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The following message was posted to: PharmPK
Dear colleagues,
I got a question about how to dosing gentamicin in a patient who has
normal serum creatinine but her UA has albumin 4+. They don't have
information on 24 hr-CrCl and there is no TDM service available in this
setting.
Does anyone have a suggestion? Any references would be much appreciated.
Thanks to all.
Best regards,
Thitima
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The following message was posted to: PharmPK
Thitima -
I would recommend that you gather more information about your
patient's past medical history -
- does she have a history of renal insufficiency?
- what is the cause of her proteinuria? is she diabetic? is it drug
induced?
- what is her estimated creatinine clearance?
Regards,
Tom
Thomas C. Dowling, PharmD, PhD
Assistant Professor
Department of Pharmacy Practice and Science
Pharmacokinetics and Biopharmaceutics Laboratory
UMAB
100 N. Penn St., Rm. 540D
Baltimore, MD 21201
410.706.0884 phone
410.706.6580 fax
410.492.9888 page
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The following message was posted to: PharmPK
Thitima,
It is hard to answer your question without patient's specific
information. I hope some following suggestions would be helpful. (I
assume you know some kinetic calculation)
. I would ask myself some questions first before using gentamicin:
Is gentamicin therapy necessary for this patient i.e. type and site
of infection, comorbid conditions, culture? What is the patient's
demographic information i.e. age, weight, height? How long the
patient will need the therapy i.e. few days or more than 1-2 weeks?
What level do you want to shoot at? What is the hemodynamic picture
of the patient?
. I ask the first question because I believe there are other
alternative therapies which could give similar result without the
risk of nephrotoxicity or ototoxicity especially in patient with
renal insufficiency or on other nephrotoxic or ototoxic drugs.
. Secondly, in some patients, particularly the elderly, cachectic,
or debilitating one, Scr levels do not truly represent creatinine
clearance. In these patients, azotemia (BUN/CR > 20) may already
indicate an early sign of renal failure after dehydration is ruled
out.
. The reasons for careful dosing of aminoglycoside are efficacy
and toxicity. For gram negative organisms, it appears
concentration-dependent. I would use once-daily dosing if the
patient is a candidate using current exclusive criteria i.e. clcr >
40ml/min, pregnancy, neutropenia, endocarditis, premature and low
birth weight neonates, etc. with level monitoring. If hemodynamic
parameters seem unstable (i.e hypotensive), two random levels about 6
hrs apart may be needed for accurate Ke estimation. If the patient
is not a candidate for ODD, the peak level should be between 4-10
(lower range for UTI, middle range for bacteremia, and higher range
for pneumonia, and the trough should be < 2.0. For gram positives,
peak between 3-5 is enough for synergy.
. Regarding nephrotoxicity, normarly it is a concern when therarpy
is more than 5-7 days. How long the patient will be on gentamicin
will shape the monitoring strategy. If tx is expected more than 10
days I would rather monitor the levels closely at the beginning to
have a good picture of the patient's Vd and Ke, and I would repeat
the levels if there is acute change in Scr (> 20% between 2
consecutive levels). Since non-oliguric renal failure is more common
than the oliguric one, I do not base mainly on urine output for renal
fxn monitoring. Periodic BUN/cr levels are needed (every 2-3 days for
the first week, 1-2 days after that) Because ototoxicity can occur
early in the tx, simple questions (if able) about hearing problems
could help to identify early signs i.e. dizziness, posture imbalance,
nystagmus, buzzing, earache, etc. Remember toxicity can occur even if
levels are therapeutic.
. The bottom line is patient focus. Current methods of Clcr
calculation (Cockroft or Jelliffe's, etc.) just give you a rough
estimation. Based on that, you calculate the initial regimen to aim
at your goal levels. Level monitoring (if needed) will give you a
better kinetic picture. And patient's condition monitoring give you a
better dynamic evaluation. "Remember, we treat the patient not the
levels or the bugs" said one of my ID doctors.
Hope this help.
Regards,
Thao Nguyen, RPh.
Clinical Pharmacist
Fresno, CA
email: tng6728.at.mediaone.net
Thao Nguyen, RPh.
Clinical Pharmacist
Community Medical Center - Fresno
Voice: 559-459-3923
Fax: 559-459-2456
Email: Tnguyen2.-a-.communitymedical.org
Tng6728.at.mediaone.netThao Nguyen, RPh.
Clinical Pharmacist
Community Medical Center - Fresno
Voice: 559-459-3923
Fax: 559-459-2456
Email: Tnguyen2.-a-.communitymedical.org
Tng6728.-a-.mediaone.net
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