TABLE 1.
Final population PK parameter estimates of lithium in children.
| Parameter | NONMEM estimates (%RSE) | SIR median (95%CI) | CV for IIV (%RSE) | SIR median (95%CI) | Shrinkage (%) |
|---|---|---|---|---|---|
| F (%) | 100 fixed | — | 30.3 (10.9) | 30.5 (24.1–40.1) | 11.6 |
| MTT (h) | 0.52 (9.9) | 0.52 (0.40–0.71) | 65.0 (13.1) | 65.5 (50.6–85.4) | 29.6 |
| Number of transit compartment | 6 fixed | — | — | ||
| CL/F (L/h) | 0.98 (4.6) | 0.98 (0.90–1.07) | — | — | — |
| VC/F (L) | 13.1 (7.2) | 13.2 (11.7–15.2) | 26.5 (16.1) | 27.2 (17.2–37.3) | 27.1 |
| Q/F (L/h) | 0.84 (9.5) | 0.84 (0.61–1.07) | — | — | — |
| Vp/F (L) | 8.2 (17.7) | 8.3 (5.5–11.4) | 118.7 (15.4) | 118.2 (86.3–164.0) | 35.4 |
| σ | 0.091 (19.0) | 0.092 (0.076–1.11) | — | — | — |
Note: F, relative bioavailability; MTT, mean transit time. CL/F,elimination clearance; VC/F, central volume of distribution; Vp/F, peripheral volume of distribution; Q, inter-compartmental clearance; σ, additive residue error on a log scale. Population estimates in the table are given for a “typical” child with body weight of 20 kg and full maturation of metabolizing enzymes. Coefficients of variation for inter-individual variability (IIV) were calculated as 100 × (evariance)1/2. Relative standard errors (%RSE) were calculated as 100 × (standard deviation/mean). SIR: The sampling-importance resampling method. The uncertainty was derived from SIR with options of 2,000 samples and 1,000 resamples. NONMEM: nonlinear mixed effect model.