css: Calculate One-Compartment Model Properties

In metrumrg: Pharmacometric Tools for Data Preparation, Modeling, Simulation, and Reporting

Description

These functions calculate steady-state properties from the parameters of a one-compartment pharmacokinetic model, assuming all doses occur in the post- distribution phase (tau >> tmax).

Usage

acr(cl, v, tau, ...)
cavg(cl, tau, dose, ...)
cmax(cl, v, ka, tau, dose, ...)
cmin(cl, v, ka, tau, dose, ...)
css(cl, v, ka, tau, dose, time, ...)
ke(cl, v, ...)
tmax(cl, v, ka, tau, ...)
auc(cl, dose, ...)

Arguments

cl	apparent clearance (L/h)
v	apparent volume (L)
ka	absorption constant (h^-1)
tau	steady-state trough-to-trough interval (h)
dose	dose (arbitrary units)
time	arbitrary time point, <= tau
...	other arguments, ignored

Details

acr calculates accumulation ratio (unitless, called by css). ke calculates the elimination constant (h^-1, called by css). css calculates steady-state compartment concentration (dose units per L) at a given time. cavg calculates average concentration over dosing interval. cmin and cmax calculate minimum and maximum steady-state concentrations; they call css, passing either tau itself or tmax for the time argument. tmax calculates the time of the maximum concentration. auc calculates area under the curve.

Note that for the post-distributive assumption to hold, tau must be very large relative to the time needed for drug disposition. To the extent that it does not hold, these functions give biased results.

Value

numeric

Note

Multiple properties can be calculated within the same function or loop, since all arguments can be passed even if not needed. For example, the same five arguments can be passed, even un-named, to cmax and tmax (tmax will ignore dose). But be sure to pass by name the same arguments to cmax and cavg: the latter will ignore unused arguments but has the common arguments in a different order.

Author(s)

Tim Bergsma

References

Gibaldi M, Perrier D. Multiple dosing. Pharmacokinetics. New York: Marcel Dekker, Inc., 1982: p. 113- 144.

Examples

cavg(cl=0.05,tau=300,dose=100)
cmax(cl=0.05,v=10,ka=0.015,tau=300,dose=100)
cmin(cl=0.05,v=10,ka=0.015,tau=300,dose=100)
tmax(cl=0.05,v=10,ka=0.015,tau=300)

metrumrg documentation built on May 2, 2019, 5:55 p.m.