Antibiotics Flashcards
What are some ways of antibiotics resistance?
- Prevent access to bug
- Bug produces destructive enzymes (penicillin)
- Bug changes drug binding sites
- Drug pumped out of bug (penicillin)
- Bug creates bypass pathways to overcome loss of function
General principles of prescribing antibiotics?
- Use only when there are demonstrated significant benefits
- Use the narrowest spectrum to cover the likely pathogens
- Single agents unless combination proved superior
What does beta lactams penicillin do?
Bactericidal: inhibit bacterial cell wall synthesis
What organisms do beta lactams penicillin act on?
predominantly G+
by adding different side chains to broaden activity to include G- and pseudomonas
Empirical vs targeted?
If organisms not known, start with empirical
When organisms and sensitivity are known, follow sensitivity provided rather than guidelines
Two types of beta-lactam antibiotics
penicillin
cephalosporins (broader-spectrum)
Penicillin allergy vs intolerance
Allergy: immunological reactions
skin reactions
Intolerance: diarrhoea, headache, vomiting
What is severe penicillin allergies?
Severe skin reactions +/- fever
Steven-Jones Syndrome
TEN Syndrome
DRESS Syndrome
- re-exposure leads to recurrent reaction and high mortality
- Give cephalosporins when clearly indicated the three syndromes
What is immediate hypersensitivity penicillin allergies?
IgE mediated: urticaria (itchy raised bumps), angioedema, anaphylaxis, dyspnoea, hypotension, deaths
- re-exposure leads to similar to worse reactions
- cephalosporins contraindicated
What is penicillin allergies without immediate hypersensitivity?
rash without other features described in immediate hypersensitivity
- re-exposure result in rash
Penicillin allergy/intolerance history?
What specific medication/range of antibiotics
What type of reaction: intolerance/allergy
Onset (few hours –> immediate hypersensitivity)
How was it treated?
What are some examples of Penicillin?
- Narrow spectrum (G+ cocci): benzyl penicillin, phenoxymethyl penicillin
- Narrow spectrum with anti-staphylococcal action: flucloxacillin
- moderate spectrum: amoxycillin
against G-, used for resp infections, often combine with others - broad spectrum
When are cephalosporins are used?
broader than penicillin
SECOND LINE due to increasing resistance of MRSA, VRE and C. difficile
DONT: penicillin immediate hypersensitivity (cross-reactivity)
When are some examples of cephalosporins?
third generation: ceftriaxone commonly seen
What are some examples of other antibiotics?
aminoglycosides (gentamicin) macrolides (erythromycin, azithromycin) quinolone (moxifloxacin) Vancomycin tetracycline (doxycycline)
When is aminoglycosides used?
Gentamicin G- infections 100% renally eliminated Side effects - nephrotoxocity - ototoxicity
When is macrolides used?
azithromycin, erythromycin inhibit protein synthesis Indications - Mainly G+ - some G- (strep, H pylori, H influenzae) - PENICILLIN ALLERGY
When is quinolone used?
moxifloxacin broad spectrum (G+ & -) indication - use when renal impairment - immediate hypersensitivity to penicillin
When is Vancomycin used?
Use is severely restricted to reduce Vancomycin resistant staph aureus
Effective towards MRSA
G+ resistant to penicillin
When is tetracycline used?
tetracycline doxycycline broad: chlamydia, malaria side effect - discolours teeth permanently
What does Metronidazole do?
inhibit DNA synthesis of anaerobes
When patient is allergic to penicillin, what antibiotic should be given?
From the antibiotics that the organism is sensitive to
- no beta lactams
penicillin: allergic
cephalosporins: might lead to cross reactivity with immediate hypersensitity
- vancomycin
can give but need to reserve for MRSA
- Macrolides - thromycin
(G+, G- strep, H influenzae, penicillin allergies)
- Quinolone - moxifloxacin
broad spectrum, used when others cant such as renal or allergy
