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Potency ratios (observed/predicted additive) for binary mixtures of cocaine and caffeine (top row), MDPV and caffeine (middle row), and cocaine and MDPV (bottom row) at three different effect levels: 20% (left column), 50% (center column), and 80% (right column). Potency ratios for individual subjects are depicted by their ID no. The group mean and 95% CI are depicted by the vertical gray line and error bars, respectively.
