The system and method for predicting and measuring a subject's analgesic state and analgesic adequacy. Biopotential signals are obtained from a subject through electrodes. A processor will compute a measure that is representative of the subject's sedative state and/or muscle activity. A metric representative of such measures is then determined. In the case where a measure is taken of both the subjects’ sedative state and muscle activity the two measures are combined into an index representative of the subject's analgesic state and analgesic adequacy.
