In this episode, I will discuss three topics regarding antibiotic dosing in CRRT (continuous renal replacement therapy).
1. Review CRRT antibiotic dosing rules
2. Review CRRT antibiotic dosing exceptions
3. Discuss the prevalence of antibiotic underdosing in CRRT
The CRRT variant this episode will refer to is CVVHDF, or continuous veno-venous hemodiafiltration as this is the only type of CRRT performed at my hospital. CVVHDF uses both convection and diffusion methods of drug and solute removal, resulting in greater drug removal than by the convection or diffusion method alone.
Much of the data for this episode comes from a paper published in Pharmacotherapy 2009 by Heintz, Matzke and Dager. Although this paper is 7 years old, it remains the reference paper for antibiotic dosing in CRRT by every tertiary drug reference I have seen. Thanks to Collin my current P4 student for confirming via literature search that this paper is still up to date!
CRRT antibiotic dosing rules
- The loading dose (if indicated) stays the same for all antibiotics in CRRT.
- If it doesn’t require renal dose adjustment, it doesn’t require adjustment for CRRT (linezolid, doxycycline, tigecycline, clindamycin, caspofungin, azithromycin, voriconazole).
- Anything with a beta lactam ring, fluroquinolones, sulfamethoxazole/trimethoprim, amphotericin B are all dosed as per normal renal function.
CRRT antibiotic dosing exceptions
- Vancomycin dose gets cut in half.
- Daptomycin either goes to q48 hour dosing or stays at q24 hour depending on how sick the patient is. If I stay on q24 hour dosing I check the CK several times per week.
- Fluconazole gets a dosing increase to 800 mg q24 hour. This always raises an eyebrow with the provider but there is even a paper that suggests 600 mg q12 hour may be needed, and after hearing this the doc usually thinks 800 mg / day is a bargain!
- The antivirals acyclovir and gangcyclovir get reduced from q8 to q12 dsoing.
- Aminoglycosides receive a traditional loading dose, then check level in 24 hours.
Since the 2009 Pharmacotherapy article was published there have been a few new antibiotics but they fit nicely within the rules I’ve described above.
- Doripenem dosing stays q8h.
- Certaroline has no data but has a beta lactam ring so I dose it as per normal renal function.
- Televancin is dosed as per normal kidneys unless flow rates are very high, then a higher dose may be needed.
Be vigilant for antibiotic underdosing in CRRT
It is very common for antibiotic doses to be renally adjusted prior to a patient starting CRRT. New initiation of CRRT should prompt a review of the patient’s antibiotic dosing, but this does not always occur. I did a retrospective review a few years ago in my hospital and found this happened about 40% of the time. There is also a paper published on this topic which describes the prevalence of underdosing antibiotics in CRRT.
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