Chemical Stability of an Admixture Combining Ziconotide and Bupivacaine During Simulated Intrathecal Administration

Physicochemical Stability Study of the Morphine-Bupivacaine-Ziconotide Association

OBJECTIVE

The aim of this study was to investigate the physicochemical stability of morphine-bupivacaine-ziconotide mixtures used in intrathecal analgesia in polypropylene syringes and intrathecal pumps.

MATERIALS AND METHODS

The stability study method was conceived according to International Council for Harmonisation guidelines. For propylene syringes, six different mixtures of morphine-bupivacaine and ziconotide were assessed over seven days. Two storage temperatures were tested (5 °C ± 3 °C and 25 °C ± 2 °C). For implantable pumps, nine different mixtures were assessed over 60 days and stored at 37 °C. Assays were performed using ultrahigh-pressure liquid chromatography. Turbidity and pH also were measured throughout the study.

RESULTS

Results confirmed excellent physicochemical stability for morphine and bupivacaine in the study for all conditions investigated (pumps at 37 °C, polypropylene syringes at 5 °C ± 3 °C and 25 °C ± 2 °C). Concerning ziconotide, after seven days, our study showed that every 95% confidence interval calculated had lower bounds >90% for all mixtures stored in polypropylene syringes. In implantable pumps, a decrease of the concentration was observed in all the mixtures studied. Moreover, the appearance of a degradation product confirmed the ziconotide degradation.

CONCLUSION

All results are in favor with a physicochemical stable preparation for six mixture profiles when stored in polypropylene syringes at 5 °C ± 3 °C and 25 °C ± 2 °C. For mixtures stored in implantable pumps, the efficacy should decrease over time owing to the degradation of ziconotide. A trade-off between high morphine concentration and increased refill interval will need to be found by clinicians.

Physicochemical Stability Study of the Morphine-Ropivacaine-Ziconotide Association in Implantable Pumps for Intrathecal Administration

PURPOSE

This study aimed to investigate the physicochemical stability of morphine-ropivacaine-ziconotide mixtures used in intrathecal analgesia.

MATERIALS AND METHODS

Eight mixtures were studied to assess their stability profiles according to the initial drug concentrations used. The solutions obtained were put in implantable pumps and stored at 37 °C over a period of 60 days. Assays were performed using ultra high-pressure liquid chromatography. Turbidity and pH were also measured throughout the study.

RESULTS

Results confirmed excellent physicochemical stability for morphine and ropivacaine. Concerning ziconotide, three of the eight mixtures did not show any sign of chemical instability: average concentrations remained constant throughout the 60 days. A decrease of the concentration was observed for the five other mixtures. Moreover, the appearance of a degradation product linked to oxidation confirmed the ziconotide degradation.

CONCLUSIONS

All these results are in favor of a physicochemical stable preparation for three of the mixture profiles when stored in implantable pumps at 37 °C up to 60 days. For the five others, the efficacy should decrease over time owing to the degradation of ziconotide. The decrease in kinetics of the ziconotide concentration depends on the mixing profile. One possibility is to adapt the filling intervals according to the profile of the mixture. Finally, the results show the period of stability ensuring maximum analgesic efficacy for the eight mixture profiles studied.

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.

Clinical Uses of Intrathecal Therapy and Its Placement in the Pain Care Algorithm

Intrathecal drug delivery is an effective treatment option for patients with severe chronic pain who have not obtained adequate analgesia from more conservative therapies (eg, physical therapy, systemic opioids, nonsteroidal anti-inflammatory drugs, antidepressants, and anticonvulsants). This review focuses on, but is not limited to, the 2 agents currently approved by the U.S. Food and Drug Administration for intrathecal analgesia: preservative-free morphine and ziconotide (a nonopioid, selective N-type calcium channel blocker). We describe the appropriate use of intrathecal therapy in the management of severe chronic pain, based on current best practices. Topics addressed here include patient selection, trialing, dosing and titration, adverse event profiles, long-term management, intrathecal therapy for cancer-related pain, and the placement of intrathecal therapy in the pain care algorithm. In appropriately selected patients with chronic pain, intrathecal therapy can provide substantial pain relief with improved functioning and quality of life. Successful long-term management requires ongoing patient monitoring for changes in efficacy and the occurrence of adverse events, with subsequent changes in intrathecal dosing and titration, the addition of adjuvant intrathecal agents, and the use of concomitant oral medications to address side effects, as needed. Based on an infrequent but clinically concerning risk of overdose, granuloma, and other opioid-induced complications, nonopioid therapy with ziconotide may be preferred as a first-line intrathecal therapy in patients without a history of psychosis or allergy.

Intrathecal drug delivery for pain: a clinical guide and future directions

Intrathecal infusion of medications allows for a direct delivery of agents to the receptors in which they act. This method of treatment is indicated in severe chronic pain of cancer or noncancer origin. In recent years, the use of these devices has increased and the general pain physician, referring doctor and concerned parties such as insurers, needs a better understanding of safety and efficacy. This article is an overview of this therapeutic option and also provides an update on new innovations and forward thinking approaches at improving patient selection and appropriateness of use.

Influence of pH and temperature on ziconotide stability in intrathecal analgesic admixtures in implantable pumps and syringes

PURPOSE

The aim of our study was to investigate the influence of pH and temperature on the stability of ziconotide in analgesic admixtures containing morphine and ropivacaine.

METHODS

All admixtures were combined using a wide range of concentrations, in implantable pumps and syringes, using temperatures from 4°C to 37°C. Quantification was made thanks to a specific chromatographic technique. pH has also been measured throughout the study.

RESULTS

Admixtures confirm excellent stability for morphine and ropivacaine. Concerning ziconotide, an acid hydrolysis has been observed, reducing the time of use of our admixtures in a significant way, but producing non-toxic degradation products. The degradation was linear in all conditions. Inside the implantable pumps at body temperature turned out to be the best conditions for lower protein breakdown. Finally the degradation process showed a high correlation with the pH and the morphine concentration with a median loss of concentration delay due to degradation of 3.5 days [3; 5] when pH<4.5 and 13 days [13; 24] when pH ≥ 4.5.

CONCLUSION

Our admixtures showed different stability depending on the drug concentrations, pH and temperature. The great majority of mixtures in real life in our institution have stability highly compatible with our practice and with the delay between two pump refilling.

Intrathecal drug administration in chronic pain syndromes

Chronic pain may recur after initial response to strong opioids in both patients with cancer and patients without cancer or therapy may be complicated by intolerable side effects. When minimally invasive interventional pain management techniques also fail to provide satisfactory pain relief, continuous intrathecal analgesic administration may be considered. Only 3 products have been officially approved for long-term intrathecal administration: morphine, baclofen, and ziconotide. The efficacy of intrathecal ziconotide for the management of patients with severe chronic refractory noncancer pain was illustrated in 3 placebo-controlled trials. A randomized study showed this treatment option to be effective over a short follow-up period for patients with pain due to cancer or AIDS. The efficacy of intrathecal opioid administration for the management of chronic noncancer pain is mainly derived from prospective and retrospective noncontrolled trials. The effect of intrathecal morphine administration in patients with pain due to cancer was compared with oral or transdermal treatment in a randomized controlled trial, which found better pain control and fewer side effects with intrathecal opioids. Other evidence is derived from cohort studies. Side effects of chronic intrathecal therapy may either be technical (catheter or pump malfunction) or biological (infection). The most troublesome complication is, however, the possibility of granuloma formation at the catheter tip that may induce neurological damage. Given limited studies, the evidence for intrathecal drug administration in patients suffering from cancer-related pain is more compelling than that of chronic noncancer pain.

Ziconotide: a clinical update and pharmacologic review

INTRODUCTION

Ziconotide is an N-type calcium channel antagonist to treat chronic pain that is delivered intrathecally. It is the only intrathecal, FDA-approved, non-opioid analgesic and is recommended as first-line therapy. Despite these advantages, a small therapeutic window limits ziconotide's clinical utility, with adverse event (AE) challenges that include, but are not limited to, dizziness, nausea, and somulence.

AREAS COVERED

Pharmacokinetics, pharmacodynamics, efficacy, safety, trialing, and chronic infusion after searching EMBASE, PubMed, and Cochrane Database of Systemic Reviews were used to search published literature from 1966 to January 1, 2013 to identify studies related to the intrathecal delivery of ziconotide.

EXPERT OPINION

Ziconotide is a safe and effective strategy to treat chronic pain, although limitations remain, including a small therapeutic window. Low starting doses and slow incremental increases and long titration intervals may improve tolerability. AEs may be mitigated by also employing combination therapy, although further study is needed. Concomitant use of ziconotide and morphine is an option when considering use of FDA-labeled intrathecal drugs in those resistant to monotherapy.

Administering ziconotide and monitoring patients treated with ziconotide: expert opinions

Some patients with chronic pain who are intolerant of or refractory to treatment with systemic analgesics may benefit from intrathecal therapy. Ziconotide is the first nonopioid analgesic approved by the United States Food and Drug Administration for intrathecal administration. Several randomized, double-blind, placebo-controlled clinical trials have demonstrated the efficacy and safety of ziconotide. However, the maximum recommended dosing and titration schedule provided in the prescribing information may be too aggressive for some patients, and experience has demonstrated that ziconotide is better tolerated with slower titration to a lower maximum dose. Efficacy can be assessed by an evaluation of changes in pain, functionality, and quality of life. Cognitive adverse events may be subtle; therefore, it is important that health care professionals not only monitor patients for signs and symptoms of cognitive adverse events, but also teach family members how to do the same. Careful patient assessment and monitoring can help optimize the potential benefit from treatment with ziconotide.

Intrathecal therapy: what has changed with the introduction of ziconotide

Administering drugs into the intrathecal space is becoming more popular in the treatment of patients with intractable pain or intolerable side effects of systemic analgesic treatments. Although morphine and ziconotide are the only intrathecal analgesics currently approved by regulatory authorities in the U.S. (Food and Drug Administration) and Europe (national-level approval by individual countries for morphine and European Agency for the Evaluation of Medicinal Products approval for ziconotide), a wide variety of opioid and non-opioid drugs are being used in this way. There is no official guidance concerning the selection of these drugs or their use in combinations and a paucity of efficacy and safety data from randomized controlled trials. The polyanalgesic initiative aims to summarize the current knowledge and to facilitate rational choices of intrathecal drug and drug combinations for the management of chronic pain. The most recent polyanalgesic consensus recommendations were published in 2007. In this review, we shall examine these recommendations, which are tailored toward those practicing intrathecal analgesia in the U.S., and discuss how they should be implemented in Europe, where the healthcare systems and regulations of the medical authorities are different.

Safety and efficacy of intrathecal ziconotide in the management of severe chronic pain

Ziconotide is a conopeptide intrathecal (IT) analgesic which is approved by the US Food and Drug Administration (FDA) for the management of severe chronic pain. It is a synthetic equivalent of a naturally occurring conopeptide found in the venom of the fish-eating marine cone snail and provides analgesia via binding to N-type voltage-sensitive calcium channels in the spinal cord. As ziconotide is a peptide, it is expected to be completely degraded by endopeptidases and exopeptidases (Phase I hydrolytic enzymes) widely located throughout the body, and not by other Phase I biotransformation processes (including the cytochrome P450 system) or by Phase II conjugation reactions. Thus, IT administration, low plasma ziconotide concentrations, and metabolism by ubiquitous peptidases make metabolic interactions of other drugs with ziconotide unlikely. Side effects of ziconotide which tend to occur more commonly at higher doses may include: nausea, vomiting, confusion, postural hypotension, abnormal gait, urinary retention, nystagmus/amblyopia, drowsiness/somnolence (reduced level of consciousness), dizziness or lightheadedness, weakness, visual problems (eg, double vision), elevation of serum creatine kinase, or vestibular side effects. Initially, when ziconotide was first administered to human subjects, titration schedules were overly aggressive and led to an abundance of adverse effects. Subsequently, clinicians have gained appreciation for ziconotide’s relatively narrow therapeutic window. With appropriate usage multiple studies have shown ziconotide to be a safe and effective intrathecal analgesic alone or in combination with other intrathecal analgesics.

Ziconotide: an update and review

BACKGROUND

Ziconotide is the only N-type calcium channel blocker approved by the US FDA for the treatment of chronic pain. The approved indication is for the management of severe chronic pain in patients for whom intrathecal therapy is warranted and who are intolerant of or refractory to other treatments such as systemic analgesics, adjunctive therapies or intrathecal morphine.

OBJECTIVE

The purpose of this article was to review the available safety, efficacy and dosing information for ziconotide.

METHODS

The sources searched for literature from 1980 to January 2008 included Pub Med, MEDLINE and PREMEDLINE using the words ziconotide, conotoxins and pain.

RESULTS/CONCLUSION

Ziconotide is administered intrathecally by infusion pump to block nociceptive signal transmission in the spinal cord. It is a synthetic neuroactive peptide equivalent to the omega conotoxin MVIIA, a constituent of the venom of the fish-hunting marine snail Conus magus. It is highly potent, has a steep dose-response curve, a slow onset of action and a narrow margin of safety and responses to dose adjustments are slow. Patients receiving ziconotide should be under the care of physicians experienced in the management of intrathecal infusion therapy for pain control and should have convenient access to medical facilities.