Figure 1. The time course of intrathecal administered opioids (0–60 min for remifentanil [in its excipient glycine] and alfentanil, 0–120 min for morphine) and their percent maximum possible effect for analgesia assessed on the modified Hargreaves Box and their supraspinal side effects measured as increase in the supraspinal index. Each data point represents the mean +/-SEM of five to eight animals.