TABLE 2.
Parameter estimates
| Parametera | Structural model |
Final model |
||
|---|---|---|---|---|
| Estimate | Bootstrap estimate (95% CI)b | Estimate | Bootstrap estimate (95% CI)b | |
| CL (liter/h) | 5.5 | 5.5 (4.0–7.0) | 5.7 | 5.7 (5.2–6.2) |
| V (liter) | 20 | 21 (16–24) | 19 | 20 (18–21) |
| BPV | ||||
| CL (%CV) | 91 | 90 (49–130) | 74 | 70 (58–89) |
| V (%CV) | 44 | 47 (2.2–66) | 49 | 48 (38–59) |
| Correlation between CL and V (%) | 35 | 31 (10–56) | 46 | 40 (11–62) |
| Residual variability | ||||
| Proportional error (%) | 31 | 31 (22–41) | 32 | 32 (28–37) |
| Additive error (mg/liter) | 0.095 | 0.072 (0.035–0.16) | 0.056 | 0.055 (0.023–0.089) |
| Covariate effect | ||||
| CLCR on CL | 0.0091 | 0.0093 (0.0077–0.010) | ||
a
BPV, between-patient variability; CL, clearance; V, volume of distribution; CV, coefficient of variation; CLCR, creatinine clearance; CI, confidence interval.
b
Minimization was successful for both the structural and the final models, but it failed for the covariance step, yielding no estimates for the relative standard errors of the parameter estimates. Instead, a bootstrap with 1,000 replicates was done for the structural and final models to obtain 95% CIs of the parameter estimates. The shrinkages in the final model in BPV for CL and V were 8% and 29%, respectively.