Overview of managing acute pain in opioid-tolerant patients

Opioid-tolerant patients need additional consideration for the management of acute pain. Opioid analgesic effects decrease over time so higher doses are needed to obtain the same analgesic effect.

Additional considerations are needed when managing acute pain in:

Seek specialist advice early.

Opioid tolerance is often accompanied by opioid-induced hyperalgesia (increased sensitivity to pain) and physical dependence (risk of opioid withdrawal upon abrupt cessation or dose reduction), see Neuroadaptive and physiological changes associated with opioid use for further advice on neuroadaptive and physiological changes associated with opioid use. Underestimation and undertreatment of pain is common. Treatment should aim to provide effective analgesia while preventing withdrawal from the patient’s long-term opioid.

The patient’s previous experiences of poorly managed acute pain can make them distrustful of staff. Clinicians should explain to patients that, in their situation:

effective pain relief might be more difficult
a multimodal analgesic approach may be required
there are harms and benefits of initiating additional opioids.

There is limited evidence to guide management of acute pain in opioid-tolerant patients.

The general principles of acute pain management are relevant to opioid-tolerant patients; however, additional considerations are required if an additional opioid is initiated. Always consider nonpharmacological options and nonopioid analgesics (eg paracetamol, nonsteroidal anti-inflammatory drugs [NSAIDs], local anaesthetics) before adding an opioid. Low-dose ketamine infusions (specialist only) may improve analgesia, attenuate tolerance and reduce additional opioid requirements.

When possible, continue the patient’s long-term prescribed opioid to prevent withdrawal. Verify the dose of opioid that the patient is taking (from an independent source) before it is prescribed and use the patient’s usual route of administration and dose regimen. Specialist input may be required if a different opioid or route of administration is required (eg if the patient is unable to take oral medication), or if their usual dose cannot be verified.

Seek early advice from a pain specialist or acute pain service if an opioid is required (eg for moderate or severe acute nociceptive pain). An immediate-release opioid may be initiated on an ‘as- required’ basis in addition to the patient’s usual long-term opioid. Opioid requirements vary greatly between patients and may be significantly higher in opioid-tolerant patients than opioid-naive patients. Patient-controlled analgesia (PCA) may be a useful technique in opioid-tolerant patients. The recommended initial dose of immediate-release opioid is approximately one-sixth to one-tenth of the patient’s total usual daily opioid dose. Alternatively, use the opioid doses recommended here for moderate acute nociceptive pain, or here for severe acute nociceptive pain. Additional opioid doses should be titrated according to the patient’s functional activity and sedation score; pain scores are less useful because they often remain higher in opioid-tolerant patients.

If additional opioids are added to a patients medication regimen, opioid-tolerant patients may have an increased risk of opioid-induced ventilatory impairment compared to opioid-naive patients; however, the incidence of nausea and vomiting may be lower.

Once the acute illness or injury has resolved, additional opioid doses should be tapered and stopped, preferably without altering the patient’s usual long-term opioid regimen. The patient’s general practitioner must be involved to ensure appropriate follow-up and regular analgesic review.