Table III.
Model Parameter Estimates for the Sildenafil “Reference Model” Versus the Sildenafil “Extrapolation Model” and the Bootstrap Results for both Models Based on n = 250 Resampling
| Parameter | Reference model | Extrapolation model | |||
|---|---|---|---|---|---|
| Model estimate (RSE) | Bootstrap (90 CI) | Model estimate (RSE) | Bootstrap (90 CI) | ||
|
Sildenafil clearance† CLi = CL70 kg × (WTi/70)k1 |
(CL/F)70 kg (L/h) | 113 (13%) | 112 (84.6–149) | 100 fix | 100 fix |
| k1 | 1.08 (11%) | 1.05 (0.82–1.30) | 0.874 fix | 0.874 fix | |
|
Volume of distribution† Vi = V28 kg × (WTi/28)k2 |
(V/F)28 kg (L) | 540 (33%) | 561 (311–1424) | 590 (29%) | 574 (389–1134) |
| k2 | 3.18 (10%) | 3.17 (2.41–4.27) | 3.18 (10%) | 3.16 (2.49–4.01) | |
| Absorption rate constant | ka (h−1) | 1 fix | 1 fix | 1 fix | 1 fix |
| IIV clearance | ω2 CL/F | 0.493 (14%) | 0.487 (0.363–0.631) | 0.510 (13%) | 0.512 (0.397–0.650) |
| Proportional error | σ 2 | 0.627 (7%) | 0.616 (0.538–0.703) | 0.651 (8%) | 0.646 (0.564–0.738) |
RSE is the relative standard error, and 90 CI is the 90% confidence interval representing the 5th and 95th percentiles. Interindividual and residual variability values are shown as variance estimates
†Parameters are apparent parameters, as only oral data was included