In this episode, I’ll discuss questions 6, 7 and 8 of a recent survey of intensive care professionals about clinically relevant pharmacokinetic knowledge on antibiotic dosing. This is part 2 of a 3 part series that began with episode 414.
The survey was published in May 2019 in the journal Critical Care and titled:
Lead author: Lucas M. Fleuren
Question 6 listed 4 antibiotics: vancomycin, ceftriaxone, meropenem, and ciprofloxacin. Respondents were asked: “Which treatment goal is most relevant for these antibiotics?”
There are 3 different treatment goals for antibiotics: Peak to MIC (concentration-dependent), time spent above MIC (time-dependent), or a combination of the two referred to as the 24 hour AUC:MIC ratio.
Vancomycin and ciprofloxacin have goals that are related to the 24 hour AUC:MIC ratio, while ceftriaxone and meropenem have a treatment goal of time spent above the minimum inhibitory concentration (MIC).
This knowledge is clinically important because it can be used to decide the best way to adjust antibiotic doses when clearance is reduced. For antibiotics with time-dependent treatment goals, increase the interval between doses when clearance is reduced. And for those with AUC:MIC goals, either the dose can be reduced or the dosing interval increased. However, lowering the dose does produce the smallest decrease in AUC and may be preferred for efficacy reasons.
Question 7 presented the same 4 antibiotics and asked: “How are these antibiotics cleared?”
Vancomycin and meropenem undergo primarily renal elimination, while ceftriaxone and ciprofloxacin are eliminated renally and via the liver, bile, and feces. Knowledge of the method of elimination helps determine when a dose adjustment should be considered.
Question 8 presented a list of 5 conditions and asked: “What are risk factors for augmented renal clearance?”
- Cardiac arrest (False)
- Prolonged ICU admittance (False)
- Advanced age (False)
- Multi-trauma (True)
- Limited comorbidity (True)
For more information on augmented renal clearance and its clinical relevance check out episode 47. Members of my Hospital Pharmacy Academy have access to my in-depth practical training on augmented renal clearance which covers 2 different scoring systems and the known dose adjustments for all classes of antibiotics. For immediate access to this and over 80 other practical trainings, go to pharmacyjoe.com/academy.
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Regarding question 6, I believe it would make more sense to decrease the dose rather than increase the interval when renally adjusting time dependent antibiotics. My understanding it that it’s not necessary to give a high dose that will achieve a high peak for a time dependent medication, so giving low doses more frequently would be preferable.
https://cjasn.asnjournals.org/content/14/7/1080