Reversible delirium during opiod switching from transdermal fentanyl to methadone

WITHDRAWN: Opioid switching to improve pain relief and drug tolerability

The original authors were unable to complete an update of this review. A new protocol is in preparation with a new author team, who have revised the title. Publication of the new protocol is expected in 2014 with the title 'Opioid switching for cancer pain in adults'.

At November 2015, the new author team are no longer available to complete the replacement protocol. Please contact the PaPaS CRG for more information.

The editorial group responsible for this previously published document have withdrawn it from publication.

Breakthrough pain in cancer patients

Breakthrough pain is a transient exacerbation of pain that occurs either spontaneously or in relation to a specific predictable or unpredictable trigger, despite relatively stable and adequately controlled background pain. A typical episode of breakthrough pain has a fast onset and short duration, yet despite the self-limiting nature of each breakthrough pain, the repeated episodes can have a significant effect on patients' quality of life. Normal-release oral opioids have been the mainstay pharmacological approach for patients who are receiving an around the clock opioid regimen, but the onset and duration of action of oral opioids such as morphine may not be suitable for treating many breakthrough pains. Efforts to provide non-parenteral opioid formulations that could provide more rapid, and more effective, relief of breakthrough pain have led to the development of transmucosal opioid formulations.

Opioid switching from transdermal fentanyl to oral methadone in patients with cancer pain

BACKGROUND

Patients with cancer often are rotated from other opioids to methadone to improve the balance between analgesia and side effects. To the authors' knowledge, no clear guidelines currently exist for the safe and effective rotation from transdermal fentanyl to methadone.

METHODS

The authors evaluated a protocol for switching opioid from transdermal fentanyl to oral methadone in 17 patients with cancer. Reasons for switching were uncontrolled pain (41.1% of patients) and neurotoxic side effects (58.9% of patients). Methadone was initiated 8-24 hours after fentanyl withdrawal, depending on the patient's previous opioid doses (from < 100 microg per hour to > 300 microg per hour). The starting methadone dose was calculated according to a 2-step conversion between transdermal fentanyl:oral morphine (1:100 ratio) and oral morphine:oral methadone (5:1 ratio or 10:1 ratio). The correlation between previous fentanyl dose and the final methadone dose or the fentanyl:methadone dose ratio was assessed by means of Pearson and Spearman correlation coefficients (r), respectively. A Friedman test was used to compare pain intensity before and after the switch and the use of daily rescue doses.

RESULTS

Opioid rotation was fully or partially effective in 80% and 20%, respectively, of patients with somatic pain. Neuropathic pain was not affected by opioid switching. Delirium and myoclonus were reverted in 80% and 100% of patients, respectively, after opioid switching. A positive linear correlation was obtained between the fentanyl and methadone doses (Pearson r, 0.851). Previous fentanyl doses were not correlated with the final fentanyl:methadone dose ratios (Spearman r, - 0.327).

CONCLUSIONS

The protocol studied provided a safe approach for switching from transdermal fentanyl to oral methadone, improving the balance between analgesia and side effects in patients with cancer.

Opioid switching to improve pain relief and drug tolerability

BACKGROUND

Patients with cancer, and increasingly chronic non-cancer pain frequently require strong opioids for pain relief. Morphine is the first-line strong opioid of choice for these patients. While most achieve adequate analgesia with morphine, a significant minority either suffer intolerable side-effects, inadequate pain relief, or both. For these patients switching to an alternative opioid is becoming established clinical practice. However, the evidence for the effectiveness of opioid switching does not appear to be established.

OBJECTIVES

The aim of this review was to investigate the usefulness of opioid switching for patients with pain.

SEARCH STRATEGY

Randomised trials that assessed opioid rotation, switching, or substitution in adults or children with acute or chronic pain were sought through electronic databases and by handsearching relevant journals. Date of the most recent search: January 2003.

SELECTION CRITERIA

The search strategy retrieved no randomised controlled trials, and therefore no studies were available to enable a quantitative synthesis that would assess the effectiveness of the strategy of opioid switching.

DATA COLLECTION AND ANALYSIS

Given the lack of RCTs, the review examined all case reports, uncontrolled, and retrospective studies in an attempt to determine the current level of evidence.

MAIN RESULTS

Fifty-two reports were identified, comprising 23 case reports, 15 retrospective studies/audits and 14 prospective uncontrolled studies. The majority of the reports used morphine as first-line opioid and the most frequently used second-line opioid was methadone. All reports, apart from one, concluded that opioid switching is a useful clinical manoeuvre for improving pain control and/or reducing opioid-related side-effects.

REVIEWERS' CONCLUSIONS

For patients with inadequate pain relief and intolerable opioid-related toxicity/adverse effects, a switch to an alternative opioid may be the only option for symptomatic relief. However, the evidence to support the practice of opioid switching is largely anecdotal or based on observational and uncontrolled studies. Randomised trials, including 'N of 1' studies, where a patient acts as their own control, are needed: firstly, to establish the true effectiveness of this clinical practice; secondly, to determine which opioid should be used first-line or second-line; and thirdly, to standardise conversion ratios when switching from one opioid to another.

Management of opioid side effects in cancer-related and chronic noncancer pain: a systematic review

Side effects can limit opioid dosage and reduce quality of life. The purpose of this systematic review was to assess the management of opioid side effects in the context of cancer pain management or, in the event that no evidence was available for cancer pain, for chronic noncancer pain. The side effects studied were constipation, pruritus, nausea and vomiting, myoclonus, sedation, respiratory depression, and delirium. Opioid rotation to manage side effects was also studied. For each side effect, we searched MEDLINE and the Cochrane Controlled Trials Register and identified 657 possible titles for inclusion. Of these, 67 studies met inclusion criteria for analysis. The lack of well-designed, randomized controlled trials and the heterogeneity of populations and study designs made the drawing of firm conclusions difficult and precluded performance of meta-analysis. The type, strength, and consistency of evidence for available interventions to manage opioid side effects vary from strong (eg, on the use of naloxone to reverse respiratory depression or constipation) to weak (eg, changing from the oral to epidural route of morphine administration to manage sedation). Well-designed trials in the specified populations are required to furnish clinicians with secure evidence on managing opioid side effects successfully.

Pharmacotherapy of cancer-related episodic pain

Episodic pain is a transient increase in pain intensity over background pain. Episodic pain occurs commonly in cancer patients; it is a heterogeneous phenomenon that is incapacitating, debilitating and can have a significant impact on quality of life. Episodic pain can be difficult to manage; it is often unpredictable, typically of fast onset, of short duration and feels similar to background pain except that it may be more severe. The successful management of episodic pain can only be achieved following a thorough assessment. The subsequent management usually involves both pharmacological and non-pharmacological strategies integrated into the overall care and appropriate for the stage of the patient's disease. Pharmacological management includes the implementation of primary therapies (e.g., chemotherapy for the underlying aetiology of the pain, optimising the scheduled medication (e.g., analgesics and adjuvant analgesics) and specific pharmacological interventions for the episodic pain (e.g., rescue medication).