McMaster University

Michael G. DeGroote
National Pain Centre

Scope of Search

Canadian Guideline for Safe and Effective Use of Opioids for Chronic Non-Cancer Pain

Cluster 3: Monitoring Long-Term Opioid Therapy (LTOT)

R13. Recommendation Statement

No. Recommendation Keyword


For patients experiencing unacceptable adverse effects or insufficient opioid effectiveness from one particular opioid, try prescribing a different opioid or discontinuing therapy (Grade B).

Switching or discontinuing opioids

  • R13. Discussion
  • R13. Summary of Peer-Reviewed Evidence

R13. Discussion

1. Switching Opioids

Because of unpredictable and incomplete cross-tolerance from one opioid to another, suggested initial doses of the new opioid are as follows:

If previous opioid dose was: Then, SUGGESTED new opioid dose is:
High 50% or less of previous opioid (converted to morphine equivalent)
Moderate or low 60–75% of the previous opioid (converted to morphine equivalent)

If switching to fentanyl, see Appendix B-8.1: Oral Opioid Analgesic Conversion Table.

There is no evidence to support the practice of combining different types of opioids.

2. Discontinuing Opioids

Opioids should be tapered and discontinued if the patient’s pain remains unresponsive after a trial of several different opioids. Patients who receive high opioid doses and remain incapacitated by pain should be considered treatment failures, even if the opioid “takes the edge off” the pain.

Patients sometimes report improvements in mood and pain reduction with tapering. The reason for this is not fully understood. With higher opioid doses, patients might experience withdrawal at the end of a dosing interval, which could heighten pain perception ("withdrawal-mediated pain"). Opioid tapering might relieve these withdrawal symptoms, thus decreasing pain perception. LTOT is known to cause hyperalgesia or pain sensitization, and lowering the opioid dose could reset the patient’s pain threshold (Baron 2006) — or it could be that patients’ mood and energy level improve with opioid tapering, so they do not focus on their pain as much.

The opioid should be tapered rather than abruptly discontinued. See Appendix B-12 for an opioid tapering protocol.

R13. Summary of Peer-Reviewed Evidence

1. Observational and uncontrolled studies have demonstrated that patients who have not responded to one opioid will sometimes respond when switched to a different opioid.

In 2004, Quigley conducted a Cochrane review on opioid switching to improve pain relief and drug tolerability. They found no randomized control trials. They included 23 case reports, 15 retrospective studies/audits and 14 prospective uncontrolled studies. The majority of the reports used morphine as first-line opioid and methadone as the most frequently used second-line opioid. All reports, apart from one, concluded that opioid switching is a useful clinical maneuver for improving pain control and/or reducing opioid-related side effects.

Quigley also concluded that more studies are needed to determine which opioid should be used first-line or second-line, and more research is needed to standardize conversion ratios when switching from one opioid to another.

2. Several observational studies have demonstrated that for patients with severe pain on high opioid doses, tapering results in improved reduced pain and improved mood.

Baron reported on a retrospective study of patients undergoing detoxification from high-dose opioids prescribed to treat an underlying chronic pain condition that had not resolved in the year prior. All patients were converted to ibuprofen to manage pain, with a subgroup treated with buprenorphine during detoxification. Self-reports for pain scores were taken at first evaluation, follow-up visits, and termination. Twenty-one of 23 patients reported a significant decrease in pain after detoxification, suggesting that high-dose opioids may contribute to pain sensitization via opioid-induced hyperalgesia, decreasing patient pain threshold and potentially masking resolution of the pre-existing pain condition (Baron 2006).

One study was conducted on over 356 patients with persistent pain and disability who attended a three-week cognitive behavioural program. Patients on opioids were tapered off. Pain decreased, and mood and functioning improved from baseline to discharge; the degree of improvement was the same in patients tapered off opioids as in patients who were not on opioids at baseline (Rome 2004).

One randomized trial demonstrated that patients attending an outpatient multidisciplinary pain program had improved pain ratings, psychological well-being, sleep and functioning, while their need for immediate-release opioid was also reduced (Becker 2000). Another study found that after a brief detoxification period, patients with both chronic pain and opioid dependence also report improved pain scores (Miller 2006).

Another trial reported success with opioid tapering, whether the tapering schedule was patient controlled reduction or staff controlled cocktail (Ralphs 1994). In both groups, 55% of the sample remained abstinent from opioids at six months.

One study demonstrated that multidisciplinary pain rehabilitation treatment incorporating analgesic medication withdrawal is associated with significant clinical improvements in physical and emotional functioning (Crisostomo 2008). A study on patients with fibromyalgia had similar results (Hooten 2007).

There are several limitations to these studies. The length of follow-up was short, up to six months. It is not known whether the outcomes were due to the tapering or to the psychological interventions the patients received. Nor is it known why tapering might improve pain perception.