Table 2.

Population pharmacokinetic parameter estimates and bootstrap results for total testosterone in 31 healthy volunteers.

Parameter	Final model	Bootstrapa
	Estimate	Median	RSE (%)	95% CI
CL/F, kL/day	2.6	2.6	4.53	(2.42–2.8)
V/F, kL	14.4	14.4	12.1	(11.9–17.6)
Ka, $\mathrm{d}\mathrm{a}{\mathrm{y}}^{-1}$	1.22	1.22	44.9	(0.785–2.67)
${\beta }_{\mathrm{b}\mathrm{a}\mathrm{s}\mathrm{e}}$, mg/day	6.24	6.25	23.3	(3.53–8.09)
$Lambda\left(\lambda \right)$	1.18	1.43	55.9	(0.43–2.74)
$E_{\text{max}}$, mg/day	12.5	12.3	25.2	(7.75–18)
$L{H}_{50}$, IU/L	12.9	12.7	63.1	(0.892–23.7)
A_0, TC	6.24	6.21	5.82	(5.63–6.85)
${\theta }_{\mathrm{B}\mathrm{a}\mathrm{l}\mathrm{b}\mathrm{u}\mathrm{m}\mathrm{i}\mathrm{n}-\mathrm{V} }$	−1.55	−1.84	58.7	(−3.56 to −0.842)
${\theta }_{\mathrm{C}\mathrm{a}\mathrm{l}\mathrm{b}\mathrm{u}\mathrm{m}\mathrm{i}\mathrm{n}-\mathrm{V} }$	−0.27	−0.27	25.4	(−0.369 to −0.108)
${\theta }_{\mathrm{B}\mathrm{W}\mathrm{T}-\mathrm{V} }$	1.71	1.77	36.7	(0.776–2.98)
${\theta }_{\mathrm{B}\mathrm{W}\mathrm{T}-\mathrm{C}\mathrm{L} }$	0.785	0.793	17.4	(0.595–1.03)
${\theta }_{\mathrm{C}\mathrm{W}\mathrm{T}-\mathrm{C}\mathrm{L} }$	0.016	0.016	45.2	(0.00382–0.0254)
${\sigma }^2 \mathrm{a}\mathrm{d}\mathrm{d}\mathrm{i}\mathrm{t}\mathrm{i}\mathrm{v}\mathrm{e}$	0.261	0.191	105	(0.00261–0.839)
${\sigma }^2 \mathrm{p}\mathrm{r}\mathrm{o}\mathrm{p}\mathrm{o}\mathrm{r}\mathrm{t}\mathrm{i}\mathrm{o}\mathrm{n}\mathrm{a}\mathrm{l}$	0.057	0.057	18.7	(0.039–0.073)
IIV_CLb	9.66% (25.2)	8.60%	57.3	(2.98%–12.29%)
IIV_V	37% (14.6)	35.9%	52.8	(18.3%–51.7%)
IIV_Ka	53.9% (42.5)	52.4%	89.7	(0.54%–87.5%)
IIV_ $E_{\text{max}}$	45.3% (16.3)	43.1%	71.6	(14.5%–66.3%)
IIV_ $\lambda$	75.9% (25.3)	72.9%	47.4	(40.0%–99.6%)
IIV_A_0, TC	13.6% (49.6)	13.3%	77.1	(0.14%–21.3%)

CI, confidence interval; CL, clearance; E _max, maximum effect; IIV, inter‐individual variability; RSE%, percentage of relative standard error; TC, testosterone cypionate; V, volume.

^aMedian, RSE, and 95% CIs were calculated based on 500 nonparametric bootstrap results.

^bShrinkage of IIV parameters was reported along with parameter estimates.