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Vancomycin - Single Level Analysis [Advanced version]

Patient:     Location:
Drug:   
Patient Age (yrs):   ?        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]
Desired peak:  mcg/ml   Desired trough:    mcg/ml
Select Vd Method: 
Volume of distribution
:   L/kg   
Range: 0.5 - 0.95 (Usual: 0.7 L/kg)

Background

Ambrose-Winter’s Single Trough Method
Principles:
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.

Ambrose-Winter’s volume of distribution equation:
where Vd (L) = (0.17 × [age in years]) + (0.22 × [TBW in kg]) + 15
           (Note: TBW even if obese)

Reference

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

Disclaimer

All calculations must be confirmed before use. The authors make no claims of the accuracy of the information contained herein; and these suggested doses are not a substitute for clinical judgement. Neither GlobalRPh Inc. nor any other party involved in the preparation of this program shall be liable for any special, consequential, or exemplary damages resulting in whole or part from any user's use of or reliance upon this material.PLEASE READ THE DISCLAIMER CAREFULLY BEFORE ACCESSING OR USING THIS SITE. BY ACCESSING OR USING THIS SITE, YOU AGREE TO BE BOUND BY THE TERMS AND CONDITIONS SET FORTH IN THE DISCLAIMER.   Read the disclaimer
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