Figure 1.

Illustration of individual differences in opioid requirements. Although the blood opioid concentration changes similarly after administration (arrows) and the difference between the minimal effective analgesic concentration (MEAC) (solid line) and maximum concentration with pain (MCP) (dashed line) is low among individuals, the clinical response can differ between patients because of five‐ to tenfold interpatient differences in the MEAC. Therefore, a particular opioid dose that produces satisfactory pain relief in some patients may be either too low (resulting in insufficient analgesia) or too high (resulting in adverse effects) in other patients