wk6:AED - Antibacterial 2 Flashcards
Name 5 antibiotics that can be given orally
penicillin cephalosporin macrolides fluorooquinolones tetracyclines
How commonly is penicillin used in eye care?
rarely
How does penicillin work?
inhibits bacterial cell wall synthesis
Is penicillin bacteriostatic or cidal?
bactericidal
Are most staphylococci sensitive or resistant to penicillin?
resistant (they produce an enzyme penicillinase that degrades the clinical efficiency of penicillins)
What is special about dicloxacillin (in relation to penicillins)?
penicillinase resistant
What is amoxycillin?
is a classic synthetic penicillin
How can we improve the spectrum of activity of amoxycillin?
Combine with potassium clavulanate (a beta lactase inhibitor)
How does the spectrum of activity of amoxycillin-clavulanate compare with amoxycillin?
Extended coverage of gram positives, some gram negatives
How good of a choice is amoxycillin-clavulanate for common eye and eyelid infections?
excellent choice
What is the standard dosage of diicloxacillin treatment? Why?
250mg qid. due to short half life.
Is dicloxacillin taken with meals?
Doesn’t have to be
What are the standard doses for amoxycillin-clavulanate treatment? (3)
Depends on severity.
Mild = 500mg
Most = 875mg
Severe = 1000mg
List 6 potential side effects of penicillins
Hypersensitivity reactions Up to 20% reported Most limited to skin rashes Severe anaphylaxis (uncommon) May also alter normal flora in resp. tract (super infections) Gastrointestinal upset
What 3 alternative antibiotics might you use if your patint is allergic to pnicillin?
Cephalosporin
Macroliides
Fluoroquinolone
Name a common first choice ophthalmic antibiotic
Cephalosporin
What part of bacteria is targeted with cephalosporin tx?
Bacterial cell wall synthesis (so similar to penicillins)
Do cephalosporins contain a beta lactam group?
yes, but derived from different amino acids than the penicillin beta lactam group
How long is a standard course of cephalexin (a type of cephalosporin, also known as keflex)?
1 week (lenght can change based on severi or condition)
What is the usual dosage of cephalexin?
500mg bid or 500mg qid
Why are cephalosporins contraindicated in hemophiliacs?
Because they can destroy intestinal bacteria which are necessary for the synthesis of vitamin K which can result in impaired blood clotting
What is the primary adverse reaction to cephalosporins?
hypersensitivity
What percentage of patients allergic to penicillin are also allergic to cephalosporin?
5-10%
this is known as cross sensitivity
Under what circumstances would cephalosporin be a suitable alternative for a penicillin allergy?
Only if minor adverse reaction to penicillin
What suitable alternatives can be used if a patient has a hx of penicillin anaphylaxis? (2)
Macrolides or Fluoroquinolones
Do fluoroquinolones have a broad or narrow spectrum?
broad
When are fluoroquinolones mainly used?
mainly reserved for when penicillin allergy
What is norfloxacin used for? (1)
tx of UTI
Provide an example fluouroquinolone, dose, and duration?
ciproflaxacin 500mg qd x 1 week
Are macrolides used as first line antibiotics?
usually NOT
Name 2 uses for macrolides
chlamydial infections
pregnancy
What part of bacteria do macrolides target?
inhibit protein synthesis
Are macroliides bacteriostatic or cidal?
mainly bacteriostatic but can be bactericidal in higher concentrations
What gram stain of bacteria are macrolides active against?
Gram +ve and some gram -ve
What properties do macrolides possess at low doses?
anti inflammatory properties
When might macrolides be used by clinicians?
As an alternative when tetracyclines are contraindicated
When is erythromycin (a macrolide) commonly used? (2)
Commonly used as a second choice antibiotic
Common choice in pregnancy
What is the ideal use for azithromycin?
excellent against chlamydial infections
What are the standard options when considering tx with macrolides? Outline procedure
Lab test azithromycin 1gm p.o single dose alternative or if unresponsive erythromycin 500mg qid, 7 days doxycycline 100mg bid 1 to 3 weeks
Out of the different tetracyclines, which one has the fewest potential side effects?
doxycycline
Describe how doxycycline affects cytokines?
reduces bioactivity of major inflammatory cytokines
In terms of the anti-inflammatory action of doxycycline, describe its effects (2) and describe at what dose (1)
at sub-optimal antibiotic doses
modify and enhance lipid metabolism
alter gland function, tear film function
How does doxcycline interact with MMPs?
inhibits theme
How do MMPs relate to eye problems? (1)
mmp is an enzyme implicated in corneal damage including recurrent erosion
Name 3 conditions where mmp is inhibited
mgd, dry eye, RCES
When would you prescribe doxycycline? (4)
topical medications ineffective
need repeat topical anti-inflammatory tx
severe inflammation ocular surface
significant lid disease
List 3 potential side effects of doxcycline
GI (drink full glass of water)
Yeast infections
Photosensitivity
How can we minimise the potential side effects of doxycycline?
use low dose
Describe 1 important interaction that doxycycline has that affects the medication
Ineffective when taken with dairy products or antacids
because calcium chelates the medication
do not take for at least 2 hours after dairy products
When is docycyline contraindicated? (3)
children under 8 years (may discolour teeth or hinder bone development)
pregnant or nursing women
renal function problems
What factors should you consider when deciding what antibiotic to prescribe to a patient? (8)
Age Weight General Health Mental status Allergy Hx Liver+Kidney function Current medications Pregnancy status
What are the 2 most important things to remember about doxycycline?
Function dependent on dose. One is antibiotic and other is MMP-9 inhibitor
