Table 4.
Concentration–effect relationship parameters and mean combination index (CI) values of zanamivir and EPs® 7630 alone and in combinations for the inhibition of the bacterial VCNA.
| Compound | Concentration–Effect Parameters | CI Values at | CIwt | Combined Effect | ||||
|---|---|---|---|---|---|---|---|---|
| Dm | m | IC50 | IC75 | IC90 | IC95 | |||
| zanamivir | 17.0 ± 1 | 0.9 | - | - | - | - | - | |
| EPs® 7630 | 1.7 ± 0.1 | 1.4 | - | - | - | - | - | |
| Ratio of Zanamivir and EPs® 7630 | ||||||||
| 5:1 | 7.8 ± 0.6 | 1.1 | 1.1 | 0.7 | 0.5 | 0.4 | 0.5 | synergistic |
| 10:1 | 9.1 ± 0.4 | 1.7 | 0.9 | 0.7 | 0.6 | 0.5 | 0.6 | synergistic |
| 1:1 | 7.8 ± 0.6 | 1.7 | 2.3 | 1.8 | 1.5 | 1.3 | 1.6 | antagonistic |
| 1:5 | 1.4 ± 0.1 | 1.2 | 0.7 | 0.8 | 1.0 | 1.1 | 1.0 | additive |
| 1:10 | 1.4 ± 0.2 | 1.0 | 0.7 | 0.8 | 0.8 | 0.9 | 0.8 | moderate synergistic |
The parameters Dm (antilog of the x-intercept) and m (slope) are derived from the median effect plot and are used to calculate the CI values (n = 3–4 experiments). IC50, IC75, IC90 and IC95 are the concentrations (µg/mL) that achieve 50%, 75%, 90% and 95% inhibition of VCNA. The weighted CI (CIwt) is calculated on the basis of these representative CI values at effect levels fa > 0.5.