TABLE 1.
Inhibition of xenobiotic-metabolizing P450 isoforms by t-CA
IC50 values are the mean of at least three experiments conducted on separate days. Values in parenthesis represent the 95% confidence interval (lower limit–upper limit).
| P450 Isoform | IC50 | N | Fold Difference Compared with CYP2A6 |
|---|---|---|---|
| µM | |||
| 2A6 | 6.1*** (2.9–12.7) | 15 | — |
| 1A2 | 106.3 (68.5–164.8) | 12 | 17.4 |
| 2B6 | 107.3 (88.3–130.3) | 12 | 17.6 |
| 2C9 | 96.2 (57.0–162.5) | 9 | 15.8 |
| 2C19 | 212.8(132.7–349.2) | 9 | 34.9 |
| 2D6 | > 2000a | 9 | Not determined |
| 2E1 | 64.0 (56.9–71.9) | 8 | 10.5 |
| 3A4 | 116.1 (51.1–263.0) | 9 | 19.0 |
a
Fifty percent inhibition was only observed at concentrations ≥2000 µM; the IC50 for quinidine (positive control) was <1 µM (N = 9).
***
P < 0.001 in the comparison of logIC50 for CYP2A6 to logIC50 for CYP1A2, 2B6, 2C9, 2C19, 2E1, and 3A4.