Antibiotics Flashcards
Resistant enterobacteriaceae
Esp E. coli and K. pneumoniae
- Extended spectrum beta-lactamase (ESBL) producers - Carbapenemase producing enterobacteriaceae (CPE)
- Kiebsiella producing carbapenemases (KPC)
Antimicrobial stewardship
- The long-term effects of antimicrobial selection, dosage, and duration of treatment on resistance development should be a part of every antimicrobial treatment decision
Amoxicillin
Amoxicillin is a penicillin. Specifically it is an aminopenicillin (good oral bioavailability, longer half-life than penicillin V, better activity against some Gram negative bacteria)
What is amoxicillin used to treat
It is used in the treatment of S. pyogenes infections (sore throat, skin infections), pneumococcal infections (respiratory tract) and coliform infections (urinary tract infection).
Amoxicillin mechanism of action
Inhibition of bacterial cell wall synthesis
Amoxicillin adverse effects
- Allergy
- Damage to commensal microflora
Amoxicillin standard dose
250-1000mg 8 hourly
Amoxicillin oral bioavailability
good
Amoxicillin half-life
1 hr
Amoxicillin excretion
urine
Amoxicillin interactions
Can increase levels of other protein bound drugs
Sore throat infection
Amoxicillin
Common side effect of penicillins in a patient with glandular fever
- Giving penicillins can cause a rash
Pseudomonas treatment
- Piperacillin anti-pseudomonas antibiotic
Penicillin allergy classification
Immediate/accelerated - type 1(0.02% of courses)
Delayed - mixed mechanisms (2-3% of courses)
Penicillin allergy - immediate/accelerated - type 1
- 0-72 hrs after exposure
- IgE mediated, mast-cell mediated
- Urticaria, wheeze, life threatening
Penicillin allergy - delayed mechanisms(2-3% of courses)
> 72 hrs after exposure
- Will worsen with repeated exposure
- Does not become immediate type
Cephalosporin allergy
Very complicated - lots of potential haptens involved
- Not a class effect
- Penicillin X-reactivity more with 1st and 2nd generations
Risk - 8% if previous penicillin allergy
- Less with 3rd generation
Clarythromycin
- Is a similar spectrum of action to amoxicillin and is used for patients with penicillin allergy
What is clarythromycin used to treat
Treatment of S.pyogenes infections(sore throat, skin infections), pneumococcal infections(resp tract) and coliform infections(urinary tract infection)
- Also active against cell-wall deficient bacteria(e.g. chlamydia) which cause penumonia and genitourinary infections
Clarythromycin mechanism of action
- Inhibition of protein synthesis in the bacterial ribosome (50S subunit)
Clarythromycin - oral bioavailability
good
Clarythromycin - metabolism
hepatic
Clarythromycin - excretion and halflife
Half-life - 1-6 hrs
Clarythromycin - standard dose
500mg
12 hrly
Clarythromycin - adverse effects
- Nausea and diarrhoea
- May alter cardiac conduction –> arrhythmias
Clarythromycin interactions
- Inhibits enzymes (cytochrome p450 enzymes) involved in the metabolism of other drugs
Vancomycin
- Is a glycopeptide
- Is active only against gram-positive bacteria and is active against many resistant strains including MRSA
Vancomycin mechanism of action
- Inhibits bacterial cell wall (peptidoglycans) formation by a different target to beta lactams
Vancomycin standard dose
500-1500mg 12 hourly
Narrow therapeutic window
Dose by drug levels in blood
Vancomycin oral bioavailability
Very low
Vancomycin metabolism
None
Vancomycin half-life
4-8 hrs
Vancomycin excretion
urine
Vancomycin adverse effects
Nephrotoxic
Ototoxic
Vancomycin interactions
Other ototoxic or nephrotoxic drugs
When is vancomycin administered orally
- C.diff
Doxycycline
- Tetracycline
What is doxycycline effective against
- Good activity against gram positives (streps and staphs) some gram negs (haemophilus)
- Also active against cell-wall deficient bacteria(e.g. chlamydia)
- Used for skin, resp tract, genital tract infections
Doxycycline mechanism of action
- Inhibition of protein synthesis in the bacterial ribosome(30S subunit)
Doxycycline standard dose
100-200mg daily
Doxycycline oral bioavailability
good
Doxycycline metabolism
None
What is doxycycline poor against
Poor against enterobacteriaceae, anaerobes
Doxycycline half-life
6-12 hrs
Doxycycline excretion
urine and bile
Doxycycline adverse effects
Dyspepsia
Photosensitivity
Avoid in pregnancy/children (teeth)
Doxycycline interactions
- Competes for protein binding
- Warfarin, digoxin etc
What is nitrofurantoin used for
Wide spectrum - esp E. coli and some other enterobacteriaceae, also enterococci, staphs, some streps
Nitrofurantoin mechanism of action
- Complex
- Damages bacterial DNA
- High resistance threshold?
Nitrofurantoin excretion
urine
Nitrofurantoin metabolism
none
Nitrofurantoin half-life
1 hr
Nitrofurantoin oral bioavailability
good
Nitrofurantoin standard dose
50mg qds
Nitrofurantoin adverse effects
V well tolerated
Safe in early pregnancy - avoid late
Avoid in renal impairment - peripheral neuropathy, doesn’t penetrate urine if eGFR low
Nitrofurantoin interactions
- No major issues
What is nitrofurantoin the first line antibiotic for
- UTIs
Nitrofurantoin interactions
- No major issues