Equianalgesic dose guidelines for long-term opioid use: Theoretical and practical considerations

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Clinical implications of short- and long-term use of opioids

Anesthesiologists are familiar with the use of opioids for short-term pain management during the perioperative period. Even with short-term use, there are wide variations in patient responses to opioid analgesics. A number of factors such as genetic differences in the response to pain, genetic variability amongst opioid receptors, and gender differences have been demonstrated to account for these differences.17, 18 Furthermore, tolerance, which is well known to occur with chronic opioid use,

Opioid rotation

Opioid rotation refers to the practice of changing from one opioid to another to improve pain control and/or reduce adverse effects and has recently been the subject of a number of extensive reviews.11, 16, 23, 24, 25, 26 Not all patients receiving opioids require opioid rotation. The incidence of opioid rotation in patients with chronic, nonmalignant pain has been reported as 32%,11 and it usually occurs for reasons related to inadequate pain relief. The occurrence of rotation is as high as

Strategies for overcoming tolerance

To counteract the effects of opioid tolerance, a number of strategies are employed. These include dose escalation, switching to alternative routes of administration, and opioid rotation. Drug rotation is an important strategy for managing poor opioid responsiveness, and the accuracy of conversion between agents and dosages is crucial to success.

Oral and subcutaneous

Established equianalgesic tables suggest that for the oral route, the EDR for morphine to hydromorphone is between 4:1 and 8:1 (30–60 mg of morphine = 7.5 mg of hydromorphone).1, 4

Recent studies have examined conversions between morphine and hydromorphone administered orally and subcutaneously. The EDR varies between 5:1 and 5.3:1 for conversions from morphine to hydromorphone for oral to oral and for subcutaneous to subcutaneous routes. When the drugs are switched in the opposite direction,

Recommendations for dose conversions

Converting patients from one opioid to another requires careful consideration, particularly if patients are opioid-tolerant or receiving high drug doses, and we recommend an approach that takes the adequacy of pain control into account. The equianalgesic table developed at our institution incorporates recent data concerning opioid conversions in patients on long-term therapy. Conversions should be relatively aggressive if the pain complaint is not well controlled; in these cases, patients are

Conclusions

Patients with chronic and cancer-related pain are frequently treated with high-dose opioids. It is not uncommon for patients to develop tolerance or severe adverse effects that require the substitution of another opioid. A number of pharmacodynamic and pharmacokinetic factors are responsible for wide variations in the older, established equianalgesic dose tables, and conversion from one long-term opioid to another must be undertaken with caution. The phenomenon of incomplete cross-tolerance may

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