Vancomycin - Single Level Analysis

Patient:     Location:
Drug:    Weight:  
Current dose being given mg    Current dosing interval: hrs
Current infusion time (hrs):

Single level drawn - Trough

Trough level obtained:   mcg/ml
When was the trough drawn?:
Enter number of hours before next dose:   hrs
[Hint:   0.01 = <1 minute before next dose.   0.08 = ~5 minutes before next dose]

 If you would like to enter the time since the last dose was given, use this version.new
This new version may be especially useful if the trough was drawn late and the
next dose was delayed. Example: current regimen vanco 1 gram q12h.  Trough was
drawn 12.5 hours after the last dose.
Desired peak:  mcg/ml   Desired trough:    mcg/ml


A new program was created to determine when to administer the next dose of vancomycin after a supratherapeutic trough is obtained.  An estimated elimination rate constant is generated from the creatinine clearance which is then used to determine the timing of the next dose based on the desired target trough concentration.

I also updated our current trough calculator to also generate an estimated vancomycin kel value based on the creatinine clearance.  Use this program if the vancomcyin level is drawn early and you want to estimate the actual trough just before the next dose to determine if the current regimen is appropriate - link to new program.)


Ambrose-Winter’s Single Trough Method
A population Vd is used to estimate the [Peak].
This calculated [Peak] and measured [Trough] are then used to calculate an elimination rate constant (kel).

[Peak]=measured [Trough] + Dose/Vd
kel = ln ([Peak]/[Trough])/Tau
Infusion equations are then used to calculate a new Tau and Dose.

Side note: the GlobalRPh calculator uses the Vd recommended in Bauer's text: 0.7 L/kg.
    Use the advanced version if you wish to manipulate this value.


Ambrose PJ, Winter ME. In: Winter ME. Basic clinical pharmacokinetics, 4th ed. Philadelphia: Lippincott Williams & Wilkins; 2004:451-76.

Alternate expression of kel equation:
single level

Normally kel = (Ln C1 / C2) / (t2 - t1)
C1= actual or extrapolated Peak; or post peak level
C2= actual or extrapolated trough; or random level
Drawn at least 1.5 x estimated half-life after first level.
(t2 - t1) = Time difference between levels.

Equation 15.5 page 455:
cmax =  [cmin + dose (s) (f)] / Vd


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