COGNITIVE AND MOTOR FUNCTION IMPAIRMENTS DURING CONTINUOUS OPIOID ANALGESIC INFUSIONS

Morphine and other opioid analgesics may interfere with normal cogniti on and motor function during long-term treatment of cancer-related pai n. In this study, we used individually tailored steady-state drug infu sions to control plasma concentrations of morphine and alfentanil and measured the extent of cognitive and motor impairments produced by eac h drug in healthy volunteers. The tailored infusions allowed evaluatio n of cognitive and motor effects at three sequential, steady plasma co ncentrations of each opioid. During continuous infusion, both drugs ca used significant, plasma concentration-related impairments of ability to process serially-presented information and of fine motor control at plasma drug concentrations within the usual therapeutic range. We fou nd significant relationships between cognitive and motor function decr ements and plasma opioid concentration with both morphine and alfentan il. We conclude that magnitudes of cognitive and motor function impair ments are equivalent for these two mu receptor selective agonists at e quianalgesic plasma concentrations.