Table 1.

Relationship between the combination index values and the mode of drug interaction

Range of CI values	Mode of drug interaction
< 0.1	Very strong synergism
0.1–0.3	Strong synergism
0.3–0.7	Synergism
0.7–0.85	Moderate synergism
0.85–0.90	Slight synergism
0.90–1.10	Nearly additive
1.10–1.20	Slight antagonism
1.20–1.45	Moderate antagonism
1.45–3.3	Antagonism
3.3–10	Strong antagonism
> 10	Very strong antagonism

CI combination index