Figure 3. Isobologram for the intrathecal interaction of midazolam and AP-5. Horizontal and vertical bars indicate SEM. The oblique line between the x-axis and y-axis is the theoretic additive line. The point in the middle of this line is the theoretic additive point calculated from the separate ED⁵⁰values. The experimental point lies far below the additive line, indicating a significant synergism.