A systematic review of the use of opioid medication for those with moderate to severe cancer pain and renal impairment: a European Palliative Care Research Collaborative opioid guidelines project

BACKGROUND

Opioid use in patients with renal impairment can lead to increased adverse effects. Opioids differ in their effect in renal impairment in both efficacy and tolerability. This systematic literature review forms the basis of guidelines for opioid use in renal impairment and cancer pain as part of the European Palliative Care Research Collaborative's opioid guidelines project.

OBJECTIVE

The objective of this study was to identify and assess the quality of evidence for the safe and effective use of opioids for the relief of cancer pain in patients with renal impairment and to produce guidelines.

SEARCH STRATEGY

The Cochrane Database of Systematic Reviews, Cochrane Central Register of Controlled Trials, MedLine, EMBASE and CINAHL were systematically searched in addition to hand searching of relevant journals.

SELECTION CRITERIA

Studies were included if they reported a clinical outcome relevant to the use of selected opioids in cancer-related pain and renal impairment. The selected opioids were morphine, diamorphine, codeine, dextropropoxyphene, dihydrocodeine, oxycodone, hydromorphone, buprenorphine, tramadol, alfentanil, fentanyl, sufentanil, remifentanil, pethidine and methadone. No direct comparator was required for inclusion. Studies assessing the long-term efficacy of opioids during dialysis were excluded.

DATA COLLECTION AND ANALYSIS

This is a narrative systematic review and no meta-analysis was performed. The Grading of RECOMMENDATIONS Assessment, Development and Evaluation (GRADE) approach was used to assess the quality of the studies and to formulate guidelines.

MAIN RESULTS

Fifteen original articles were identified. Eight prospective and seven retrospective clinical studies were identified but no randomized controlled trials. No results were found for diamorphine, codeine, dihydrocodeine, buprenorphine, tramadol, dextropropoxyphene, methadone or remifentanil.

CONCLUSIONS

All of the studies identified have a significant risk of bias inherent in the study methodology and there is additional significant risk of publication bias. Overall evidence is of very low quality. The direct clinical evidence in cancer-related pain and renal impairment is insufficient to allow formulation of guidelines but is suggestive of significant differences in risk between opioids.

RECOMMENDATIONS

RECOMMENDATIONS regarding opioid use in renal impairment and cancer pain are made on the basis of pharmacokinetic data, extrapolation from non-cancer pain studies and from clinical experience. The risk of opioid use in renal impairment is stratified according to the activity of opioid metabolites, potential for accumulation and reports of successful or harmful use. Fentanyl, alfentanil and methadone are identified, with caveats, as the least likely to cause harm when used appropriately. Morphine may be associated with toxicity in patients with renal impairment. Unwanted side effects with morphine may be satisfactorily dealt with by either increasing the dosing interval or reducing the 24 hour dose or by switching to an alternative opioid.

Lethal morphine intoxication in a patient with a sickle cell crisis and renal impairment: case report and a review of the literature

Morphine-6-glucuronide, the active metabolite of morphine, and to a lesser extent morphine itself are known to accumulate in patients with renal failure. A number of cases on non-lethal morphine toxicity in patients with renal impairment report high plasma concentrations of morphine-6-glucuronide, suggesting that this metabolite achieves sufficiently high brain concentrations to cause long-lasting respiratory depression, despite its poor central nervous system penetration. We report a lethal morphine intoxication in a 61-year-old man with sickle cell disease and renal impairment, and we measured concentrations of morphine and morphine-6-glucuronide in blood, brain and cerebrospinal fluid. There were no measurable concentrations of morphine-6-glucuronide in cerebrospinal fluid or brain tissue, despite high blood concentrations. In contrast, the relatively high morphine concentration in the brain suggests that morphine itself was responsible for the cardiorespiratory arrest in this patient. Given the fatal outcome, we recommend to avoid repeated or continuous morphine administration in renal failure.

Increased plasma morphine metabolites in terminally ill cancer patients with delirium: an intra-individual comparison

Delirium often causes severe distress for terminally ill cancer patients, and treatment of underlying pathologies is important to achieve symptom alleviation. Although accumulation of morphine metabolites may play an important role in development of delirium, empirical findings are conflicting due to a large inter-individual variation in morphine-related concentrations. To explore intra-individual changes of morphine metabolite concentrations before and after occurrence of terminal delirium, a prospective observational study was performed on terminally ill cancer patients. Among 131 consecutive hospice inpatients, 16 samples from 8 patients who received two blood samplings before and after development of delirium were analyzed. Delirium developed a median of 5 days before death, and clinical causes were attributed to multi-organ failure. Plasma concentrations of morphine-6-glucuronide (M-6-G) and morphine-3-glucuronide (M-3-G) significantly increased after development of delirium within the same patient. Mean normalized concentrations of M-6-G and M-3-G elevated from 1.24 +/- 1.06 to 2.94 +/- 3.52 ng/mL/mg (P = 0.016), and from 7.46 +/- 4.75 to 15.4 +/- 13.2 ng/mL/mg (P = 0.016), respectively. Normalized morphine concentration increased with a marginal statistical significance from 0.54 +/- 0.27 to 0.83 +/- 0.22 ng/mL/mg (P = 0.055). In conclusion, plasma concentrations of M-6-G and M-3-G were significantly higher after development of terminal delirium than before. It is suggested that accumulations of morphine metabolites can contribute to development of delirium in cancer patients whose death is impending.

Cancer pain management

Pain occurs in more than 80% of cancer patients before death. Because of the increase in the frequency of cancer deaths worldwide, it is imperative to address cancer pain as a public health problem. Until recently, educational efforts were focused on treatment issues rather than adequate assessment. The approach to pain intensity as a multidimensional construct has helped in focusing treatments and identifying prognostic factors. Valid tools have been developed that allow multidisciplinary assessment of these prognostic factors and their complex interrelationship with the analgesic response. As a result of increased opioid exposure, patients are currently developing newer toxicities, mostly central excitability including delirium, myoclonus, grand mal seizures, and hyperalgesia. The observation that more than 80% of patients will require alternate routes for opioid delivery before death led to the development of a number of novel and effective alternate routes for delivery. Finally, in recent years it has become evident that some specific pain syndromes need to be addressed using specific assessment and management techniques. Incidental pain, somatization, neuropathic pain, and cancer pain in patients with alcoholism and drug addiction are some of these syndromes.

Attitudes of Swiss physicians in prescribing opiates for cancer pain

Following clinical observations showing that opiates are sometimes not consistently administered for chronic cancer pain, a survey was conducted among 1200 physicians in the German-speaking part of Switzerland. Their opium-prescribing habits were assessed by means of a postal questionnaire. The results indicate that, among the majority of physicians completing the questionnaire, established guidelines and basic principles of pain control with opiates in cancer patients are largely understood. Oral morphine is chosen by 89% to initiate treatment of chronic cancer pain, and the correct use of slow-release morphine is known to 87% of the responding physicians. Unfortunately, an important minority of physicians does not follow established guidelines in the treatment of cancer pain, and up to 20% still feel that the danger of addiction, respiratory depression and other side-effects are important reasons for withholding opiates in this patient population. The results and their implications are discussed and compared with the current literature on cancer pain management.