AED - Anti-bacterial Agents II - Week 6 Flashcards
What 8 factors are taken into account when prescribing an antibiotic?
Age
Weight
General health status
Mental status
Allergy history
Liver and kidney function
Present medications
Pregnancy status
List the 5 classes of commonly used antibiotics.
Penicillins
Cephalosporins
Macrolides
Fluoroquinolones
Tetracyclines
Are penicillins commonly used in eyecare?
No, rarely used
Are penicillins bacteriostatic or bactericidal?
Bactericidal
Which bacterial species produce penicillinase?
Most staphylococcal species
Can penicillins be penicillinase resistant?
Yes
What is the dosage for dicloxacillin and why? Must it be taken with meals?
It has a short half life, so therefore 250mg q.i.d
Can be taken without regard to meals
What is a classic synthetic penecillin? Give its alternate name as well and describe why it is named so (name the component as well).
Amoxycillin
It is combined with a beta lactam inhibitor, potassium clavulanate
This increases its spectrum
It is also known as augmentin
What is the dosage of amoxycillin based on? Give the dosage (4).
Based on severity of the condition
Mild - 500mg
Most - 750mg
Severe - 1000mg
Taken b.i.d for 1 week
What are most penicillin side effects limited to?
Skin rashes
Up to what percentage are penicillin hypersensitivity reactions reported?
20%
Is severe anaphylaxis common with penicillins?
Uncommon
Does penicillin alter the normal flora of t respiratory tract?
Yes
What are three options if the patient is allergic to penicillins?
Cephalosporins
Macrolides
Fluoroquinolones
What is the first choice ophthalmic antibiotic?
Cephalosporins
How are cephalosporins related to penicillins?
Has a beta lactam ring, but with different amino acids
Give an example of a cephalosporin and the usual dose.
Cephalexin
500mg q.i.d for 1 week
What is a consequence of taking cephalosporins and in patients with which disease is it contraindicated?
It can kill intestinal bacteria necessary for synthesising vitamin K, which can impair clotting
Contraindicated in haemophiliacs
What is the primary adverse reaction to cephalosporins?
Hypersensitivity
What percentage of individuals allergic to penicillin are also allergic to cephalosporins, if any?
5-10%
If there is a minor adverse reaction to penicillin, is selection of cephalosporins still common? What about if there is a history of anaphylaxis to penicillins (2)?
Minor - selection is common
If there is a history of anaphylaxis, then consider a macrolide or a fluoroquinolone
Is fluoroquinolone narrow or broad spectrum?
Broad spectrum
What is fluoroquinolone reserved for?
When there is penicillin allergy
Give an example of a fluoroquinolone and the dosage.
Ciprofloxacin
500mg q.i.d for a week
Are macrolides typically a first-line antibiotic?
No
List two cases where macrolides are generally used.
Chlamydial infections
Pregnancy
How do macrolides work? Are they bacteriostatic or bactericidal?
Inhibit protein synthesis
Mainly bacteriostatic but can be bactericidal in higher concentrations
What properties do macrolides have at low doses?
Anti-inflammatory
What is the alternative when tetracyclines are contraindicated?
Macrolides
What antibiotic (name specifically) is commonly used as a second choice and in what population is it a common choice in?
Erythromycin
Common choice in pregnancy
What is azithromycin good against?
Chlamydial infections
What is the dose for azithromycin for chlamyia? What about erythromycin and doxycycline?
Azthromycin - 1gm p.o single dose
Erythromycin - 500mg q.i.d for a week
Doxycycline - 1000mg b.i.d for 1 to 3 weeks
Are the use of tetracyclines common or limited? Explain why.
Limited due to resistance
What tetracycline is the most effective in ocular disease? Explain why.
Doxycycline, it has the fewest potential side effects
What does doxycycline decrease the bioactivity of?
Major inflammatory cytokines
How does doxycycline affect lipid metabolism?
Modifies and enhances it
How does doxycycline affect the eyelid glands (2)?
Alters gland and tear film function
How does doxycycline treat surface ocular disease (2)?
Inhibits the formation of cytokines
Damages the enzyme MMP
What is MMP implicated in?
Corneal damage (such as recurrent erosion)
In what 4 cases are tetracyclines prescribed?
When topical medication is ineffective
Needs repeat topical anti-inflammatory treatment
Severe inflammation of the ocular surface
Significant lid disease
List 3 potential side effects of doxycycline. What is it minimised by?
GI disturbance (drink with water)
Yeast infections
Photosensitivity
Minimised by a low dose
Doxycycline is ineffective when taken by what two other products? Explain why and how long one should wait between taking the two.
Ineffective when taken with dairy products or antacids
Calcium chelates the medication
Wait 2 hours between the two
In what four cases is doxycycline contraindicated?
Children <8 years
Osteoporosis
Pregnant or nursing women
Poor renal function
What may doxycycline do to bone and teeth?
May discolour teeth and hinder bone development
