Sample illustration of computer-simulated CI and DRI values for paclitaxel, cisplatin, and topotecan combinations at 50, 75, 90, and 95% inhibition of 833K teratocarcinoma cell growth (for experimental data, seeTable 10) Incubation was carried out for 96 h under conditions described in Chou et al. (1994). Data analysis was carried out for parameters (Dm and m) and statistics (r) by using CompuSyn.
| Drug Combination | Combination Ratio | CI Valuesa at Inhibition of | DRI Valuesb at inhibition of | ||||||
|---|---|---|---|---|---|---|---|---|---|
| 50% | 75% | 90% | 95% | 50% | 75% | 90% | 95% | ||
| Paclitaxel + cisplatin | 1:100 | 0.887 | 0.781 | 0.690 | 0.636 | 1.89 | 2.27 | 2.72 | 3.07 |
| 2.79 | 2.94 | 3.11 | 3.22 | ||||||
| Cisplatin + topotecan | 10:1 | 0.557 | 0.562 | 0.570 | 0.577 | 3.04 | 3.23 | 3.43 | 3.58 |
| 4.39 | 3.97 | 3.59 | 3.36 | ||||||
| Paclitaxel + topotecan | 1:10 | 1.126 | 0.923 | 0.772 | 0.692 | 1.31 | 1.76 | 2.38 | 2.91 |
| 2.78 | 2.81 | 2.85 | 2.87 | ||||||
| Paclitaxel + cisplatin + topotecan | 1:100:10 | 1.150 | 0.738 | 0.480 | 0.361 | 1.87 | 3.25 | 5.65 | 8.23 |
| 2.76 | 4.22 | 6.46 | 8.63 | ||||||
| 3.98 | 5.19 | 6.77 | 8.11 | ||||||
↵ a CI values are based on the combination index isobologram equations (eq. 16 for two drugs and eq. 20 for three drugs)
↵ b DRI represents the order of magnitude (fold) of dose reduction that is allowed in combination for a given degree of effect compared with the dose of each drug alone (TC Chou, 1991; JH Chou, 1991). Upper values are for the first drug and lower values are for the second drug