Karen H. Simpson

Fixed-ratio combination oxycodone/naloxone compared with oxycodone alone for the relief of opioid-induced constipation in moderate-to-severe noncancer pain

ABSTRACT Objective: Opioid therapy is frequently associated with treatment-limiting constipation. Naloxone is an opioid antagonist with low oral systemic bioavailability. This Phase III clinical trial assessed the safety and efficacy of an oral fixed-ratio combination of oxycodone prolonged-release (PR) and naloxone PR compared with oxycodone PR in relieving opioid-induced constipation. Study design: This double-blind, multicenter trial was conducted in specialist and primary care centers in four European countries in an out-patients setting. The study included 322 adult patients with moderate-to-severe, noncancer pain requiring opioid therapy in a range of ≥20 mg/day and ≤50 mg/day oxycodone. Following a run-in phase patients were randomized to receive oxycodone PR/naloxone PR or oxycodone PR for 12 weeks. The primary outcome was improvement in constipation as measured using the Bowel Function Index (BFI). Secondary/exploratory assessments focused on pain intensity and additional bowel parameters. Trial registration: NCT00412152. Results: A significant improvement in BFI scores occurred with oxycodone PR/naloxone PR compared with oxycodone PR after 4 weeks of double-blind treatment (−26.9 vs. −9.4, respectively; p < 0.0001), observed after only 1 week of treatment and continued until study end. A significant increase in the number of complete spontaneous bowel movements and decrease in laxative use were also reported. This improvement in bowel function was achieved without compromising the analgesic efficacy of the oxycodone component; pain intensity remained constant throughout the study. The incidence of adverse events was comparable in both groups and consistent with those expected of opioid analgesics. As the study was limited to a dose range of up to 50 mg oxycodone equivalent per day, further research on higher doses would be recommended. Conclusion: The fixed-ratio combination of oxycodone PR/naloxone PR is superior to oxycodone PR alone, offering patients effective analgesia while significantly improving opioid-induced constipation.

Gabapentin in the treatment of neuropathic pain.

This paper reviews the pharmacology and clinical effectiveness of gabapentin in the treatment of neuropathic pain. Gabapentin has antihyperalgesic and antiallodynic properties but does not have significant actions as an anti-nociceptive agent. Its mechanisms of action appear to be a complex synergy between increased GABA synthesis, non-NMDA receptor antagonism and binding to the α2δ subunit of voltage dependent calcium channels. The latter action inhibits the release of excitatory neurotransmitters. Clinically, several large randomized controlled trials have demonstrated its effectiveness in the treatment of a variety of neuropathic pain syndromes. Patients with neuropathic pain can expect a mean reduction in pain score of 2.05 points on an 11 point numerical rating scale compared with a reduction of 0.94 points if they had taken the placebo. Around 30% of patients can expect to achieve more than 50% pain relief and a similar number will also experience minor adverse events; the most common of which are somnolence and dizziness. In patients with neuropathic pain due to cancer, higher response rates might be observed with gabapentin when administered with opioids because of a synergistic interaction.

Efficacy and safety of transdermal fentanyl and sustained-release oral morphine in patients with cancer and chronic non-cancer pain.

SUMMARY Purpose: To evaluate effectiveness and safety information of transdermal fentanyl (TDF) (Duragesic/Durogesic*) and sustained-release oral morphine (SRM) in cancer pain (CP) and chronic non-cancer pain (NCP), a pooled analysis was conducted on datasets of published, open label, uncontrolled (no comparator group) and randomised controlled (with SRM as comparator) studies of TDF. Patients and methods: Eight trials with treatment durations of at least 28 days met the inclusion criteria. The effectiveness analysis assessed changes in average pain and pain ‘right now’ scores between baseline and Day 28. The safety analysis evaluated the incidence of adverse events (AEs) reported within the first 28 days of treatment with TDF or SRM. Subgroup analyses included pain type, gender, age, weight, and body mass index. Results: Pooled efficacy data were available from 1220 patients; these showed that both TDF and SRM were effective in improving pain ‘right now’ scores (0–100 scale) from baseline to Day 28. The improvement was significantly more pronounced in the TDF treatment group (–26.7 ± 31.3 for TDF, –18.7 ± 30.9 for SRM, p = 0.002). This favourable effect of TDF was most apparent amongst patients with NCP. Data concerning AEs were available from over 2500 patients with CP (3 out of 10 patients) or chronic NCP (7 out of 10 patients). Significantly fewer patients in the TDF than in the SRM group reported any AE (72% vs. 87% respectively; p < 0.001), or an AE leading to the study drug being permanently discontinued (16% vs. 23% respectively; p < 0.001). Constipation and somnolence occurred considerably less frequently in the TDF than in the SRM treatment group. This difference was statistically significant in both the CP and NCP subgroups. Conclusion: This pooled data analysis provides expanded insight into the safety and effectiveness profile of transdermal fentanyl in patients with chronic pain. It shows significantly improved pain relief with transdermal fentanyl compared with sustained-release oral morphine, and supports current evidence of favourable tolerability of transdermal fentanyl, particularly with regard to reduced constipation and somnolence.

Efficacy and safety of combined prolonged-release oxycodone and naloxone in the management of moderate/severe chronic non-malignant pain: results of a prospectively designed pooled analysis of two randomised, double-blind clinical trials

BackgroundTwo randomised 12-week, double-blind, parallel-group, multicenter studies comparing oxycodone PR/naloxone PR and oxycodone PR alone on symptoms of opioid-induced bowel dysfunction in patients with moderate/severe non-malignant pain have been conducted.MethodsThese studies were prospectively designed to be pooled and the primary outcome measure of the pooled data analysis was to demonstrate non-inferiority in 12-week analgesic efficacy of oxycodone PR/naloxone PR versus oxycodone PR alone. Patients with opioid-induced constipation were switched to oxycodone PR and then randomised to fixed doses of oxycodone PR/naloxone PR (n = 292) or oxycodone PR (n = 295) for 12 weeks (20-80 mg/day).ResultsNo statistically significant differences in analgesic efficacy were observed for the two treatments (p = 0.3197; non-inferiority p < 0.0001; 95% CI -0.07, 0.23) and there was no statistically significant difference in frequency of analgesic rescue medication use. Improvements in Bowel Function Index score were observed for oxycodone PR/naloxone PR by Week 1 and at every subsequent time point (-15.1; p < 0.0001; 95% CI -17.3, -13.0). AE incidence was similar for both groups (61.0% and 57.3% of patients with oxycodone PR/naloxone PR and oxycodone PR alone, respectively).ConclusionsResults of this pooled analysis confirm that oxycodone PR/naloxone PR provides effective analgesia and suggest that oxycodone PR/naloxone PR improves bowel function without compromising analgesic efficacy.Trial registration numbersClinicalTrials.gov identifier: NCT00412100 and NCT00412152

Can chronic neuropathic pain following thoracic surgery be predicted during the postoperative period

Chronic pain following thoracic surgery is common and associated with neuropathic symptoms, however, the proportion of patients with neuropathic pain in the immediate postoperative period is unknown. We aimed to determine the proportion of patients who have neuropathic symptoms and signs immediately after, and at three months following thoracic surgery. The study was designed as a prospective observational cohort study. We identified patients with pain of predominantly neuropathic origin using the Leeds Assessment of Neuropathic Symptoms and Signs (LANSS) score in the immediate postoperative period and the self-report LANSS (S-LANSS) version three months after surgery. One hundred patients undergoing video assisted thoracic surgery (VATS) or thoracotomy completed LANSS scores preoperatively and in the immediate postoperative period. Eighty-seven percent completed three months S-LANSS follow-up scores. Eight percent of patients had positive LANSS scores in the immediate postoperative period; 22% of patients had positive S-LANSS scores three months following surgery. There was a significant association between positive scores in the acute and chronic periods (relative risk (RR) 3.5, [95% confidence interval (CI) 1.7-7.2]). Identifying pain of predominantly neuropathic origin in the postoperative period with a simple pain score can help identify those at risk of developing chronic pain with these features following thoracic surgery.

Clinical Pharmacokinetics of Ondansetron. A Review

5−HT3 receptors are ubiquitous in the enteric, sympathetic, parasympathetic and sensory nervous systems and in the central nervous system (CNS) (Kilpatrick et al 1990). In man 5−HT3 receptors are mainly situated on enterochromaffin cells in the gastrointestinal mucosa, which are innervated by vagal afferents (Reynolds et al 1989), and the area postrema of the brain stem, which forms the chemoreceptor trigger zone. Ondansetron is a selective antagonist at 5−HT3 receptors. It is 100 times more potent than metoclopramide at this site (Tyers 1992). It shows limited binding to other receptors and has a wide therapeutic window. Ondansetron is a useful antiemetic which probably has both central and peripheral actions in patients undergoing radiotherapy, cytotoxic chemotherapy or general anaesthesia (Naylor & Rudd 1992). This paper reviews the pharmacokinetics of ondansetron in health and disease to provide information for clinicians; it might alter prescribing and alert them to possible drug interactions.

A Cochrane Systematic Review of Transcutaneous Electrical Nerve Stimulation for Cancer Pain

Cancer-related pain is complex and multi-dimensional; yet, the mainstay of cancer pain management has been the biomedical approach. There is a need for nonpharmacological and innovative pain management strategies. Transcutaneous electrical nerve stimulation (TENS) may have a role. The aim of this systematic review was to determine the effectiveness of TENS for cancer-related pain in adults. The Cochrane Library, MEDLINE, EMBASE, CINAHL, PsychINFO, AMED, and PEDro databases were searched for randomized controlled trials (RCTs) investigating the use of TENS for the management of cancer-related pain in adults. Once relevant studies were identified, two pairs of reviewers assessed eligibility for inclusion in the review based on a study eligibility form and using the 5-point Oxford Quality Scale. Two RCTs met the study eligibility criteria (these involved 64 patients). These studies were heterogeneous with respect to study population, methodology, and outcome measures. This prevented meta-analysis. In one RCT, there were no significant differences between TENS and placebo in women with chronic pain secondary to breast cancer treatment. In the other RCT, there were no significant differences between acupuncture-like TENS (AL-TENS) and sham in palliative care patients; this study was significantly underpowered. There is insufficient available evidence to determine the effectiveness of TENS in treating cancer-related pain. Further research is needed to help guide clinical practice, and large multi-center RCTs are required to assess the value of TENS in the management of cancer-related pain in adults.

Bolus Intrathecal Injection of Ziconotide (Prialt®) to Evaluate the Option of Continuous Administration via an Implanted Intrathecal Drug Delivery (ITDD) System: A Pilot Study

This study evaluated efficacy and safety of bolus doses of ziconotide (Prialt®, Eisai Limited, Hertfordshire, UK) to assess the option of continuous administration of this drug via an implanted intrathecal drug delivery system.

Fixed ratio (2:1) prolonged-release oxycodone/naloxone combination improves bowel function in patients with moderate-to-severe pain and opioid-induced constipation refractory to at least two classes of laxatives

Abstract Objective: The effects of combined oxycodone/naloxone prolonged release tablets (OXN PR) were investigated in patients with moderate-to-severe chronic cancer-related or non-cancer pain. All patients had opioid-induced constipation (OIC) which persisted despite substantial laxative therapy. Research design and methods: This pooled analysis included 75 patients with OIC at study entry that was refractory to at least two laxatives with different modes of action. Patients completed randomized, double-blind treatment with OXN PR 20–120 mg/day for either 12 weeks (OXN 9001: non-cancer pain study) or 4 weeks (OXN 2001: cancer-related pain study). Analgesia and bowel function were assessed using the Brief Pain Inventory Short Form and Bowel Function Index (BFI), respectively. Use of laxative medication and safety were assessed throughout the studies. Clinical trial registration: ClinicalTrials.gov identifier: NCT00513656. EudraCT 2005-002398-57, EudraCT 2005-003510-15. Results: Statistically and clinically significant improvements in bowel function were observed following double-blind treatment with OXN PR. Mean (SD) reduction in BFI score was 21.2 (28.8) and comparable in patients with cancer-related (19.0 [28.9]) and non-cancer pain (23.3.[29.0]; P ≤ 0.0002). Furthermore, the proportion of patients with a BFI score within normal range (≤28.8) increased from 9.5% at screening to 43.1% at Day 15 of OXN PR. While all patients used ≥2 laxatives of different classes at screening, during study treatment 36% stopped using laxatives (P < 0.001). OXN PR provided effective analgesia, evidenced by stable pain scores during study treatment, and there were no unanticipated adverse events. Conclusions: OXN PR significantly improved bowel function and reduced the use of laxatives in patients with OIC, previously unresponsive to at least two different classes of laxatives. OXN also provided effective analgesia for patients with moderate-to-severe cancer-related pain and non-cancer-related pain.

New Formulation of Sustained Release Naloxone Can Reverse Opioid Induced Constipation Without Compromising the Desired Opioid Effects

UNLABELLED An international double-blind randomized placebo controlled study evaluated the safety and efficacy of four doses of a new sustained release naloxone capsule to treat Opioid Induced Constipation (OIC). METHODS Forty patients taking opioids for noncancer related pain, and experiencing OIC, were randomized into 4 cohorts of 10 patients. A multiple ascending dose design was used to evaluate the safety and efficacy of 2.5 mg, 5 mg, 10 mg, and 20 mg naloxone sustained release (NSR) capsules vs placebo. Drug was given once-daily for 3 weeks followed by twice daily (bid) dosing between weeks 4 and 6. RESULTS The incidence of treatment emergent adverse events was highest in the placebo group. The incidence of adverse events among the four active treatment groups were similar. There were no serious adverse events. The number of severe events was low overall but highest in the placebo group. Significant improvements were seen in Spontaneous Bowel Movements with 5 mg, 10 mg, and 20 mg NSR capsules. Mean change in SBMs from baseline of 2.21 (P = 0.052), 2.37 (P = 0.032); 4.11 (P = 0.0005); 5.19 (<0.0001) was noted with NSR 2.5 mg, 5 mg, 10 mg, and 20 mg, respectively, when taken once daily, compared with 1.38 (P = 0.2) for patients on placebo therapy. No changes in subjective or objective measures of opioid withdrawal as measured by the Subjective Opioid Withdrawal Scale or Clinical Opioid Withdrawal Scale were observed. There was no increase in patient reported pain as measured daily using a visual analogue scale. CONCLUSIONS This Phase II study has shown that using a new sustained release formulation to deliver oral naloxone to the colon allows successful treatment of OIC without comprising the desired opioid effects.