Current developments in opioid therapy for management of cancer pain

Effects of botulinum toxin A on endometriosis‑associated pain and its related mechanism

Endometriosis (EMS) is a common disease in women aged 25–45 years, and pain is the main clinical symptom. The primary clinical treatment is surgical excision and drug therapy targeting the ectopic lesions, but these have not been very effective. Botulinum neurotoxin serotype A (BTX-A) has been reported to be useful in the treatment of pain in a variety of diseases. Based on this, the aim of the present study was to explore the therapeutic effect and mechanism of BTX-A on EMS. A model of nerve injury induced by oxygen glucose deprivation (OGD) was constructed in PC12 cells and EMS mice. Model cells and mice were treated with different concentrations of BTX-A to observe the changes in pain behavior, to detect cell viability and the secretion of norepinephrine (NE) and methionine enkephalin (M-EK) in cells and the spinal cord, and to evaluate the expression of apoptosis-related molecules in spinal cord nerves. The results revealed that BTX-A significantly reduced the amount of writhing in model mice, enhanced the activity of PC12 OGD cells, increased the secretion of NE and M-EK in model cells and the spinal cord of mice, and decreased the apoptosis of neural cells in the spinal cord of the model mice. Therefore, it was hypothesized that BTX-A may alleviate the pain induced by EMS by increasing the secretion of analgesic substances and promoting the repair of nerve injury. The present study provided a theoretical basis for the treatment of pain induced by EMS.

Lack of Antinociceptive Cross-Tolerance With Co-Administration of Morphine and Fentanyl Into the Periaqueductal Gray of Male Sprague-Dawley Rats

Tolerance to the antinociceptive effect of mu-opioid receptor agonists, such as morphine and fentanyl, greatly limits their effectiveness for long-term use to treat pain. Clinical studies have shown that combination therapy and opioid rotation can be used to enhance opioid-induced antinociception once tolerance has developed. The mechanism and brain regions involved in these processes are unknown. The purpose of this study was to evaluate the contribution of the ventrolateral periaqueductal gray (vlPAG) to antinociceptive tolerance and cross-tolerance between administration and co-administration of morphine and fentanyl. Tolerance was induced by pretreating rats with morphine or fentanyl or low-dose combination of morphine and fentanyl into the vlPAG followed by an assessment of the cross-tolerance to the other opioid. In addition, tolerance to the combined treatment was assessed. Cross-tolerance did not develop between repeated vlPAG microinjections of morphine and fentanyl. Likewise, there was no evidence of cross-tolerance from morphine or fentanyl to the co-administration of morphine and fentanyl. Co-administration did not cause cross-tolerance to fentanyl. Cross-tolerance was only evident to morphine or morphine and fentanyl combined in rats pretreated with co-administration of low doses of morphine and fentanyl. This finding is consistent with the functionally selective signaling that has been reported for antinociception and tolerance after morphine and fentanyl binding to the mu-opioid receptor. This research supports the notion that combination therapy and opioid rotation may be useful clinical practices to decrease opioid tolerance and other side effects. PERSPECTIVE: This preclinical study shows that there is a decrease in cross-tolerance between morphine and fentanyl within the periaqueductal gray, which is a key brain region in opioid antinociception and tolerance.

Practical management of opioid rotation and equianalgesia

Purpose

To review the recent literature on opioid rotation (ie, switching from one opioid drug to another or changing an opioid’s administration route) in cancer patients experiencing severe pain and to develop a novel equianalgesia table for use in routine clinical practice.

Methods

The MEDLINE database was searched with terms “cancer pain,” “opioid rotation,” “opioid switching,” “opioid ratio,” “opioid conversion ratio,” and “opioid equianalgesia” for the major opioids (morphine, oxycodone, fentanyl, and hydromorphone) and the intravenous, subcutaneous, oral, and transdermal administration routes. Selected articles were assessed for the calculated or cited opioid dose ratio, bidirectionality, and use of the oral morphine equivalent daily dose or a direct drug-to-drug ratio.

Results

Twenty publications met our selection criteria and were analyzed in detail. We did not find any large-scale, prospective, double-blind randomized controlled trial with robust design, and most of the studies assessed relatively small numbers of patients. Bidirectionality was investigated in seven studies only.

Conclusion

The updated equianalgesic table presented here incorporates the latest data and provides information on bidirectionality. Despite the daily use of equianalgesic tables, they are not based on high-level scientific evidence. More clinical research is needed on this topic.

Dental Management of Patients Who Have Undergone Oral Cancer Therapy

Oral cancer therapies are associated with orofacial complications that could result in dose-limiting cancer treatment and consequent suboptimal tumor control. Oral cancer treatment complications include oral mucositis, salivary gland hypofunction, odontogenic infections, pain, dermatitis, neurotoxicity, soft tissue fibrosis, trismus, osteoradionecrosis, and potential cancer recurrence. These complications significantly affect cancer survivorship, quality of life, and psychosocial status. Effective dental management of patients with oral cancer involves the coordination of care among several health care professionals before, during, and after cancer therapy. The goal is to minimize complications, and establish optimal quality of life for survivors.

Efficacy and Safety of Ropivacaine Addition to Intrathecal Morphine for Pain Management in Intractable Cancer

Objective. Although intrathecal drug infusion has been commonly adopted for terminal cancer pain relief, its adverse effects have made many clinicians reluctant to employ it for intractable cancer pain. The objective of this study is to compare the efficacy and security of an intrathecal continuous infusion of morphine and ropivacaine versus intrathecal morphine alone for cancer pain. Methods. Thirty-six cancer patients received either a continuous morphine (n = 19) or morphine and ropivacaine (n = 17) infusion using an intrathecal catheter through a subcutaneous port. Numerical Rating Scale (NRS) scores and the Barthel Index were analyzed. Adverse effects and complications on postoperative days 1, 3, 7, and 15 were also analyzed. Results. All patients experienced pain relief. Compared to those who received morphine alone, patients receiving morphine and ropivacaine had significantly lower postoperative morphine requirements and higher Barthel Index scores on the 15th postsurgical day (P < 0.05). Patients receiving morphine and ropivacaine had lower NRS scores than patients receiving morphine alone on postoperative days 1, 3, 7, and 15 (P < 0.05). Negative postsurgical effects were similar in both groups. Conclusions. Morphine and ropivacaine administration through intrathecal access ports is efficacious and safe and significantly improves quality of life.

Morphine or oxycodone for cancer-related pain? A randomized, open-label, controlled trial

CONTEXT

There is wide interindividual variation in response to morphine for cancer-related pain; 30% of patients do not have a good therapeutic outcome. Alternative opioids such as oxycodone are increasingly being used, and opioid switching has become common clinical practice.

OBJECTIVES

To compare clinical response to oral morphine vs. oral oxycodone when used as first-line or second-line (after switching) treatment in patients with cancer-related pain.

METHODS

In this prospective, open-label, randomized, controlled trial (ISRCTN65155201) with a selected crossover phase, patients with cancer-related pain were randomized to receive either oral morphine or oxycodone as first-line treatment. Dose was individually titrated until the patient reported adequate pain control. Patients who did not respond to the first-line opioid (either because of inadequate analgesia or unacceptable adverse effects) were switched to the alternative opioid.

RESULTS

Two hundred patients were recruited. On intention-to-treat analysis (n = 198, morphine 98, oxycodone 100), there was no significant difference between the numbers of patients responding to morphine (61/98 = 62%) or oxycodone (67/100 = 67%) when used as a first-line opioid. Similarly, there was no significant difference in subsequent response when patients were switched to either morphine (8/12 = 67%) or oxycodone (11/21 = 52%). Per-protocol analysis demonstrated a 95% response rate when both opioids were available. There was no difference in adverse reaction scores between morphine and oxycodone either in first-line responders or nonresponders.

CONCLUSION

In this population, there was no difference between analgesic response or adverse reactions to oral morphine and oxycodone when used as a first- or second-line opioid. These data provide evidence to support opioid switching to improve outcomes.

[Dependency syndrome and hyperalgesia due to an opioid therapy for curative treatable pain. Case report of an apparent palliative patient]

Opioids are an essential part of cancer pain management but particularly in this patient group physicians could misinterpret opioid-induced potentially life-threatening side effects within the central nervous system (CNS) or hyperalgesia as a consequence of tumor progression. In this case increasing the opioid dose or switching to rapidly acting opioids may trigger a vicious circle. We describe a case report of a male patient who was treated with high doses of transdermal and endonasal fentanyl 2 years after pancreatomy due to cancer. The patient was referred to the palliative care unit presenting with delirious behavior and 30-40 severe abdominal pain attacks/day. After withdrawal of the opioid medication all CNS symptoms disappeared. Further diagnostics revealed multiple incisional hernia as the reason of the pain syndrome. The patient recovered after herniotomy and has now been pain free without any pain medication for more than 16 months. This case report underlines again the necessity of pain diagnostics also in assumed palliative patients with the risks of high dose opioid treatment.

Platelet-rich plasma and the elimination of neuropathic pain

Peripheral neuropathic pain typically results from trauma-induced nociceptive neuron hyperexcitability and their spontaneous ectopic activity. This pain persists until the trauma-induced cascade of events runs its full course, which results in complete tissue repair, including the nociceptive neurons recovering their normal biophysical properties, ceasing to be hyperexcitable, and stopping having spontaneous electrical activity. However, if a wound undergoes no, insufficient, or too much inflammation, or if a wound becomes stuck in an inflammatory state, chronic neuropathic pain persists. Although various drugs and techniques provide temporary relief from chronic neuropathic pain, many have serious side effects, are not effective, none promotes the completion of the wound healing process, and none provides permanent pain relief. This paper examines the hypothesis that chronic neuropathic pain can be permanently eliminated by applying platelet-rich plasma to the site at which the pain originates, thereby triggering the complete cascade of events involved in normal wound repair. Many published papers claim that the clinical application of platelet-rich plasma to painful sites, such as muscle injuries and joints, or to the ends of nerves evoking chronic neuropathic pain, a process often referred to as prolotherapy, eliminates pain initiated at such sites. However, there is no published explanation of a possible mechanism/s by which platelet-rich plasma may accomplish this effect. This paper discusses the normal physiological cascade of trauma-induced events that lead to chronic neuropathic pain and its eventual elimination, techniques being studied to reduce or eliminate neuropathic pain, and how the application of platelet-rich plasma may lead to the permanent elimination of neuropathic pain. It concludes that platelet-rich plasma eliminates neuropathic pain primarily by platelet- and stem cell-released factors initiating the complex cascade of wound healing events, starting with the induction of enhanced inflammation and its complete resolution, followed by all the subsequent steps of tissue remodeling, wound repair and axon regeneration that result in the elimination of neuropathic pain, and also by some of these same factors acting directly on neurons to promote axon regeneration thereby eliminating neuropathic pain.

Trends in the consumption of opioid analgesics in Taiwan from 2002 to 2007: a population-based study

CONTEXT

Morphine consumption is an important indicator of a country's progress in cancer pain relief. However, opioid prescription data are lacking for Taiwan.

OBJECTIVES

To investigate opioid consumption patterns in Taiwan, compare the results with those from selected countries, identify differences between patients with and without cancer, and determine the associated expenditure.

METHODS

Data on prescriptions for three so-called strong opioids (fentanyl, morphine, and pethidine [meperidine]) and one so-called weak opioid (codeine) were obtained from the Taiwan National Health Insurance Research Database for 2002-2007. The data were converted into a defined daily dose for statistical purposes per million inhabitants per day. Associated payments and diagnoses also were obtained from the database.

RESULTS

From 2002 to 2007, opioid consumption in Taiwan increased by 55% from 362 to 560 defined daily dose for statistical purposes per million inhabitants per day. This ranks Taiwan as 56th among 181 countries and areas according to the statistical data for 2005-2007 from the International Narcotics Control Board. Among the investigated opioids, prescriptions for transdermal fentanyl and oral morphine increased markedly from 2002 to 2007. Pethidine (meperidine) was predominantly prescribed to patients without cancer diagnoses (around 80%). The total expenditure on opioid prescriptions was US$10.2 million in 2007 for a population of 23 million.

CONCLUSION

Opioid prescriptions and expenditure increased steadily from 2002 to 2007 in Taiwan, as in nearby Asian countries, but remained much lower than in developed countries. Pethidine (meperidine) was predominantly prescribed to noncancer patients, whereas morphine and fentanyl were mainly prescribed for cancer patients.

Neuropathic pain: a personal case reflection on a critical incident

Neuropathic pain is a distressing symptom for the patient and a difficult symptom for the physician to treat. There is lack of evidence-based clinical guidelines for the management of malignant neuropathic pain. The case reflection is a personal account of what has been learnt from a critical incident in a particular patient in the management of neuropathic pain. Psychological issues are known to increase pain percetion and affect the quality of life. The case reflection explores problem areas, defines lacunae in knowledge, and demonstrates active learning of the management of neuropathic pain through reflective practice.

Cancer pain management-current status

Cancer pain is still one of the most feared entities in cancer and about 75% of these patients require treatment with opioids for severe pain.The cancer pain relief is difficult to manage in patients with episodic or incidental pain, neuropathic pain, substance abuse and with impaired cognitive or communication skills. This non-systematic review article aims to discuss reasons for under treatment, tools of pain assessment, cancer pain and anxiety and possibly carve new approaches for cancer pain management in future. The current status of World Health Organization analgesic ladder has also been reviewed. A thorough literature search was carried out from 1998 to 2010 for current status in cancer pain management in MEDLINE, WHO guidelines and published literature and relevant articles have been included.

The use of opioids at the end of life: the knowledge level of Dutch physicians as a potential barrier to effective pain management

BACKGROUND

Pain is still one of the most frequently occurring symptoms at the end of life, although it can be treated satisfactorily in most cases if the physician has adequate knowledge. In the Netherlands, almost 60% of the patients with non-acute illnesses die at home where end of life care is coordinated by the general practitioner (GP); about 30% die in hospitals (cared for by clinical specialists), and about 10% in nursing homes (cared for by elderly care physicians).The research question of this study is: what is the level of knowledge of Dutch physicians concerning pain management and the use of opioids at the end of life?

METHODS

A written questionnaire was sent to a random sample of physicians of specialties most often involved in end of life care in the Netherlands. The questionnaire was completed by 406 physicians, response rate 41%.

RESULTS

Almost all physicians were aware of the most basal knowledge about opioids, e.g. that it is important for treatment purposes to distinguish nociceptive from neuropathic pain (97%). Approximately half of the physicians (46%) did not know that decreased renal function raises plasma concentration of morphine(-metabolites) and 34% of the clinical specialists erroneously thought opioids are the favoured drug for palliative sedation.Although 91% knew that opioids titrated against pain do not shorten life, 10% sometimes or often gave higher dosages than needed with the explicit aim to hasten death. About half felt sometimes or often pressured by relatives to hasten death by increasing opioiddosage.The large majority (83%) of physicians was interested in additional education about subjects related to the end of life, the most popular subject was opioid rotation (46%).

CONCLUSIONS

Although the basic knowledge of physicians was adequate, there seemed to be a lack of knowledge in several areas, which can be a barrier for good pain management at the end of life. From this study four areas emerge, in which it seems likely that an improvement can improve the quality of pain management at the end of life for many patients in the Netherlands: 1)palliative sedation; 2)expected effect of opioids on survival; and 3) opioid rotation.

Effects of chronic fentanyl administration on physical performance of aged rats

There is growing concern over the increasing use of opioids to treat chronic pain in the elderly primarily because of the potential increased sensitivity to the adverse side effects. Here, we use a preclinical model (male Brown Norway X F344 rats aged 12, 18, 24, and 30 months) to describe the outcome of chronic fentanyl administration (1.0mg/kg/day) on various physiological and behavioral measures. Continuous fentanyl administration resulted in an initial decrease in food consumption, followed by the development of tolerance to this effect over a 4-week period and a subsequent increase in food consumption during withdrawal. This change in food consumption was associated with decreases in body weight (predominantly due to a loss of fat mass) that was maintained through early withdrawal. After 1 month of withdrawal, only the 12-month old animals had fully regained body weight. Fentanyl administration resulted in a decrease in grip strength and an increase in locomotor activity that did not differ across age groups. There was no effect of fentanyl administration on rotarod performance. These results demonstrate that while there is a delayed recovery of body mass with age, the observed changes in behavioral responses are uniform across ages.

Palliative care for the cancer patient

Palliation of symptoms to optimize QOL is the foundation of cancer care regardless of stage of disease or level of anticancer treatment. Patients commonly experience pain, constipation, nausea, vomiting, dyspnea, fatigue, and delirium. Many valid clinical tools are available to the primary care clinician to screen for symptoms, assess severity, measure treatment response, and elicit the patient's subjective symptom experience. Although there is limited evidence regarding the relative efficacy of symptom interventions from randomized controlled trials, clinical practice guidelines are available.

A randomized, double-blind comparison of OROS(R) hydromorphone and controlled-release morphine for the control of chronic cancer pain

BACKGROUND

Long-acting opioid formulations are advocated for maintaining pain control in chronic cancer pain. OROS(R) hydromorphone is a sustained-release formulation of hydromorphone that requires dosing once daily to maintain therapeutic concentrations. The objective of this study was to demonstrate the clinical equivalence of immediate-release and sustained-release formulations of hydromorphone and morphine for chronic cancer pain.

METHODS

200 patients with cancer pain (requiring </= 540 mg/d of oral morphine) participated in this double-blind, parallel-group trial. Patients were randomized to receive hydromorphone or morphine (immediate-release for 2-9 days, sustained-release for 10-15 days). Efficacy was assessed with the Brief Pain Inventory (BPI), investigator and patient global evaluations, Eastern Cooperative Oncology Group performance status, and the Mini-Mental State Examination. The primary endpoint was the 'worst pain in the past 24 hours' item of the BPI, in both the immediate-release and sustained-release study phases, with treatments deemed equivalent if the 95% confidence intervals (CI) of the between-group differences at endpoint were between -1.5 and 1.5. No equivalence limits were defined for secondary endpoints.

RESULTS

Least-squares mean differences (95% CI) between groups were 0.2 (-0.4, 0.9) in the immediate-release phase and -0.8 (-1.6, -0.01) in the sustained-release phase (intent-to-treat population), indicating that the immediate-release formulations met the pre-specified equivalence criteria, but that the lower limit of the 95% CI (-1.6) was outside the boundary (-1.5) for the sustained-release formulations. BPI 'pain now PM' was significantly lower with OROS(R) hydromorphone compared with controlled-release morphine (least-squares mean difference [95% CI], -0.77 [-1.49, -0.05]; p = 0.0372). Scores for other secondary efficacy variables were similar between the two sustained-release treatments. At endpoint, > 70% of investigators and patients rated both treatments as good to excellent. The safety profiles of hydromorphone and morphine were similar and typical of opioid analgesics.

CONCLUSION

Equivalence was demonstrated for immediate-release formulations of hydromorphone and morphine, but not for the sustained-release formulations of OROS(R) hydromorphone and controlled-release morphine. The direction of the mean difference between the treatments (-0.8) and the out-of-range lower limit of the 95% CI (-1.6) were in favor of OROS(R) hydromorphone.

TRIAL REGISTRATION

ClinicalTrials.gov: NCT0041054.