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
Macrolides e.g. clarithromycin
Enhance anticoagulant effect
Increases plasma phenytoin concentrations
Increase plasma digoxin concentrations
- Side effect - Diarrhoea
Trimethoprim
Hyperkalaemia with ACE inhibitors
Nephrotoxicity with cyclosporin
- Side effect - Erythema multiforme
Glycopeptides e.g. teicoplanin
Increased nephrotoxicity with aminoglycosides
Loop diuretics
- Side effect - nephrotoxicity + red man syndrome
Linezolid
Serotonin syndrome
- Side effect - Optic neuropathy, Blood disorders
Aminoglycosides
Ototoxicity with frusemide
- Side effect - Ototoxicity, Nephrotoxicity
Amoxicillin-clavulanic acid SIDE EFFECT
Cholestatic jaundice
Side effects of all antibiotics
Antibiotic associated diarrhoea, clostridium difficile infection
Metronidazole side effect
Disulfiram reaction with alcohol
Penicillin allergy
- 10% of people
- Patients may react to other beta-lactam antibiotics
Limitations of antibiotics
Will not treat non-infectious diseases/ contaminated samples
Antibiotics may only be the supporting actor in some infections that require surgical intervention
They all damage an individual’s microbiome
