Estimates of the mean (±S.D.) apparent kinetic parameters of α-hydroxymetoprolol and O-desmethylmetoprolol formation from (R)- and (S)-metoprolol in five human liver microsomal preparations (HL 1, HL 5, HL 6, HL 7, and HL 9)
| Vmax1 | Km1 | CLint1 | Vmax2 | Km2 | CLint2 | |
|---|---|---|---|---|---|---|
| pmol/min/mg | μM | μl/min/mg | pmol/min/mg | μM | μl/min/mg | |
| α-Hydroxylation | ||||||
| (R)-Metoprolol | 12 ± 5 | 23 ± 5 | 0.58 ± 0.33 | 45 ± 11 | 1033 ± 367 | 0.05 ± 0.02 |
| (S)-Metoprolol | 16 ± 8 | 28 ± 20 | 0.65 ± 0.28 | 51 ± 31 | 714 ± 384 | 0.10 ± 0.07 |
| O-Demethylation | ||||||
| (R)-Metoprolol | 55 ± 181-150 | 20 ± 7 | 3.11 ± 1.651-150 | 1183 ± 4371-150 | 1165 ± 180 | 1.01 ± 0.29 |
| (S)-Metoprolol | 34 ± 11 | 27 ± 13 | 1.41 ± 0.57 | 1418 ± 529 | 1457 ± 354 | 1.00 ± 0.32 |
↵1-150 Value of (R)-metoprolol statistically significant different from the corresponding (S)-metoprolol value (Student's t test for paired samples;p < 0.05).