Table 1.
P-gp inhibitory potential (IC50 values) based on rhodamine 123 accumulation assay.
| Drug | IC50 (µM) (Rhodamine 123) 1 | IC50 (µM) (Digoxin) 2 | Ratio IC50 Rhodamine 123/IC50 Digoxin | IC50 Range for P-gp Inhibition (-fold) 3 |
|---|---|---|---|---|
| Amiodarone | 22.9 ± 2.0 | 9.6 | 2.4 | 27 |
| Carvedilol | 3.4 ± 1.2 | 1.3 | 2.7 | 168 |
| Cyclosporin A | 4.8 ± 1.1 | 1.1 | 4.4 | NR 4 |
| Diltiazem | 11.7 ± 2.2 | 4.6 | 2.6 | 76 |
| Elacridar | 0.05 ± 0.01 | 0.03 | 1.9 | NR |
| Felodipine | 127.3 ± 6.0 | 4.2 | 30.3 | 188 |
| Isradipine | 83.1 ± 10.8 | 7.7 | 10.8 | 24 |
| Itraconazole | No inhibition 5 | 1.8 | NA 6 | NR |
| Mibefradil | 4.7 ± 1.8 | 1.9 | 2.5 | 48 |
| Nicardipine | 19.4 ± 1.5 | 3.8 | 5.1 | 78 |
| Nitrendipine | 250.5 ± 43.8 | 18.2 | 13.8 | 72 |
| Quinidine | 51.3 ± 1.5 | 4.9 | 10.5 | 98 |
| Sertraline | No inhibition 5 | 12.9 | NA | 18 |
| Troglitazone | 44.1 ± 7.7 | 15.9 | 2.8 | 36 |
| Verapamil | 14.3 ± 1.4 | 2.8 | 5.1 | 796 |
| Zosuquidar | 0.18 ± 0.12 | 0.02 | 9.7 | NR |
1 expressed as mean ± SEM of three independent assays; 2 data from Poirier et al. [41]; 3 corresponds to the ratio of the highest versus lowest IC50 values determined from five experimental measurements based on digoxin transport and vesicle uptake of P-gp substrates, according to Lee et al. [11]; 4 NR, not reported; 5 no inhibition at 100 µM; 6 NA, not applicable.