5 - Antibiotics

Question 1

List 3 beta-lactam antibiotics.
- How do they work?

Answer 1

• Penicillin
• Cephalosporins
• Carbapenems
  Bind to enzymes that usually cross-link cell wall.

Question 2

For penicllins, cephalosporins, and vancomycin, list
1) The main organism sensitive to it
2) Resistance levels
3) side effects

Answer 2

1) All gram +ve
2) Common, low in +ve, low in +ve
3) Allergy + GI upset, low, low

Question 3

Polymyxin B
- Mechanism?
- Best against?
- Use in optom?

Answer 3

• Disrupts osmotic integrity of cytoplasmic membrane
• Best against gram –ve
• Often combo w/ steroid called maxitrol

Question 4

Aminogylcosides
- Mechanism?
- Name the different drugs
- Best against?
- Side effects
- How often to take?

Answer 4

• Inhibits protein synthesis
• Gentamycin, neomycin, tobramycin, framyecetin
• Best against gram –ve
• Serious allergies common
• Qid to q1h

Question 5

Tetracycline
- Mechanism?
- Best against?
- Main ophthalmic use?
- How often take?
- Side effects?
- Contraindications?

Answer 5

• Inhibit protein synthesis
• Best against gram +ve
• Superifical infection
• Qid
• Stain teeth, photophobia
• Pregnancy, lactation, under 12yr old

Question 6

Doxycycline
- Mechanism?
- Best against?
- Use case?
- Dose/concentration?
- Side effects?
- Contraindication?

Answer 6

• Inhibit protein synthesis
• gram +ve (some gram –ve)
• Lid + superificial infections
• 50mg or 100mg
• Staining teeth, photophobia
• Osophageal ulceration. In general, avoid in kids.
• Take w/ large drink of water/milk
• Avoid sunburn
• Avoid at bedtime

Question 7

Azithromycin
- Mechanism
- Best against?
- Use case?
- Dose
- Side effects?

Answer 7

• Macrolide inhibits protein synthesis
• Gram +ve (some gram –ve)
• Lids
• 250mg or 500mg
• GI problems, otherwise not common
  Note: In general, since drops can’t reach lids properly, oral route is best for lids.

Question 8

Chloramphenicol
- Mechanism
- Concentration/dose?
- Best against?
- Use case?
- Dose
- Side effects?

Answer 8

• Inhibit protein synthesis
• 0.5% drops/1% ointment
• Gram +ve AND –ve
• Conjunctivitis, blepharitis
• qid
• None when applied as drop/ointment

Question 9

Fusidic acid
- Mechanism
- Dose/concentration?
- Best against?
- Use case?
- Dose?
- Side effects?

Answer 9

• Inhibit protein synthesis
• 1% gel
• Gram +ve
• Conjunctivitis, belpharitis
• qid
• temporary sting (otherwise well tolerated)

Question 10

Ciprofloxacin
- Mechanism?
- Concentration/dose?
- Best against?
- Use case?
- Dose?
- Side effects?

Answer 10

• Fluoroquinlone inhibits DNA replication
• 0.3% drops
• Gram +ve AND –ve
• Microbial keratitis
• Variable
• Low. White precipitates can form after lots of fluoroquinolones. Due to fluoroquinolone going from acidic to alkaline environment where bacteria is. Ciprofloxacin comes out of solution when at ulcer. Seen as white crystals.
  No need to do anything about as white precipitates is a sign that ciprofloxacin is present at the eye as wanted.
• Note: Strongest eyedrop we have so we only use if sight-threatening