The analgesic efficacy of intrathecal D-Ala2-D-Leu5-enkephalin in cancer patients with chronic pain.

Overview

D-Ala-D-Leu-enkephalin (DADL) is a pentapeptide which, compared to morphine, preferentially binds to the delta receptor. We compared the analgesic and side effects of intrathecal (i.t.) DADL and i.t. morphine sulfate (MS) in 10 tolerant cancer patients with chronic pain at or below the T12 level who were receiving inadequate relief or unacceptable side effects from systemic opiates. These patients were given i.t. DADL and i.t. MS in a randomized, double-blind, cross-over study on separate days at least 1 day apart. I.t. DADL produced analgesia in all patients tested. Total pain relief was greater with DADL than MS in 6 patients, equal in 1 patient and less with DADL in 3. Side effects, most commonly drowsiness, were similar with both MS and DADL and suggest supraspinal effects by both drugs. At the doses given i.t. DADL produced effective pain relief in patients tolerant to systemic opiates although no significant difference in analgesic efficacy between MS and DADL was observed. Studies of the relative analgesic potency of i.t. DADL in man are necessary to fully assess its value in those patients tolerant to systemic or i.t. opiates.