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anti-microbials > Fluoroquinolones, Folic Acid Antagonists & Urinary Antiseptics > Flashcards

Fluoroquinolones, Folic Acid Antagonists & Urinary Antiseptics Flashcards

1
Q

Examples of fluoroquinolones

A

2G - Ciprofloxacin (oral, IV), Ofloxacin (oral)

3G - Levofloxacin (oral, IV)

4G - Gatifloxacin (topical - eyedrops)

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2
Q

Mechanism of action of fluoroquinolones

A

Inhibits DNA synthesis

  1. Blocks DNA gyrase - blocks relaxation of supercoiled DNA - blocks DNA replication
  2. Blocks topoisomerase - blocks separation of chromosomal DNA
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3
Q

PK of fluoroquinolones

A
  • absorption is affected by Ca and other divalent cations
  • well distributed, ofloxacin can penetrate CSF
  • accumulate in macrophages & polymorphs in high conc & carried to site of infection
  • cipro partially metabolized by CYP450 (liver)
  • renally excreted, accumulation occurs in renal impairment
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4
Q

Spectrum of activity & uses of fluoroquinolones (5)

A

Broad spectrum - gram neg, gram pos, mycobacterium tb

Ciprofloxacin

  1. Traveller’s diarrhea/food poisoning (enterobac)
  2. Prostatitis (E coli)
  3. UTI

Levofloxacin

  1. CAP (S pneum unresponsive to macrolides/doxy)
  2. Pulm TB 2nd line
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5
Q

Toxicity of fluoroquinolones (5)

A
  1. GIT related
  2. CNS related
  3. Tendinitis in adults - rare - most commonly Achilles tendon, may lead to tendon rupture esp in older patients
  4. CDAD
  5. ECG - QT prolongation
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6
Q

Contraindications of fluoroquinolones (4)

A
  1. Pregnancy/breastfeeding
  2. Children/elderly
  3. Anti-arrhythmic drugs
  4. Epileptic
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7
Q

Drug interactions of fluoroquinolones (5)

A
  1. Ciprofloxacin + theophylline - decreases theophylline clearance - toxicity - tremors, nervousness, cardiac dysrhythmias, seizures
    • NSAIDs - seizures
  3. Ciprofloxacin + anti-thrombotic (warfarin) - increased PT & risk of bleeding
  4. Ofloxacin/ciprofloxacin + Antacids - reduces bioavailability of fluoroquinolones
  5. Ciprofloxacin _ CYP450 inhibitors - increased levels of cipro
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8
Q

Examples of folic acid antagonists

A
  1. Sulphonamides - Sulphamethoxazole (SMZ) - oral
  2. Benzylpyrimidines - Trimethoprim (TMP) - oral, syrup
  3. Compound drugs - SMZ + TMP - Co-trimoxazole, trade names bactrim, septra - oral, IV, syrup
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9
Q

Mechanism of action of folic acid antagonists

A
  1. Competitive inhibition
    - SMZ inhibits dihydropteroate synthetase
    - TMP inhibits dihydrofolate reductase
  2. Produces sequential block of folic acid synthesis req for DNA synthesis

Bactericidal

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10
Q

Mechanism of resistance of folic acid antagonists (3)

A
  1. Increased number of competing enzymes
  2. Decreased affinity for drugs
  3. Decreased permeability to drugs
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11
Q

PK of folic acid antagonists

A
  • good oral bioavailability
  • widely distributed, enters CSF, crosses placenta
  • SMZ acetylated in the liver, TMP partially demethylated in liver
  • excreted renally mainly by glomerular filtration
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12
Q

Spectrum of activity & uses of folic acid antagonists (3)

A

Aerobic gram pos & gram neg

  1. UTI
  2. Traveller’s Diarrhea
  3. Pneumonia
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13
Q

Toxicity of folic acid antagonists (4)

A
  1. Rash
  2. GIT related
  3. Glossitis, stomatitis
  4. Hematologic - pancytopenia with megaloblastic anemia
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14
Q

Contraindications of folic acid antagonists (3)

A
  1. Newborns/breastfeeding mothers - SMZ can displace bilirubin from albumin binding sites - cross immature BBB - damage brain & nerves
  2. Enhances antithrombotic effect of warfarin, increases methotrexate levels
  3. Increases half life of phenytoin by inhibiting its metab
  • Give patients folinic acid (readily converted to tetrahydrofolic acid) to avoid folic acid deficiency
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15
Q

Mechanism of action of nitrofurantoin

A

Oral urinary antiseptic, eliminated renally, produces harmless brown discolouration in urine

  1. Microbes produce enzyme nitrofuran reductase - reduces drug to form highly reactive electrophilic intermediates
  2. Damages bacterial ribosomal proteins - inhibits protein synthesis
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16
Q

Spectrum of activity & uses of nitrofurantoin (2)

A

Staph, strep agalactiae, E coli, enterococcus

R - enterobacter, klebsiella, proteus, PAE

  1. Acute UTI
  2. Prophylaxis of lower UTI
17
Q

Toxicity of nitrofurantoin & contraindications (5+4)

A
  1. GIT disturbances
  2. Hypersensitivity - rash, pneumonitis
  3. Pulmonary interstitial fibrosis - chronic use
  4. Blood dyscrasias - neutropenia, hemolysis
  5. Hepatotoxicity
  6. Pregnancy
  7. Elderly
  8. Impaired renal function
  9. Underlying lung disease

anti-microbials (6 decks)

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