Antibiotics Flashcards
Main antibiotics to know about
Penicillins
Cephalosporins
Glycopeptides
Aminoglycosides
Macrolides
Quinolones
Metronidazole
Principles of rational antibiotic prescribing
The aetiological agent
- potential for AMR
The patient
The drug
- mechanism of action
- mechanism of resistance
- ket pharmacology
Monitoring
Antimicrobial stewardship
Key feature of healthy policy in NHS
Trusts must be able to evidence good practice in this area
Set of coordinated strategies to improve the use of antimicrobial medications with the goal to enhance patient health outcomes, reduce antibiotic resistance and decrease unnecessary costs
TARGET
Treat antibiotics reasonably, guidance, education, tools
Influences prescribers and patients to optimal antibiotic prescribing
Key principles about rational antibiotic prescribing decisions
Initial prescription
- microbial aetiology
- patient factors
- antimicrobial resistance issues
- knowledge
- guidelines- choice of agent, duration of therapy
Then
- monitoring
- test results
Review and revise
Amoxicillin
Penicillin
Used in the treatment of S. pyogenes infections, pneumococcal infections and coliform infections
- good oral bioavailability
- 20% protein binding
- metabolism not significant
- 1 hour half life
- excreted through urine
Amoxicillin mechanism of action
Inhibition of bacterial cell wall synthesis
Amoxicillin standard dose
250-1000mg 8 hourly
Amoxicillin adverse effects
Allergy
Damage to commensal microflora
Amoxicillin interactions
Can increase levels of other protein bound drugs
Beta-lactam antibiotics
Penicillin
Amoxicillin- easy oral penicillin
Flucloxacillin- for staoh aureus
Piperacillin- for pseudomonas
Beta lactam allergy
Penicillin allergy- a class effect
Immediate/ accelerated type 1
- 0-72 hours after exposure
- IgE mediated, mast cell mediated
- urticaria, wheeze, life threatening
Delayed- mixed mechanism
- > 72 hours after exposure
- will worsen with repeated dose
- dose 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
Macrolide
USed for patients with penicillin allergy for treatment of S.pyogenes, pneumococcal and coliform infections
- good oral bioavailability
- high protein binding
- hepatic metabolism
1-6 hour half life - excreted as metabolites in bile
Clarythromycin mechanism of action
Inhibition of protein synthesis in the bacterial ribosomes (50S subunit)
Clarythromycin standard dose
500mg 12 hourly
Clarythromycin adverse effets
Nausea and diarrhoea
May alter cardiac conduction- arrhythmias
Clarythromycin interactions
Inhibit enzymes (cytochrome p450 enzymes) involved in metabolism of other drugs
Vancomycin
Glycopeptide
Only against gram positive bacteria and many resistant strains including MRSA
- very low oral bioavailability
- 50% protein binding
- no metabolism
- 4-8 hour half life
- excreted in urine
Vancymycin mechanism of action
Inhibits bacterail 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
Vancymycin adverse effects
Nephrotoxic
Ototoxic
Vancymycin interactions
Other ototoxic and nephrotoxic drugs
Doxycycline
Tetracycline
Good activity against gram positive and some gram negatives and cell wall defiant bacteria
- good oral bioavailability
- moderate protein binding
- no metabolism
- 6-12 hour half life
- excreted in urine and bile
