Not all pain syndromes are equally responsive to opioids (45). In cases in which a patient is physically dependent on opioids, as one would expect with prolonged use of this class of drug, it can sometimes be useful to consider the appropriateness of continuation of opioid therapy, especially when treatment goals of improved function and decreased pain remain unmet, despite aggressive opioid therapy.
Most pain is, to some degree, opioid responsive especially when the patient is opioid naive. As well, despite years of experience with opioid therapy, it remains unclear who will achieve a sustained opioid response for the treatment of chronic pain.
We know that chronic opioid therapy can reduce pain tolerance in certain individuals (46). The ability to control acute pain in the opioid-dependent individual as compared to the opioid-naive patient is much reduced. In studies looking at pain tolerance in MMT patients, there is a significant decrease in the ability of the MMT patients to tolerate a cold pressor model of neuropathic pain as compared to a matched control population (47). The continued use of opioids, in the absence of analgesic effect, is not without its cost.
When the patient and practitioner define the need to remain on opioid therapy not by how well the patient is doing but rather by how poorly things go whenever they try to reduce the dose, it may be time to reexamine the therapeutic role of opioids. When opioid levels in a physically dependent pain patient fall below a certain level, early withdrawal may occur. In the context of opioid abstinence induced hyperalgesia, it would be expected that the pain complaint should worsen (26). It is something of a myth that pain patients who no longer need opioids come off them easily.
We often see in MMT patients who present with addiction to short-acting, immediate-release opioids a dramatic 24-hour improvement in their pain relief with only once-daily dosing. This is despite the fact that we understand the duration of action of methadone as an analgesic is only six to eight hours (48). In this case, the dominant role of methadone may be to stabilize widely fluctuating opioid levels thereby reducing opioid withdrawal mediated hyperalgesia rather than acting as a primary analgesic.
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