Effects of Bupivacaine on Opioid Patient-Controlled Intrathecal Analgesia in Chronic Pain Patients Implanted with Drug Delivery Systems.

BACKGROUND: Combining neuraxial opioids and local anesthetics in acute pain results in improved duration of analgesia and reduced dosages and adverse effects. Although commonly used in intrathecal drug delivery systems (IDDS) for chronic pain, the effectiveness of this admixture has not been examined specifically in relation to patient-controlled intrathecal analgesia (PCIA). METHODS: IDDS-implanted chronic noncancer pain patients receiving opioids with bupivacaine (O + B) were randomized to receive either opioids without bupivacaine (O) or O + B in a double-blind manner, at IDDS refills, for one week and then crossed over to the other solution for another week. Primary outcome measures included numeric rating scale (NRS) pain scores before and within 30 minutes after PCIA boluses. Secondary outcome measures included average NRS scores and functional outcome measures. RESULTS: Seventeen patients were enrolled, and 16 patients completed the study. There were no differences in NRS scores before and after PCIA boluses between the O and O + B conditions, though pain scores improved significantly (average decrease in NRS scores: O 1.81 ± 1.47 vs O + B 1.87 ± 1.40, P = 0.688). No differences were noted in speed of onset or duration of analgesia. Although more patients subjectively preferred the O + B treatment, the difference was not statistically significant. No differences were noted in secondary outcome measures, with the exception of global impression of change having higher scores in O compared with O + B. CONCLUSIONS: Acutely removing bupivacaine from a chronic intrathecal infusion of opioids and bupivacaine in patients with chronic noncancer pain did not adversely affect PCIA effectiveness, nor did it affect speed of onset or duration of effect. These findings are divergent from those in acute pain and may have to do with study conditions and pain phenotypes.