calc_derived: Calculate derived pharmacokinetic parameters for a 1-, 2-, or...

In pmxTools: Pharmacometric and Pharmacokinetic Toolkit

Calculate derived pharmacokinetic parameters for a 1-, 2-, or 3-compartment linear model.

Description

Calculate derived pharmacokinetic parameters for a 1-, 2-, or 3-compartment linear model.

Usage

calc_derived(..., verbose = FALSE)

calc_derived_1cpt(
  CL,
  V = NULL,
  V1 = NULL,
  ka = NULL,
  dur = NULL,
  tlag = NULL,
  tinf = NULL,
  dose = NULL,
  tau = NULL,
  step = 0.1,
  type = "all",
  sigdig = 5
)

calc_derived_2cpt(
  CL,
  V1 = NULL,
  V2,
  Q2 = NULL,
  V = NULL,
  Q = NULL,
  dur = NULL,
  tinf = NULL,
  ka = NULL,
  tlag = NULL,
  dose = NULL,
  tau = NULL,
  step = 0.1,
  type = "all",
  sigdig = 5
)

calc_derived_3cpt(
  CL,
  V1 = NULL,
  V2,
  V3,
  Q2 = NULL,
  Q3,
  V = NULL,
  Q = NULL,
  ka = NULL,
  dur = NULL,
  tinf = NULL,
  tlag = NULL,
  dose = NULL,
  tau = NULL,
  step = 0.1,
  type = "all",
  sigdig = 5
)

Arguments

...	Passed to the other calc_derived_*() functions.
verbose	For calc_derived(), provide a message indicating the type of model detected.
CL	Clearance (volume per time units, e.g. L/h)
V1, V	Central volume of distribution (volume units, e.g. L). Values are synonyms; use only one.
ka	Absorption rate (inverse time units, e.g. 1/h)
dur	Duration of zero-order absorption (time units, e.g. h)
tlag	Absorption lag time (time units, e.g. h)
tinf	Duration of infusion (time units, e.g. h)
dose	Dose (amount units, e.g. mg)
tau	Duration of interdose interval (time units, e.g. h; defaults to 24)
step	Time increment to use when estimating NCA parameters (time units, e.g. h; defaults to 0.1)
type	Parameters to return. Default is "all". If not "all", this may be a vector from the names of the return value list.
sigdig	Number of significant digits to be returned. Default is 5.
V2	First peripheral volume of distribution (volume units, e.g. L)
Q2, Q	Intercompartmental clearance from central to first peripheral compartment (volume per time units, e.g. L/h). Values are synonyms; use only one.
V3	Second peripheral volume of distribution (volume units, e.g. L)
Q3	Intercompartmental clearance from central to second peripheral compartment (volume per time units, e.g. L/h)

Value

Return a list of derived PK parameters for a 1-, 2-, or 3-compartment linear model given provided clearances and volumes based on the type. If a dose is provided, estimated non-compartmental analysis (NCA) parameters will be provided as well, based on simulation of single-dose and (if tau is specified) steady-state time courses.

• Vss: Volume of distribution at steady state, V_{ss} (volume units, e.g. L); 1-, 2-, and 3-compartment

• k10: First-order elimination rate, k_{10} (inverse time units, e.g. 1/h); 1-, 2-, and 3-compartment

• k12: First-order rate of transfer from central to first peripheral compartment, k_{12} (inverse time units, e.g. 1/h); 2- and 3-compartment

• k21: First-order rate of transfer from first peripheral to central compartment, k_{21} (inverse time units, e.g. 1/h); 2- and 3-compartment

• k13: First-order rate of transfer from central to second peripheral compartment, k_{13} (inverse time units, e.g. 1/h); 3-compartment

• k31: First-order rate of transfer from second peripheral to central compartment,k_{31} (inverse time units, e.g. 1/h); 3-compartment

• thalf_alpha: t_{1/2,\alpha} (time units, e.g. h); 1-, 2-, and 3-compartment

• thalf_beta: t_{1/2,\beta} (time units, e.g. h); 2- and 3-compartment

• thalf_gamma: t_{1/2,\gamma} (time units, e.g. h); 3-compartment

• alpha: \alpha; 1-, 2-, and 3-compartment

• beta: \beta; 2- and 3-compartment

• gamma: \beta; 3-compartment

• trueA: true A; 1-, 2-, and 3-compartment

• trueB: true B; 2- and 3-compartment

• trueC: true C; 3-compartment

• fracA: fractional A; 1-, 2-, and 3-compartment

• fracB: fractional B; 2- and 3-compartment

• fracC: fractional C; 3-compartment

• AUCinf: Area under the concentration-time curve to infinity (single dose)

• AUCtau: Area under the concentration-time curve over the dosing interval at steady state

• Cmax: Maximum concentration after a single dose

• Cmaxss: Maximum concentration over the dosing interval at steady state

• Tmax: Time after dose of maximum concentration

• AUCinf_dose_normalized: Dose-normalized area under the concentration-time curve to infinity (single dose)

• AUCtau_dose_normalized: Dose-normalized area under the concentration-time curve over the dosing interval at steady state

• Cmax_dose_normalized: Dose-normalized maximum concentration after a single dose

• Cmaxss_dose_normalized: Dose-normalized maximum concentration over the dosing interval at steady state

• step: Time increment used when estimating NCA parameters.

The input parameters with standardized names (dose, V1, V2, V3, CL, Q2, and Q3) are also returned in the list, and if provided, additional PK parameters of ka, tlag, tinf and dur are also returned in the list. All inputs may be scalars or vectors.

Author(s)

Justin Wilkins, [e-mail]

Bill Denney, [e-mail]

References

Shafer S. L. CONVERT.XLS

Rowland M, Tozer TN. Clinical Pharmacokinetics and Pharmacodynamics: Concepts and Applications (4th). Lippincott Williams & Wilkins, Philadelphia, 2010.

Examples

params <- calc_derived(CL=29.4, V1=23.4, V2=114, V3=4614, Q2=270, Q3=73)
params <- calc_derived_1cpt(CL=16, V=25)
params <- calc_derived_2cpt(CL=16, V1=25, V2=50, Q=0.5)
params <- calc_derived_3cpt(CL=29.4, V1=23.4, V2=114, V3=4614, Q2=270, Q3=73)

pmxTools documentation built on Aug. 25, 2025, 5:12 p.m.