Figure 5. Isobolographic analysis for three different analgesic effects of the interaction between morphine and diclofenac at two different dose ratios. Different analgesic effects are quantified by AUC. (A) AUC 375. (B) AUC 250. (C) AUC 125. Morphine-diclofenac 1:5.66, morphine-diclofenac 1:10, as described previously. Experimental points (+/- SEM) are represented by black squares. Points on the additivity line (+/-(SEM) are theoretical. Synergy is observed at the two ratios for AUC 375 (4, P < 0.001) and only at ratio 1:10 for AUC 250 (B; P <0.05). Experimental points are not different from the additivity line for AUC 125 (C). A graphic explanation (dotted line) for A, shows that the experimental doses of each component of the combination morphine-diclofenac (ratio, 1:10) are reduced compared with the theoretical additive doses.