CP3-5 antibacterial concepts and antibiotics Flashcards
What is the minimum inhibitory concentration?
The minimum amount of antibiotic that inhibits bacteria growing
What needs to be considered alongside minimum inhibitory concentration?
Serum concentrations of antibiotics
How is susceptibility of an antibiotic tested?
By working out the minimum inhibitory concentration
What is the pharmodynamic target?
Where the action of the drug/antibiotic has an optimal antibiotic concentration and efficacy relationship.
What is the aim of antibiotic dosage?
To achieve the pharmodynamic target without needing any more or any less drug
Why must antibiotic dosage consider pharmokinetic variation?
As there is lots of variation between patients and how drugs are distributed in, and cleared from, the body which affects efficacy of a dose.
What is the probability of target attainment?
The probability that if treated with a certain dose of antibiotic, for a certain infection that a patient will attain the desired pharmodynamic target.
What are characteristics of oral antibiotics?
Slower absorption than IV
Associated diarrhoea
Absorbed in small bowel
Absorption varies among individuals
No IV access required so no IV related side effects
Can be self administered
Cheaper than IV antibiotics
What are characteristics of IV antibiotics?
Faster/instantaneous absorption compared to oral
Associated diarrhoea
No bowel needed for absorption
Absorption rate varies amongst individuals
IV access required so associated side effects e.g. thrombosis or infection
Medical staff required for administration
More expensive than oral antibiotics
What is something to consider when a current dose isn’t effective?
Whether increasing dose increase risk of drug toxicity for the patient and if continuation on the same dose for longer would be more beneficial
Fill in the blanks
Once in systemic circulation, efficacy of IV antibiotics is ___________ oral antibiotics.
Equal to
Why might a drug be given via IV rather than orally?
Drug only available intravenously
Drug not well absorbed orally
IV antibiotic may quickly and reliably target serum antibiotic concentration
In what infections are oral and IV antibiotics shown to be comparable in efficacy?
- bone and joint infections
- pyelonephritis
- empyema (lung abscesses)
- febrile neutropenia in cancer patients
What is oral bioavailability?
The percentage of an oral antibiotic that reaches the blood stream
How can blood dose of an antibiotic be made equal for IV and oral?
By adjusting dose based on oral bioavailability e.g. ciprofloxacin IV dose is 400mg 12 hourly. Oral bioavailability is 80% so oral dosage is 500mg 12 hourly.
