Pharmacology of intrathecally administered agents for treatment of spasticity and pain

First Evaluation Switching From Ropivacaine to Highly Concentrated Bupivacaine in Intrathecal Mixtures for Cancer Pain

BACKGROUND

Intrathecal drug delivery is widely used for intractable cancer pain treatment. A combination of drugs with morphine and bupivacaine is recommended in first line therapy. In France, we use ropivacaine 10 mg/mL instead of bupivacaine 5 mg/mL, the only concentration available. Bupivacaine 40 mg/mL has been available in France only since July 2020 under temporary authorization of use.

OBJECTIVES

The main objective of the study was to evaluate the safety, efficacy by pain assessment, to analyze drug dosage changes, to report adverse events (AEs) and conversion ratios switching from ropivacaine to bupivacaine. Secondary objective was to evaluate costs differences.

MATERIALS AND METHODS

We conducted this retrospective follow-up monocentric study within the Institut de Cancérologie de l'Ouest (ICO) Pain Department in Angers, France. We included 14 patients aged 18 years and above, implanted with an Intrathecal Drug Delivery Systems (IDDS) for cancer pain treatment and followed up at ICO from July 2020 to February 2021 after switching from ropivacaine to bupivacaine. We used a continuous infusion mode and Bolus could be added through Personal Therapy Manager (PTM).

RESULTS

The median conversion ratio between ropivacaine and bupivacaine was 0.68 (0.65; 0.69) and resulted in no significant change in numeric rating scale evaluation (p = 0.10). We observed moderate and rapidly reversible AEs such as clinical hypotension (29%) and motor block after bolus (21%). The estimated median hospital cost per day was significantly lower (p = 0.05) for the bupivacaine refills than for the last ropivacaine pump refill, decreasing from US$ 61.7 (49.6; 70.5) to US$ 50.4 (45.9; 60.4). The median reimbursement per day from the National Health Insurance (NHI) was three times lower for bupivacaine pump refill when compared to the last ropivacaine pump refill (p < 0.01), decreasing from US$ 179.10 (156.79; 182.91) to US$ 64.59 (59.85; 71.89).

CONCLUSION

Switching from ropivacaine to bupivacaine in IDDS appears more efficacious while remaining just as secure, and at lower cost.

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.

Intrathecal Trialing of Continuous Infusion Combination Therapy With Hydromorphone and Bupivacaine in Failed Back Surgery Patients

OBJECTIVES

Intrathecal (IT) trial is a prognostic interventional pain management procedure employed to determine the potential success of treating intractable pain with an implantable infusion device system. There is a dearth of data regarding trials with continuous infusion of combination therapy (e.g. opioid combined with local anesthetic). The objective of the this study was to determine the overall outcomes of continuous infusion IT trials and factors influencing long-term success of IT therapy in patients with chronic intractable pain post-laminectomy.

MATERIALS AND METHODS

This is a retrospective analysis of all patients with lumbar failed back surgery syndrome (FBSS) who were trialed with a combination of hydromorphone and bupivacaine with a temporary externalized IT catheter from March 2007 to June 2014.

RESULTS

From a cohort of 62 patients fulfilling the inclusion criteria, 54 (87.10%) patients had successful IT trials. No significant differences were found between successful and failed trial patients with regards to age, sex, pre-trial pain numeric rating scale scores, pre-trial morphine equivalent daily dose, or trial dosages. Significant positive correlations were found between pretrial oral opioid intake and end of trial hydromorphone dose and hydromorphone dose escalation at 12 months and 24 months.

CONCLUSIONS

Patients with refractory low back pain due to FBSS who underwent successful combination IT trial with hydromorphone and bupivacaine infused through a temporary IT catheter had significantly improved pain intensity scores following permanent implant. Higher pre-trial MEDD was correlated with higher trial and post-implant opioid doses and higher rates of opioid dose escalation post-implant.

Intrathecal baclofen in patients with persistent vegetative state: 2 hypotheses

Sporadic cases of recovery from persistent vegetative state (PVS) after administration of intrathecal baclofen (ITB) have been reported without giving any possible explanation for its paradoxical effect. We summarize our recent findings on 5 patients with PVS treated with ITB and make some speculations on the mechanisms responsible for the observed clinical improvement. The patients developed spasticity and were judged eligible for ITB therapy. Two weeks after pump implantation, patients began to show a clinical improvement that, at the end of the 6 months' follow-up, was stable in all but 1 patient, ranging from a mere increased alertness to a full recovery of consciousness, as revealed by changes of the Coma Recovery Scale-Revised (CRS-R) score. Our findings suggest that ITB might favor a variable degree of clinical improvement. A proposal for a pharmacodynamic explanation of this effect has not been formally put forward. We hypothesize 2 possible mechanisms: first, a modulation confined to spinal cord segmental activities and to neuronal centripetal outputs reaching the cortex; and second, a modulation of sleep-wake cycles that, although present, may be dysregulated and interfere with alertness and awareness. Although our research is confined to a few subjects, it provides follow-up information by means of the CRS-R that is a validated standardized neurobehavioral instrument expressly designed for use in patients with PVS. Our observations indicate that further systematic investigation of the mechanisms and the putative clinical applications of ITB should be undertaken.