Fig. 2. Isobologram at the 50% maximum effective dose (ED⁵⁰) level of the interaction between intrathecal adenosine and T62. The value for the ED⁵⁰(and their 95% confidence limits) for each agent alone are depicted on the axes, with the line between them representing the line of additivity. The value for the ED⁵⁰of the combination does not differ significantly from the theoretical additive point.