Antibacterial concepts Flashcards
How is bacteria tested to see how susceptible it is to antibiotic
- MIC - minimum inhibitory concentration
- MIC varies between species
- minimum conc of antibiotic that inhibits bacterial growth
What is pharmacodynamic target
- For all antibiotics there is a PD
- After value is achieved there is no benefit to increasing dose - would cause toxicity
- Fixed target
What is PTA
Probability of reaching the desired PD target
How is PTA determinesd
- Simulations determine what dose of antibiotic will achieve a high PTA without toxicity
Oral antibiotics properties
- Slower absorption
- Requires small intestine
- Absorption may vary
- No IV access needed
- No IV side effects
- Self administration
- Cheaper
IV antibiotics properties
- Faster absorption
- No bowel needed
- Absorption rate varies
- IV access required
- IV side effects such as infection, thrombosis
- Medical staff needed
- More expensive
Antibiotic durations
- Chosen to maximise cure while minimising adverse events
- As durations increase, adverse events increase but failure rate decreases
When to start antibiotics
- Sepsis
- benefits greater than disadvantages
- DO NOT when no sign of infection
Benefits of early antibiotic therapy
- Lower mortality and morbidity and prevents infection metastases
Disadvantages of early antibiotic therapy
- Reduces chances of target therapy
- Insufficient time to check allergies
Therapeutic drug monitoring
- Used to increase efficacy and prevent toxicity for drugs like glycopeptises
Therapeutic window
- The range within which there is a high probability of PTA
Surgical antibiotic prophylaxis
- Good levels of Ab in skin before surgical incision - stops cellulitis of wound
Penicillins/Beta-lactams e.g. amoxicillin
Limited interactions
Reduces excretion of methotrexate
- Side effect - allergic reactions
Quinolones e.g. ciprofloxacin
Alters phenytoin concentrations
- Side effect - Tendonitis
