Figure 1. The daily consumption of oral morphine on day 15 was as follows: control group (CG) = dipyrone group (DG) = nitroglycerin group (NG) (P > 0.05); DG = NG = ketamine group (KG) (P > 0.05); CG > KG (P = 0.036). On day 20, the morphine consumption was CG = DG (P = 0.873); CG > NG = KG (P < 0.02) (CG > KG, P = 0.004; CG > NG, P = 0.0183); DG = NG (P = 0.10); DG > KG (P = 0.04). On day 30, the oral morphine consumption was CG = DG (P = 0.815); CG > KG (P = 0.003); CG > NG (P = 0.012); DG > NG (P = 0.021); DG > KG (P = 0.001); KG = NG (P = 0.964). M = Morphine. *P < 0.05.