﻿ Vancomycin formulas
 Vancomycin formulas
 Because there are situations where a 1- or 2-compartment 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 2-compartment model may be more appropriate.  If you are administering larger 15-20mg/kg doses over extended dosing intervals, per older dosing methods, then the 1-compartment model may be more appropriate.   The vancomycin models are not hard-coded into the program.  The parameters are found in the drug model database and are fully user-editable.  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 1-compartment 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   Outlier (Kel) model (calculates Kel) kel = CrCl x 0.0008   Normal (CL) model (calculates CL) CL = (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 * (TBW-LBW)) LBW = lean body weight in kg TBW = total body weight in kg   iii.  Calculate ideal dosing interval (tau)   tau = tinf + [ (-1 / kel) x ln (CpTmax/CpTmin)] where: tinf = infusion time CpTmin = Target trough CpTmax = Target peak   iv.   Calculate ideal maintenance dose   MD = kel  x  Vd  x CpTmax  x  tinf  x  (1 - e-kel x tau / 1 - e-kel x tinf)   v.  User selects practical dosage and interval   vi.  Calculate expected steady-state peak & trough levels           CpSSmax = [MD / (tinf x Vd x kel)] x [(1 - e-kel x tinf) / 1-e-kel x tau)]   CpSSmin =   CpSSmax * 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 1-compartment model   The methodology utilized is the same as that for aminoglycosides.     Adjust dose 2-compartment model   1.   Minimize Bayesian function   The Bayesian method uses population-derived 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 population-derived 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 Bayesian-derived Vd and kel.   4.   User selects practical dosage and interval   5.   Calculate expected peak & trough levels Same equation as initial dosing.   See also: Introduction Monitoring parameters Precautions Bibliography
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