Figure 3. Time to first use of intravenous morphine expressed in minutes (means +/- SD) as assessed by the use of the patient-controlled analgesia pump in patients (n = 10 for each group) given intra-articular saline, neostigmine (125, 250, or 500 micro gram), morphine (2 mg), or subcutaneous neostigmine (500 micro gram). A significant difference (P <0.05) between intra-articular groups and intra-articular saline is marked by an asterisk, and differences between groups and 500 micro gram neostigmine given subcutaneously is indicated by #.