Vancomycin formulas

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Because there are situations where a 1 or 2compartment model may be more appropriate, both models are included in Kinetics. In general, if you are giving small doses (6mg/kg) more frequently, per the Lake and Peterson method, then the 2compartment model may be more appropriate. If you are administering larger 1520mg/kg doses over extended dosing intervals, per older dosing methods, then the 1compartment model may be more appropriate.
The vancomycin models are not hardcoded into the program. The parameters are found in the drug model database and are fully usereditable. You can tailor each drug model to fit your patient population, or you can create your own models. See the Edit drug models section of the help file for further information.
Initial dosing 1compartment population model
1. Determine maintenance dose (MD)
i. Calculate volume of distribution (Vd) Vd = 0.7 x TBW where: TBW = total body weight in kg
ii. Calculate elimination rate (kel) from creatinine clearance
Outl (outlier/Kel) model (calculates Kel) kel = CrCl x 0.0008
Norm (normal/CL) model (calculates CL) kel = (CrCl x 0.065) / Vd where CrCl = creatinine clearance
Adjust CL to IBW model CL = [Nonrenal + (NormCrCl x Renal)] x (AdjBW/TBW) where: NormCrCl = normalized creatinine clearance Nonrenal = 0 Renal = 0.065 AdjBW = LBW + (0.4 * (TBWLBW)) LBW = lean body weight in kg TBW = total body weight in kg
iii. Calculate ideal dosing interval (tau)
tau = tinf + [ (1 / kel) x ln (Cpmax/Cpmin)] where: tinf = infusion time Cpmin = Target trough Cpmax = Target peak
iv. Calculate ideal maintenance dose
MD = kel x Vd x Cpmax x tinf x (1  ekel x tau / 1  ekel x tinf)
v. User selects practical dosage and interval
vi. Calculate expected peak & trough levels
Peak = [MD / (tinf x Vd x kel)] x [(1  ekel x tinf) / 1ekel x tau)]
Trough = Peak * e kel x (tau tinf)
Initial dosing 2 compartment population model
1. Calculate dosing weight (DW) DW = LBW + [ (ABW  LBW) x CF ] where" ABW = actual weight CF is a correction factor for obesity: 40%
2. Calculate clearance (CL) from creatinine clearance CL = 0.17 + (CrCl x 0.06) where CrCl = creatinine clearance
3. Calculate ideal dosing interval (tau) tau = 6 x (72 / [ {10 * CL} + 1.9] ) where CL = vancomycin clearance
4. Calculate ideal maintenance dose The target trough level drives the dose.
5. User selects practical dosage and interval
6. Calculate expected peak & trough levels
Adjust dose 1compartment model
The methodology utilized is the same as that for aminoglycosides.
Adjust dose 2compartment model
1. Minimize Bayesian function
The Bayesian method uses populationderived pharmacokinetic parameters (ie., Vd and CL) as a starting point and then adjusts those parameters based on the serum level results taking into consideration the variability of the populationderived parameters and the variability of the drug assay procedure. To achieve that end, the least squares method based on the Bayesian algorithm estimates the parameters CL and Vd which minimize the following function:
2. Calculate ideal dosing interval Same equation as initial dosing.
3. Calculate ideal maintenance dose Same equation as initial dosing, using Bayesianderived Vd and kel.
4. User selects practical dosage and interval
5. Calculate expected peak & trough levels Same equation as initial dosing.
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