Table 4.
Population PK–PD parameter estimates for body sway, VAS feeling high, alertness, external perception and internal perception
| PD parameter | Population parameter estimate (RSE%) | Inter-individual variability CV% (RSE%) | Inter-occasion variability CV% (RSE%) |
|---|---|---|---|
| Body sway | |||
| Baseline (ln mm) | 5.46 (1.26) | 6.66 (24.3) | 3.00 (32.2) |
| Emax (log mm) | 0.829 (24.5) | 68.8 (40.2) | – |
| EC50*(ng ml−1) | 7.24 (42.8) | – | – |
| Ke0 (h−1) | 0.466 (17.9) | 73.4 (33.6) | – |
| IC50 (ng ml−1) | 22.0 (45.2) | – | – |
| Residual variability (SD of additive error) | 0.212 (10.5) | – | – |
| Feeling high | |||
| Baseline (log mm) | 0.321 (3.96) | 21.6 (38.5) | – |
| Emax (log mm) | 0.713 (31.6) | 124 (39.6) | – |
| EC50* (ng ml−1) | 6.98 (33.5) | – | – |
| Ke0 (h−1) | 1.04 (17.4) | 71.6 (32.4) | – |
| IC50 (ng ml−1) | 30.5 (61.6) | – | – |
| Maximum inhibition | 0.751 (20.6) | – | – |
| Residual variability (SD of additive error) | 0.254 (19.1) | – | – |
| Alertness | |||
| Baseline (mm) | 49.4 (1.10) | 5.13 (47.9) | 180 (37.0) |
| Slope (ng−1 ml−1) | 0.547 (45.2) | 98.1 (53.5) | – |
| Ke0 (h−1) | 0.347 (33.7) | 4.64 (26.0) | – |
| IC50 (ng ml−1) | 33.6 (45.8) | – | – |
| Residual variability (SD of additive error) | 3.30 (18.3) | – | – |
| External perception | |||
| Baseline (log mm) | 0.367 (0.529) | – | 3.86 (46.1) |
| Slope (ng−1 ml−1) | 0.00258 (41.9) | 154 (29.4) | – |
| Ke0 (h−1) | 0.868 (16.9) | 69.9 (30.1) | – |
| IC50 (ng ml−1) | 37.1 (59.6) | – | – |
| Residual variability (SD of additive error) | 0.0182 (19.1) | – | – |
| Internal perception | |||
| Baseline (log mm) | 0.366 (0.508) | 2.68 (68.2) | 1.46 (36.9) |
| Slope (ng−1 ml−1) | 0.000869 (38.2) | 151 (35.1) | – |
| Ke0 (h−1) | 0.955 (20.1) | 71.4 (45.5) | – |
| IC50 (ng ml−1) | 58.8 (44.2) | – | – |
| Residual variability (SD of additive error) | 0.0123 (22.8) | – | – |
*
EC50 of THC effect. CV, coefficient of variation (%); EC50, concentration producing 50% of Emax; Emax, maximal effect; IC50, concentration producing 50% of inhibition of THC Emax; Ke0, effect compartment equilibration rate constant; RSE, relative standard error (%); SD, standard deviation.