Abstract
Dear Editor:
Methadone has an established role in the management of cancer pain, though there are concerns about the tolerability of subcutaneous methadone. 1
For patients reaching the end of life, an alternative to oral treatment will be needed. There is, however, a lack of evidence, and so no clear consensus on how this should be managed.
A semistructured questionnaire was sent out to all palliative care consultants in the Northern Deanery, United Kingdom (population 2.6 million), inquiring about their use of methadone for pain, their practice when patients are no longer able to take methadone orally, and any challenges they have encountered in this situation.
Twenty-one of 29 consultants (72%) responded. Of 14 doctors frequently prescribing methadone, 11 use a regular dosing schedule—the “Morley-Makin Method.” 2 Three use an “as required” (prn) schedule. 3 In the last year, 12 consultants looked after at least one patient who had been on oral methadone at the end of life. When patients were no longer able to swallow oral methadone, practice varied.
Concerned about the potential for skin reactions at the site of methadone injections, three consultants (21%) reverted to an alternative opioid given subcutaneously. This was initially administered prn and subsequently via continuous infusion, if needed. Few problems of inadequate pain control were reported, though rapid titration was occasionally required and multiple reviews to assess pain and side effects were often necessary.
Ten consultants (71%) used subcutaneous methadone, their rationale being that alternative opioids had been ineffective or intolerable in the past. The challenge of establishing appropriate conversions to alternative opioids was also a concern. Methadone's long half-life triggered difficulties in deciding whether to use a continuous infusion or intermittent injections. Nevertheless, problems of opioid toxicity or inadequate pain control were not reported using this method. Skin reactions, reported by four consultants, were unpredictable, idiosyncratic, and unrelated to dose or volume of injection.
Our questionnaire demonstrates that the management of patients established on oral methadone at the end of life is a relevant and prevalent issue. It also highlights variability of practice within one region.
National and international variability is also apparent. Palliativedrugs.com, 4 a commonly used online resource for palliative care practitioners, displays a number of different recommendations. Discrepancies include varying conversion factors from oral to subcutaneous methadone, inconsistencies in the indications for and doses of dexamethasone and hyaluronidase to reduce injection site irritation, and suggestions to use alternative opioids.
There is a paucity of evidence in the published data to guide dose conversions from methadone to alternatives; and opinions conflict as to the frequency, severity, and management of local toxicity. Pragmatic practice based on sound pharmacodynamic evidence, such as opportunistic use of the oral route, as well as consideration of the sublingual route, 5 may also play an important role.
In light of the increasing need to consider best practice in pain management at the end of life, a systematic review of current practice and field experience is justified as a forerunner to revising best practice guidelines.