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PT 1 > L28 The Fluoroquinolones > Flashcards

L28 The Fluoroquinolones Flashcards

1
Q

Why were the Fluoroquinolones (FQ) developed and what is good about them?

A

In response to growing resistance; broad spectrum, improved PK - excellent oral bioavailability, tissue penetration, long half-lives (but resistance has begun to develop)

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2
Q

What is the MOA of FQs?

A

Inhibition of DNA synthesis via inhibition of bacterial topoisomerases (DNA gyrase - gram-negative target, topoisomerase IV - gram-positive target)

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3
Q

FQs are ___-dependent and ___ (cidal/static).

A

Concentration; bactericidal

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4
Q

What is the major mechanism of resistance to FQs and three other minor mechanisms?

A

Major: altered target sites (mutations in genes that code for topoisomerases) leading to decreased binding affinity

Minor: active efflux, decreased porin expression, plasmid-mediated resistance

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5
Q

___-resistance occurs between FQs.

A

Cross

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6
Q

What are the important available FQs?

A
  1. Ciprofloxacin (both)
  2. Levofloxacin (both)
  3. Moxifloxacin (both)
  4. Gemifloxacin (oral)
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7
Q

Discuss the spectrum of activity of FQs broadly.

A
  1. Gram positive aerobes
  2. Gram negative aerobes
  3. Some anaerobes
  4. Atypical bacteria
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8
Q

What is the most important Gram positive bacteria FQs have activity against? Which of the FQs are best for this activity?

A
  1. Streptococcus pneumoniae (including PRSP)

Also: MSSA, strep viridans, Enterococcus

Levo and moxi

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9
Q

What is the most important Gram negative bacteria FQs have activity against? Which of the FQs are best for this activity?

A
  1. Pseudomonas aeruginosa (though significant resistance has emerged) - NOT MOXI, Cipro > Levo

Also: enterobacteriaceae, H. influenzae, M. catarrhalis, Neisseria spp.

Levo and cipro

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10
Q

Moxifloxacin (only) has some activity against which anaerobes?

A

Bacteroides species

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11
Q

Which atypical bacteria do (all) FQs have excellent activity against?

A
  1. Legionella pneumophila
  2. Chlamydophila and Chlamydia spp.
  3. Mycoplasma spp.
  4. Ureaplasma urealyticum
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12
Q

Discuss the absorption, distribution, and elimination of FQs.

A
  1. Good bioavailability after oral administration
  2. Distribution is extensive - lung, skin/soft tissue, bone, urinary tract and prostate (only cipro/levo), CSF (only moxi)
  3. Renal (levo, cipro), Hepatic (moxi)
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13
Q

What are the clinical uses for FQs?

A
  1. Upper respiratory tract infections (all)
  2. Community-acquired pneumonia (NOT cipro)
  3. Nosocomial pneumonia (cipro and levo)
  4. CF exacerbations (cipro)
  5. UTI, pyelonephritis, prostatitis (cipro, levo)
  6. Bone, intra-abdominal (w/metronidazole), STDs, TB (levo, moxi)
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14
Q

What are the most important adverse effects of FQs?

A
  1. Cardiac: prolongation of QTC interval -> Torsades
  2. Articular cartilage damage (contraindication in children, pregnant/breastfeeding women)

Also: GI (C. diff. colitis), CNS, hepatotoxicity, phototoxicity, tendonitis, hypersensitivity, rash

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15
Q

What are the important drug interactions of FQs?

A
  1. All oral FQs interact with divalent and trivalent cations, which impair absorption and lead to clinical failure
  2. Warfarin (all)
  3. Theophyllin and Cyclosporine (cipro)
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16
Q

What is metronidazole most active against?

A

Anaerobe and protozoa

17
Q

What is the mechanism of metronidazole broadly?

A

Inhibition of DNA synthesis

18
Q

How does metronidazole inhibit DNA synthesis?

A

Anaerobes and microaerophilic bacteria have ferredoxins; these are proteins that donate electrons to form a highly reactive anion that damages bacterial DNA and inhibits synthesis. Ferredoxins activate metronidazole, a pro-drug, into this anion.

19
Q

Metronidazole is ___-dependent and ___ (cidal/static).

A

Concentration; bactericidal

20
Q

What are the mechanisms of resistance of Metronidazole?

A
  1. Altered growth requirements (better growth in higher oxygen decreases activation of met)
  2. Altered ferredoxin levels (less activation of met)
21
Q

Which anaerobic bacteria are most important acted upon by Metronidazole?

A
  1. Bacteroides spp.
  2. Clostridium spp.

Also: peptostreptococcus, fusobacterium, prevotella, H. pylori

22
Q

Discuss the absorption, distribution, and elimination of Metronidazole.

A
  1. Oral/IV, rapid/complete absorption
  2. Well-absorbed, penetrates CSF
  3. Eliminated by the liver
23
Q

What are the clinical uses of Metronidazole?

A
  1. Anaerobic infections (intra-abdominal, pelvic, SSTI, diabetic foot, decubitus ulcer, brain abscess)
  2. Pseudomembranous colitis due to C. diff.
  3. Trichomonas
24
Q

Discuss the adverse effects of Metronidazole, including the most common and most serious.

A

Most common: GI (nausea, vomiting, stomatitis, metallic taste)

Most serious: CNS (peripheral neuropathy)

Also: mutagenic, avoid during pregnancy/breastfeeding

25
Q

What are the important drug interactions with metronidazole?

A
  1. Warfarin (increase anti-coagulant effect)

2. Alcohol (disulfiram reaction)

PT 1 (34 decks)

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