Opioid-induced hyperalgesia: fact or fiction?

Opioid-induced Neurotoxicity in Patients with Cancer Pain

OPINION STATEMENT

Opioid-induced neurotoxicity (OINT) is a neuropsychiatric syndrome observed with opioid therapy. The mechanism of OINT is thought to be multifactorial, and many risk factors may facilitate its development. If symptoms of OINT are seen, the prescriber should consider hydration, discontinuation of the offending opioid drug, or switching of opioid medication, or the use of some adjuvants. Multiple factors like inter- and intraindividual differences in opioid pharmacology may influence the accuracy of dose calculations for opioid switching. Experience and clinical judgment in a specialistic palliative care setting should be used and individual patient characteristics considered when applying any conversion table.

A Case of Opioid-Induced Hyperalgesia

We report the case of a 76 year old lady with metastatic breast cancer, who presented to a hospice in severe distress from uncontrolled pain despite an increase in her opioid dose, alongside generalised hypersensitivity and delirium. The clinical presentation suggested opioid-induced hyperalgesia (OIH). After reduction of the opioid dose, our patient significantly improved to the extent she was discharged home a few weeks later. This report aims to increase awareness of OIH, a clinical phenomenon which remains poorly understood and probably under recognised.

Targeting Opioid-Induced Hyperalgesia in Clinical Treatment: Neurobiological Considerations

Opioid analgesics have become a cornerstone in the treatment of moderate to severe pain, resulting in a steady rise of opioid prescriptions. Subsequently, there has been a striking increase in the number of opioid-dependent individuals, opioid-related overdoses, and fatalities. Clinical use of opioids is further complicated by an increasingly deleterious profile of side effects beyond addiction, including tolerance and opioid-induced hyperalgesia (OIH), where OIH is defined as an increased sensitivity to already painful stimuli. This paradoxical state of increased nociception results from acute and long-term exposure to opioids, and appears to develop in a substantial subset of patients using opioids. Recently, there has been considerable interest in developing an efficacious treatment regimen for acute and chronic pain. However, there are currently no well-established treatments for OIH. Several substrates have emerged as potential modulators of OIH, including the N-methyl-D-aspartate and γ-aminobutyric acid receptors, and most notably, the innate neuroimmune system. This review summarizes the neurobiology of OIH in the context of clinical treatment; specifically, we review evidence for several pathways that show promise for the treatment of pain going forward, as prospective adjuvants to opioid analgesics. Overall, we suggest that this paradoxical state be considered an additional target of clinical treatment for chronic pain.

A systematic review of combination step III opioid therapy in cancer pain: an EPCRC opioid guideline project

BACKGROUND

The use of combinations of opioids is a common clinical practice; however, this is not advocated by the World Health Organization (WHO) analgesic ladder. As opioid combination therapy becomes used increasingly, a review of the evidence on this practice was conducted.

AIMS

To carry out a systematic review of the use of strong opioids in combination in cancer pain.

METHODS

The following databases were searched electronically: Embase (1980-2010 week 2), Medline (1950-2010 week 1) and the Cochrane Database of Systematic Reviews (fourth quarter 2009). Only strong opioids as defined by the WHO ladder and full opioid agonists were examined. Only studies conducted in human, adult patients with chronic cancer pain were eligible. Studies must have contained data on efficacy and/or side effects in the key point. Appraisal was conducted using predetermined criteria set by the EAPC guideline development group. All potential papers were reviewed independently by both authors.

RESULTS

In total 596 articles were retrieved resulting in only two eligible studies, which were rated as grade C and grade D evidence. These examined morphine in combination with oxycodone or fentanyl/methadone.

CONCLUSION

Only a weak recommendation can be used to support combination opioid therapy. This recommendation is also based on the caveat that the desirable effects of combination opioid therapy is outweighed by any disadvantages that this would confer. Prospective randomized trials are needed to clarify the benefits and safety of combination opioid therapy.

Inappropriate use of high doses of transdermal fentanyl at admission to a palliative care unit

A retrospective study was conducted to determine the patterns of strong opioid use in patients admitted to a hospice inpatient unit, with special attention to the use of the transdermal fentanyl patch. This study was conducted to validate or negate the subjective feeling that many patients, treated at admittance with the fentanyl patch, received inappropriately high doses compared to patients treated with oral or parenteral opioids. The case notes of 1154 patients were reviewed and data collected on age, sex, diagnosis, care settings, opioid form and dose on referral, maximal dose during admission and opioid use during the last 24 hours of their life. At admission opioids had been prescribed for 47% of patients. Thirty-two percent of these patients received oral morphine. The median dose at admission of those patients was 60 mg (oral morphine equivalent (OME)). Thirty-six percent of the patients on opioids were using the fentanyl patch. The median dose at admission was triple that of the orally treated patients (median 180 mg OME). In the 199 patients using transdermal fentanyl at admission, in most patients the dose of the patch was gradually diminished and finally stopped in 58% of patients. Only 83 kept it until the last 24 hours. We would like to draw attention to the fact that (sometimes inappropriately) high doses of fentanyl were used at admission, probably due to lack of knowledge of the relative strength of the opioid involved and to the failure to recognize the phenomenon of opioid-induced hyperalgesia. In addition, in our experience the long action of the patch can be a disadvantage during the last days and weeks of life, due to the difficulty of dose adjustment and the risk for toxicity.

Routines and rituals: a grounded theory of the pain management of drug users in acute care settings

AIM

This study reviewed the perceptions and strategies of drug users and nurses with regard to pain management in acute care settings.

BACKGROUND

Drug users present unique challenges in acute care settings with pain management noted to be at best suboptimal, at worst non-existent. Little is known about why and specifically how therapeutic effectiveness is compromised.

DESIGN

Qualitative: constructivist grounded theory.

METHOD

A constructivist grounded theory approach incorporating a constant comparative method of data collection and analysis was applied. The data corpus comprised interviews with drug users (n = 11) and five focus groups (n = 22) of nurses and recovering drug users.

RESULTS

Moral relativism as the core category both represents the phenomenon and explains the basic social process. Nurses and drug users struggle with moral relativism when addressing the issue of pain management in the acute care setting. Drug users lay claim to expectations of compassionate care and moralise via narration. Paradoxically, nurses report that the caring ideal and mutuality of caring are diminished. Drug users' individual sensitivities, anxieties and felt stigma in conjunction with opioid-induced hyperalgesia complicate the processes. Nurses' and hospitals' organisational routines challenge drug user rituals and vice versa leading both protagonists to become disaffected. Consequently, key clinical issues such as preventing withdrawal and managing pain are left unaddressed and therapeutic effectiveness is compromised.

CONCLUSION

This study provides a robust account of nurses' and drug users' struggle with pain management in the acute care setting. Quick technological fixes such as urine screens, checklists or the transient effects of (cognitive-based) education (or training) are not the answer. This study highlights the need for nurses to engage meaningfully with this perceptibly 'difficult' group of patients.

RELEVANCE TO CLINICAL PRACTICE

The key aspects likely to contribute to problematic interactions with this patient cohort are outlined so that they can be prevented and, or addressed.