pk.calc.half.life {PKNCA} | R Documentation |
Compute the half-life and associated parameters
Description
The terminal elimination half-life is estimated from the final points in the
concentration-time curve using semi-log regression (log(conc)~time
)
with automated selection of the points for calculation (unless
manually.selected.points
is TRUE
).
Usage
pk.calc.half.life(
conc,
time,
tmax,
tlast,
manually.selected.points = FALSE,
options = list(),
min.hl.points = NULL,
adj.r.squared.factor = NULL,
conc.blq = NULL,
conc.na = NULL,
first.tmax = NULL,
allow.tmax.in.half.life = NULL,
check = TRUE
)
Arguments
conc |
Measured concentrations |
time |
Time of the measurement of the concentrations |
tmax |
Time of maximum concentration (will be calculated and included in the return data frame if not given) |
tlast |
Time of last concentration above the limit of quantification (will be calculated and included in the return data frame if not given) |
manually.selected.points |
Have the input points ( |
options |
List of changes to the default PKNCA options (see
|
min.hl.points |
The minimum number of points that must be included to calculate the half-life |
adj.r.squared.factor |
The allowance in adjusted r-squared for adding another point. |
conc.blq |
See |
conc.na |
See |
first.tmax |
See |
allow.tmax.in.half.life |
Allow the concentration point for tmax to be included in the half-life slope calculation. |
check |
Run |
Details
See the "Half-Life Calculation" vignette for more details on the calculation methods used.
If manually.selected.points
is FALSE
(default), the
half-life is calculated by computing the best fit line for all points at or
after tmax (based on the value of allow.tmax.in.half.life
). The best
half-life is chosen by the following rules in order:
At least
min.hl.points
points includedA
lambda.z
> 0 and at the same time the best adjusted r-squared (withinadj.r.squared.factor
)The one with the most points included
If manually.selected.points
is TRUE
, the conc
and time
data are used as-is without any form of selection for
the best-fit half-life.
Value
A data frame with one row and columns for
- tmax
Time of maximum observed concentration (only included if not given as an input)
- tlast
Time of last observed concentration above the LOQ (only included if not given as an input)
- r.squared
coefficient of determination
- adj.r.squared
adjusted coefficient of determination
- lambda.z
elimination rate
- lambda.z.time.first
first time for half-life calculation
- lambda.z.n.points
number of points in half-life calculation
- clast.pred
Concentration at tlast as predicted by the half-life line
- half.life
half-life
- span.ratio
span ratio [ratio of half-life to time used for half-life calculation
References
Gabrielsson J, Weiner D. "Section 2.8.4 Strategies for estimation of lambda-z." Pharmacokinetic & Pharmacodynamic Data Analysis: Concepts and Applications, 4th Edition. Stockholm, Sweden: Swedish Pharmaceutical Press, 2000. 167-9.