adverse drug reactions are seen with nitroimidazoles
reversible neurotoxicity
which drug classes have a large volume of distribution
macrolides, phenicols, fluoroquinolones (esp enro), lincosamides (esp clinda), metronidazole
*macrolides and lincosamides not great for CNS b/c pumped out
