antibiotic concepts Flashcards
how are bacterial infections treated?
with antibiotics to inhibit bacterial growth
how do we test how susceptible an antibiotic is to a bacteria?
we determine the minimum amount of antibiotic that stops the bacteria from growing - minimum inhibitory concentration
what is the MIC?
it is the minimum concentration of antibiotic that inhibits bacterial growth in a standard culture media and standard bacteria inoculum
what is the only variable in MIC tests?
the concentration of AB
how are ABs dosed?
to ensure that all patients get blood concentrations of ABs that are associated with increased survival - pharmacodynamic target
what happens if the AB exceeds the PD target?
there is no additional efficacy benefit
what characteristics does the MIC have?
measurable, important and variable
what needs to be considered with AB doses?
the intraspecies variation in MIC values - the bacterial population and its variations and the serum concentrations of ABs
what three factors are important for AB cure?
human populations and the variation within it, the MIC and the antibiotic pharmacokinetics
where is there variation in the antibiotic concentration profiles?
in how it is distributed around the body and cleared from the body
what are simulations?
they are statistical analyses that predict the optimal antibiotic dose. They determine the probability that if a patient was to be treated with a certain AB for a certain infection, that they would attain the desired pharmacodynamic target - know as the probability of pharmacodynamic target attainment - determine what dose of AB will achieve a high PTA
when can the target dose be used to treat?
if it has an acceptable toxicity profile - patients must get just enough
why are some drugs only available IV?
They are not absorbed well orally and they may be required to quickly and reliable achieve the targeted serum AB concentration
in what infections are oral and IV ABs comparable?
joint and bone infections, pyelonephritis, empyema, febrile neutropenia
what are the benefits of PO?
no IV access is required, therefore no side effects from this access, there is self administration and is cheaper - also once it has reached systemic circulation it is considered as equal efficacy to IV
what are the disadvantages of PO?
slower absorption, absorption may vary, antibiotic associated diarrhoea, required the small bowel for absorption
what are the benefits of IV?
it is faster or instantaneous absorption, and the staff can vary the absorption rate. No small bowel is required for absorption and it reached the targeted serum concentration quicker and reliably
what are the disadvantages of IV?
antibiotic associated diarrhoea, no benefit over PO once in systemic circulation, IV access required and there are side effects with this such as thrombophlebitis, thrombosis and infection, medical staff are required for administration and is more expensive
what are AB durations?
short or long course for all depending on clinical response and it is biomarker driven
what does the choice of course depend on?
the evidence, social and clinical factors, costs and resources available
what needs to be balanced in AB duration?
maximising the cure whilst minimising adverse events - there is a positive correlation between duration and number of adverse events and a negative correlation between failure rates and duration
when should antibiotics be started?
when the benefits of giving them outweigh the disadvantages - always in a patient with sepsis - start early and stop early
what are two methods of administering antibiotics?
start narrow and look to broaden asap
start broad and look forward to when to narrow
what affects when ABs are given?
patient factors, plan for other treatments and overall management plans, delayed with plan when to, when there is no sign of infection such as in autoimmune inflammation
