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Ocular Pharmacology > Antibiotic Classes: Sites of Action > Flashcards

Antibiotic Classes: Sites of Action Flashcards

1
Q

which antibiotics are cell wall inhibitors?

A

penicillins/cephalosporins, bacitracin, vancomycin

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2
Q

penicillins & cephalosporins are what kind of antibiotics? what is its MOA?

A

β-lactam antibiotics

β-lactam ring incorporates into cell wall → prevents bacteria from building it → eventually killing bacteria

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3
Q

what exists as part of the body’s own antibiotic system that break down cell wall bonds?

A

tear film lysozymes

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4
Q

which antibiotic is predominantly useful for treating G+ & anaerobic infections?

A

penicillins

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5
Q

PenG (IV, IM) & PenV (PO) belong to which class of penicillins?

A

PCNase sensitive

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6
Q

methicillin (IV, IM), cloxacillin, dicloxacillin are what class of penicillins?

A

PCNase resistant

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7
Q

ampicillin & amoxicillin are which class of penicillins?

A

aminopenicillins

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8
Q

carboxypenicillins: carbencillin & ticarcillin are what class of penicillins?

A

anti-pseudomonal (G-) coverage

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9
Q

Augmentin is composed of? how does it work?

A

amoxicillin + clavulanate → β-lactamase attacks clavulanate → amoxicillin left over & will be effective

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10
Q

why are there no topical formulations for penicillins?

A

allergy risk is too high

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11
Q

penicillins have a low but noticeable cross-sensitivity allergy risk with what antibiotic?

A

1st gen cephalosporins

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12
Q

what are the hypersensitivity type reactions to penicillin?

A
  • type I → anaphylaxis
  • type II → hemolytic anemia
  • type III → serum sickness
  • type IV → Stevens-Johnson syndrome
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13
Q

what is the structural difference between penicillins & cephalosporins?

A

cephalosporins have a β-lactam ring structure with 6 members

penicillins have a β-lactam ring structure with 5 members

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14
Q

unlike penicillins, cephalosporins are?

A

less susceptible to PCNase

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15
Q

which cephalosporin is used for most eyelid infections?

A

cephalexin (Keflex) 500mg BID PO x 7d

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16
Q

newer generations of penicillins & cephalosporins have greater G+ or G- coverage

A

greater G- coverage

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17
Q

is Bacitracin used for G+ or G- bacteria? where is its site of action

A

G+ → cell wall inhibitor

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18
Q

why is Bacitracin only available as a topical ointment?

A

it has profound nephrotoxicity

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19
Q

which Bacitracin ointment is well suited to staphylococcus blepharitis? Is it G+ or G-

A

AK-tracin ointment

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20
Q

which Bacitracin ointment provides additional G- coverage including pseudomonas? what does it additionally contain & what are their sites of action?

A

Polysporin ointment - Bacitracin + Polymyxin B

  • Bacitracin → cell wall inhibitor
  • polymyxin-B → cell membrane toxin
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21
Q

what antibiotic is the IV drug of choice for MRSA & MRSE infections & bacterial endophthalmitis? does it have G+ or G- coverage? where is its site of action?

A

vancomycin → G+ only → cell wall inhibitor

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22
Q

what are the adverse effects of vancomycin?

A
  • ototoxicity
  • nephrotoxicity
  • Red Man Syndrome
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23
Q

what is Red Man Syndrome?

A

IV-induced mast cell degranulation → histamine released → vasodilation → pt appears red

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24
Q

which antibiotics are cell membrane toxins?

A

polymyxin B & gramicidin

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25
Q

why are cell membrane toxins only available in topical form?

A

due to systemic toxicity

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26
Q

what is the mechanism of action of Polymyxin-B?

A

polymyxin incorporates into the cellular membrane → disrupts it → contents leak out

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27
Q

what is a cationic detergent/surfactant? does it work on G+ or G-?

A

polymyxin-B → G-

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28
Q

what antibiotic is only used topically, and never a stand-alone drug?

A

polymyxin-B

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29
Q

which cell membrane toxin has G+ coverage?

A

gramicidin

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30
Q

Polytrim solution, Polysporin ointment, Neosporin ointment & solution are all which antibiotic?

A

polymyxin-B combos

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31
Q

what are components in Polytrim solution? are their coverage G+ or G-? where is their site of action?

A

polymyxin-B + trimethroprim

  • polymyxin-B (cell membrane toxin) → G-
  • trimethoprim (folic acid inhibitors) → G+ & G-
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32
Q

what antibiotic combo is used for more common pediatric ocular infections? & from which organisms?

A

Polytrim solution

  • H. influenzae → polymyxin-B (G-)
  • S. pneumoniae → trimethoprim (G+ & G-, uses G- in this case)
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33
Q

why is Polytrim solution a good option for MRSA & MRSE?

A

because of the trimethoprim component (G+ & G- coverage)

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34
Q

what are the components in Polysporin ointment? what is the coverage & site of action?

A

polymyxin-B + Bacitracin

  • polymyxin-B → G- (cell membrane toxin)
  • Bacitracin → G+ (cell wall inhibitor)
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35
Q

what are the components in Polysporin ointment & what are their site of action & coverages?

A
  • polymyxin-B → G- (cell membrane toxin)

- Bacitracin → G+ (cell wall inhibitor)

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36
Q

what are the components in Neosporin ointment? what is their site of action & their coverages?

A
  • polymyxin-B → G- (cell membrane toxin)
  • neomycin → G- > G+ (protein synthesis inhibitor)
  • bacitracin → G+ (cell wall inhibitor)
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37
Q

what are the components in Neosporin solution? where are their sites of action & what is their coverage?

A
  • polymyxin-B → G- (cell membrane toxin)
  • neomycin → G- > G+ (protein synthesis inhibitor)
  • gramicidin → G+ (cell membrane toxin)
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38
Q

how do protein synthesis inhibitor antibiotics work?

A

bind to & inhibit 30S/50S ribosomal subunits of prokaryotes (bacteria)

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39
Q

which protein synthesis inhibitors inhibit 30S subunit? what is their coverage?

A
  • aminoglycosides (G- > G+)

- tetracyclines (G+ & G-) broad-spectrum

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40
Q

which protein synthesis inhibitor does not have any oral formulations?

A

aminoglycosides

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41
Q

neomycin, gentamicin & tobramycin are all what class of antibiotics? where is their site of action?

A

aminoglycosides → 30S protein synthesis inhibitors

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42
Q

which aminoglycoside is the oldest & is never used as a stand-alone? what is its coverage?

A

neomycin → G+ & G- (broad-spectrum, no pseudomonas)

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43
Q

which aminoglycoside is used for severe infections & why? what is its coverage?

A

gentamicin → G- > G+

- only used for severe infections bc too much toxicity

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44
Q

which aminoglycoside is the 2nd most effective against MRSA, following trimethroprim? what is its coverage?

A

tobramycin → (G- > G+)

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45
Q

which antibiotic is one of the few in pregnancy category B? where is its site of action?

A

tobramycin → 30S protein synthesis inhibitor

46
Q

why are aminoglycosides not typically administered orally? what do you do when you need to use it systemically?

A

they are poorly distributed from GI tract

when used systemically → given parenterally (injections)

47
Q

aminoglycosides can cause which type hypersensitivity reaction?

48
Q

SPK & delayed re-epithelialization, neurotoxicity, nephrotoxicity, & type IV hypersensitivity reaction are adverse effects of what class of antibiotics?

A

aminoglycosides

49
Q

corneal toxicity is most pronounced adverse effect of which aminoglycoside?

A

gentamicin

50
Q

routine use of neomycin can cause what adverse effect?

A

5-10% contact dermatitis risk

51
Q

tetracycline, doxycycline & minocycline are what class of antibiotics & what is their site of action & Gram covereage?

A

tetracyclines → 30S protein synthesis inhibitors

G+ & G-, broad spectrum

52
Q

what are tetracyclines used more for & how?

A

more used for their anti-inflammatory benefits

- inhibition of MMP’s neovascularization & bacterial lipases

53
Q

which tetracycline(s) are short-acting?

A

tetracycline

54
Q

which tetracycline(s) are long-acting?

A

doxycycline & minocycline

55
Q

what is minocycline indicated for? what class of antibiotics does it belong to & what is its site of action? what is its Gram coverage?

A
  • used for acne rosacea (from bacterial lipases/demodex)
  • tetracycline 30S protein synthesis inhibitor
  • G+ & G- (broad spectrum)
56
Q

what are the indications for doxycycline? what class of antibiotics does it belong to & where is its site of action? what Gram coverage does it have?

A
  • meibomian gland stasis, recurrent corneal erosions, acne roseacea
  • tetracycline 30S protein synthesis inhibitor
  • G+ & G- (broad-spectrum)
57
Q

doxycycline 50mg QD is used for what?

A

anti-inflammatory

58
Q

doxycycline 100mg QD is used for what?

A

kills bacteria

59
Q

what is the dosage of doxycycline for chlamydia +/- involvemenet (eg, trachoma)?

A

100mg BID x 7d

60
Q

what is the dosage of doxycyline for treating syphilis?

A

100mg BID x 14d

61
Q

which tetracycline can cause vestibular toxicity within 2-3d of therapy?

A

minocycline

62
Q

which tetracycline exhibits the least divalent chelation and has a risk of erosive esophagitis?

A

doxycycline

63
Q

which tetracycline is an excellent option for MRSE?

A

doxycycline

64
Q

what are the contraindications for use of tetracyclines?

A
  • pregnancy
  • nursing mothers
  • children under 8 yrs
  • renal failure
65
Q

which tetracycline can be used in patients with renal failure & why?

A

doxycycline → eliminated fecally

66
Q

erythromycin, clarithromycin & azithromycin belong to which class of antibiotics & where is their site of action? what is their Gram coverage?

A

macrolides → 50S protein synthesis inhibitor

G+ > G-

67
Q

which macrolide replaced silver nitrate prophylaxis for neonatal gonorrhea?

A

erythromycin

68
Q

which macrolide is unstable in gastric acid?

A

erythromycin

69
Q

which macrolide has reduced dosing because it has greater stability in the GI tract?

A

clarithromycin

70
Q

which macrolide is the only one available in drop formulation? what is that solution called?

A

azithromycin → Azasite solution w/ Durasite

71
Q

what permits azithromycin to have minimal dosing?

A

extended half-life

72
Q

which macrolide is contraindicated in pregnancy?

A

clarithromycin

73
Q

which macrolide can be used to treat bacterial conjunctivitis, bacterial infections, inclusion conjunctivitis & syphilis?

A

azithromycin

74
Q

what is the site of action for chloramphenicol & what is its Gram coverage?

A

50S protein synthesis inhibitors

G+ & G- (broad-spectrum)

75
Q

why is chloramphenicol limited to topical use only in the US?

A

high oral toxicity

76
Q

which protein synthesis inhibitor is a first-line therapy for bacterial conjunctivitis?

A

chloramphenicol

77
Q

what are the adverse effects of chloramphenicol when used orally?

A
  • blood dyscrasia risk
  • optic neuritis with prolonged therapy
  • gray baby syndrome
78
Q

what is the cell metabolism pathway?

A

PABA → dihydropteroate synthase → DHF acid → DHF reductase → tetrahydrofolic acid → nucleotides

79
Q

sulfonamides, trimethoprim & pyrimethamine are what class of antibiotics & where is its site of action? what Gram coverage do they have?

A

folic acid inhibitors → cell metabolism pathway

  • sulfonamides → G+ & G- (broad spectrum)
  • trimethoprim → G+ > G- (broad spectrum)
  • pyrimethamine → G+ & G- (broad spectrum)
80
Q

which folic acid inhibitor is a PABA analog & what is its MOA?

A

sulfonamides → mimics PABA & uses up dihydropteroate synthase → inhibits synthesis of dihydrofolic acid

81
Q

sulfonamides are commonly combined with which antibiotic? what is the ratio? why is it combined with this antibiotic?

A

commonly combined with trimethoprim in a 5:1 ratio

→ gives better effect because you disrupt two parts of the cell metabolism pathway

82
Q

which folic acid inhibitor is a DHF analog? what is its MOA?

A

trimethoprim → attacks DHF reductase → inhibiting synthesis of tetrahydrofolic acid

83
Q

pyrimethamine inhibits which part of the cell metabolism pathway?

A

inhibits DHF reductase

84
Q

which folic acid inhibitor is combined with another antibiotic & is the drug of choice for pediatric bacterial conjunctivitis? what are the sites of action & Gram coverage?

A

trimethoprim (folic acid inhibitor) + polymyxin-B (cell membrane toxin) → Polytrim solution

  • trimethoprim → broad spectrum (slightly more G+)
  • polymyxin-B → G-
85
Q

what folic acid inhibitor combination is used to treat toxoplasmosis?

A

sulfadiazine + pyrimethamine

86
Q

which folic acid inhibitor combination is the oral drug of choice for MRSA?

A

sulfamethoxazole + trimethroprim (Bactrim)

87
Q

which folic acid inhibitor is contraindicated in pregnancy?

A

sulfonamides

88
Q

cross-reactivity is common within with folic acid inhibitor group?

A

sulfonamides

89
Q

which folic acid inhibitor can cause bone marrow suppression?

A

trimethoprim

90
Q

which folic acid inhibitor can cause contact dermatitis or Stevens-Johnson syndrome

A

sulfonamides

91
Q

what class of antibiotics are fluoroquinolones & where is their site of action? what is their MOA? what is their Gram coverage?

A

DNA synthesis inhibitors → nucleid acid synthesis

  • inhibits DNA gyrase & topoisomerase IV
  • G- > G+
92
Q

ciprofloxacin & ofloxacin are which generation of fluoroquinolones?

93
Q

levofloxacin is which generation of fluoroquinolones?

94
Q

moxifloxacin & gatifloxacin are which generation of fluoroquinolones?

95
Q

besifloxacin w/ Durasite is which generation of fluoroquinolones?

A

“5th” gen

96
Q

which class of antibiotics are most commonly used & why?

A

fluoroquinolones because of their great coverage

97
Q

in fluoroquinolones, the newer the generation…

A

the greater the G+ coverage (along with G- coverage)

98
Q

using fluoroquinolones to treat what is FDA approved?

A

bacterial conjunctivitis

99
Q

using fluoroquinolones to treat what is off-label use?

A

bacterial keratitis

100
Q

which fluoroquinolone is 1st gen & can cause intracranial hypertension?

A

nalidixic acid (NegGram)

101
Q

which fluoroquinolone is the only topical antibiotic that lacks a preservative? what generation is it?

A

moxifloxacin → 4th gen

102
Q

which fluoroquinolone is concentration dependent? what does that mean? what generation is it?

A

gatifloxacin → 4th gen

the more the patient uses it → the better it does its job

103
Q

which fluoroquinolones are 100% effective when used for most common pediatric ocular infections?

A

levofloxacin, moxifloxacin, gatifloxacin

104
Q

which fluoroquinolone is only available as a topical suspension? what is it combined with & why? what generation is it?

A

besifloxacin → 5th gen

- uses Durasite as a viscous agent

105
Q

besifloxacin demonstrates promising MRSA sensitivity, but ineffective for what?

A

coagulase negative staph

106
Q

what G+ bacteria are antibiotic resistant?

A
  • enterococcus (VRE)

- staph aureus (MRSA)

107
Q

what G- bacteria are antibiotic resistant?

A
  • klebsiella
  • acinetobacter
  • pseudomonas
  • extended spectrum beta lactamase (ESBL): e. coli, enterobacter
108
Q

what are the 3 most common topical steroid/ABX combos?

A

blephamide, maxitrol, tobradex

109
Q

what are the contents in Blephamide? what is the Gram coverage and what class of antibiotic is in it?

A

sulfacetamide + prednisolone acetate

  • sulfacetamide → sulfonamides (folic acid inhibitor - inhibits dihydropteroate synthase)
  • sulfacetamide → broad-spectrum
110
Q

what are the contents in Maxitrol? what Gram coverage does it have? what antibiotic class is it & where is the site of action?

A
  • neomycin (aminoglycoside - 30S protein synthesis inhibitor) G- > G+
  • polymyxin-B (cell membrane toxin) G-
  • dexmethasone (steroid)
111
Q

what are the contents in TobraDex? what Gram coverage does it have? what class of antibiotics is in it? where is its site of action?

A
  • tobramycin (aminoglycoside - 30S protein synthesis inhibitor) G- > G+
  • dexamethasone (steroid)

Ocular Pharmacology (9 decks)

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