Antimicrobials Flashcards
T/F: All antimicrobials are antibiotics but not all antibiotics are antimicrobials
FALSE, all antibiotics are antimicrobials but not all antimicrobials are antibiotics
therapeutic use
when diseased animals are treated to cure infection
prophylactic use
when healthy herds or animals are treated to prevent infection
metaphylactic use
when diseased herds are treated to cure infection in some individuals and prevent infection in others
chemotherapeutic drugs
selectively toxic to the causative agent of disease (AMDs)
what are the two most important factors in determining what AMD to use?
efficacy and toxicity
intrinsic resistance
resistance due to structural or functional traits present in all members of a given bacterial species or group
mutant prevention concentration (MPC)
concentration of AMDs you give to avoid creating mutants
T/F: for time-dependent AMDs efficacy depends on amount of time that the drug concentration stays above the MIC
TRUE, aim to be above MIC for at least 50% of the dosing interval
T/F: if you give a higher concentration of a time-dependent AMD you can improve efficacy
FALSE, higher concentrations at the site of infection for time-dependent AMDs does NOT improve efficacy
danny tanner is tired of pilling comet 20 mg of amoxicillin TID, he asks if you can prescribe him a dose for BID. what do you tell him?
sorry danny! upping the dose so you can pill comet less is going to effect the efficacy of the drug! because amoxicillin is a time-dependent drug, it’s important to maintain your drug concentration
are penicillins and cephalosporins time-dependent or concentration-dependent?
time-dependent (T > MIC)
what is efficacy related to in concentration-dependent drugs?
the peak concentration being very high concentration at the site of infection, aim for Cmax that is 10x MIC!! (Cmax/MIC)
what kind of effect do you often see with concentration-dependent AMDs?
a long post-antibiotic effect (PAE)
you are working with a 100 year old vet who prescribes amikacin (aminoglycoside) to a patient with the directions to give small doses BID but you being a baby Dr. remember learning in class that this might not give you the best efficacy. how do you explain this to him?
when they first made amikacin they only looked at mg/kg how ever many times a day, its actually more efficacious when given at a larger dose once a day because it’s a concentration-dependent AMD, even though you’re technically going extra-label
name two major concentration-dependent AMDs
aminoglycosides and fluoroquinolones
what kind of group of AMDs are you describing when efficacy relates to both concentration and time, and is measured by looking at the AUC compared to MIC?
drugs that don’t fit into time-dependent or concentration-dependent nicely, AUC/MIC (overall drug exposure), tablet/capsule size, adverse effects, and owner compliance dictate dosing regimen
what AMDs would you look at AUC/MIC for measuring efficacy?
macrolides, lincosamides, tetracyclines, fluoroquinolones
how do you optimize dosage regimens?
shoot high, shoot low, shoot fast
drugs that distribute to the ECF
beta-lactams, aminoglycosides
drugs that distribute through the total body water
chloramphenicol, clindamycin, doxycycline, quinolones, sulfonamides
drugs that concentrate in the urine
beta-lactams, aminoglycosides, quinolones, sulfonamides
drugs that concentrate in the bile
clindamycin, doxycycline, erythromycin, rifampin
drugs that accumulate in WBCs
clindamycin, erythromycin, quinolones, rifampin
drugs that penetrate the BBB
chloramphenicol, doxycycline, quinolones, metronidazole, rifampin, potentiated sulfonamides
drugs that do not penetrate the BBB
aminoglycosides, some cephalosporins, clindamycin, erythromycin
what three AMDs accumulate in phagocytic cells?
macrolides, lincosamides, fluoroquinolones
what AMD is known to excrete unchanged in the bladder and therefore show high concentrations in the lumen of the bladder?
penicillins
T/F: inflammation can decrease drug delivery to the site of infection
FALSE, inflammation will result in increased blood flow, higher capillary permeability, etc. which will increase drug delivery to the site of infection
T/F: chronic inflammation may decrease efficacy of an AMD
TRUE, i.e. sulfas don’t work well in presence of pus which is high in PABA
in what type of patient would you want to use a bactericidal over a bacteriostatic drug?
immunocompromised
T/F: sulfonamides and fluoroquinolones are relatively safe as they have a much higher affinity for the bacterial target enzymes than mammalian enzymes
TRUE
what AMD can cause severe irritation to the esophagus and lead to esophageal stricture?
doxycycline
what AMD accumulates in renal cells and otic hair cells causing nephrotoxicity and ototoxicity?
aminoglycosides
what two AMDs more frequently stimulate immune mediated or allergic responses than other classes?
sulfonamides and penicillins
T/F: aminoglycosides have a wide TI, rarely significant adverse effects
FALSE, that is amoxicillin. aminoglycosides have a narrow TI, significant risk of renal toxicity
what AMD can cause retinopathy in cats?
enrofloxacin (fluoroquinolone)
what AMD can cause joint damage in young, growing animals?
enrofloxacin
what AMD has a higher incidence of hepatotoxicity in dobermans?
sulfonamides
what AMD can cause fatal GI microfloral disruptions in small herbivores?
penicillins (think guinea pig case based)
T/F: baytril (enrofloxacin) is approved in cattle but not dogs
FALSE, opposite
what are common AMDs that inhibit the cell wall?
beta-lactams (penicillins, cephalosporins)
what are common AMDs that disrupt the cell membrane?
polymyxins
what are common AMDs that inhibit protein synthesis?
macrolides and lincosamides, amphenicols, tetracyclines, aminoglycosides
what are common AMDs that inhibit DNA/RNA synthesis/function?
fluoroquinolones and sulfonamides
