Fig 1.
Theoretical isobologram, curve shift, and combination index analyses of drug–drug interactions.
Antagonistic relationships require increased dosage of drugs for the same individual effects, additive effects require the same dosage of drugs for the same individual effects, and synergistic interactions require decreased dosage of drugs for the same individual effects. (A) Isoboles connect the points of EC50 of each drug, A and B. If the drugs are synergistic, the EC50 of agent A in the presence of B should be lower than that of agent A alone. (B) Curve shift analysis reveals a leftward shift, indicating synergy, or a rightward shift, indicating antagonism. This corresponds to changes of EC50. (C) CI values less than, equal to, or greater than 1 indicate synergy, additivism, or antagonism, respectively. Images created with BioRender.com. CI, combination index; EC50, half maximal effective concentration.
Table 1.
Additive and synergistic drug combination strategies assessed against multiple eukaryotic pathogens.