2: Clindamycin + Tetracyclines + Chloramphenicol Flashcards Preview

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Flashcards in 2: Clindamycin + Tetracyclines + Chloramphenicol Deck (44)
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31

oxytetracycline: original organism

strep rimosis

32

doxycycline: contraindications

decrease oral absorption 20% if taken with food or milk

33

doxycycline: bioavailability

90-100%, orally

34

doxycycline: why no toxic intermediate?

no -OH on C6

35

doxycycline: why is it the preferred tetracycline?

-good bioavailability
-lesser degree of absorption reduction w/ food/milk
-less GI sx
-no toxic intermediate
-t1/2 = 18-22h (once a day dosing)

36

where does chloramphenicol come from?

strep venezuelae

37

chloramphenicol MOA

-binds reversibly to 50@ at a site near the site for erythro/clinda (competitive binding interactions among these drugs)
-inhibits peptidyl transferase -> blocks peptide bond formation b/w P and A sites

38

chloramphenicol uses

-ointment/eye drops: bacterial conjunctivitis
-chloramphenicol Na succinate = prodrug for IV/IM admin:
-hydrolyzed to chloramphenicol in liver
-bacterial meningitis
-typhoid fever
-Rickettsial infections
-intraocular infections

39

why is it important that chloramphenicol is lipid soluble?

remains relatively unbound to plasma proteins -> penetrates into all tissues, including brain

40

chloramphenicol resistance: 3 mechanisms

1. decrease membrane permeability
2. mutation of 50S subunit
3. elaboration of chloramphenicol acetyltransferase (don't bind 50S)

41

chloramphenicol toxicity, worst one

aplastic anemia:
-rare, but generally fatal
-weeks to months post treatment
-highest risk w/ oral suspension
-lowest risk w/ eye drops
-keep blood levels

42

chloramphenicol toxicity, common ones

-bone marrow suppression due to impairment of mitochondrial fxn once you reach a cumulative dose of 20g (completely reversible)
-increased risk of childhood leukemia + risk increases with length of treatment
-adults: nausea, vomit, diarrhea (rare in kids)

43

chloramphenicol metabolism

turned into its glururonide in liver (inactive) -> excreted by kidneys
-therefore must decrease dose if decreased hepatic fxn

44

why should you never give neonates chloramphenicol?

they can't metabolize it