Opioid therapy for chronic pain has been popularized over the past few decades, and a concern has arisen that the analgesic efficacy of opioids is not always maintained over prolonged courses of treatment despite dose escalation and stable pain. Considering the potentially serious adverse effects of opioids, the idea that pain relief could diminish over time may have a significant impact on the decision to embark on this therapy, especially in vulnerable individuals. Possible loss of analgesic efficacy is especially concerning, considering that dependence may make it hard to withdraw opioid therapy even in the face of poor analgesia. This article first reviews the evidence on opioid efficacy when used for the treatment of chronic pain, and concludes that existing evidence suggests that analgesic efficacy, although initially good, is not always sustained during continuous and long-term opioid therapy (months to years). The theoretical basis for loss of analgesic efficacy over time is then examined. Mechanisms for loss of analgesic efficacy proposed are pharmacologic tolerance, opioid-induced hyperalgesia, subtle and intermittent withdrawal, and a number of psychologic factors including loss of the placebo component.

Purpose The ability to identify and focus care to patients at higher risk of moderate to severe postoperative pain should improve analgesia and patient satisfaction, and may affect reimbursement. We undertook this multi-centre crosssectional study to identify preoperative risk factors for moderate to severe pain after total hip (THR) and knee (TKR) replacement. Methods A total of 897 patients were identified from electronic medical records. Preoperative information and anaesthetic technique was gained by retrospective chart review. The primary outcomes were moderate to severe pain (pain score ≥4/10) at rest and with activity on postoperative day one. Logistic regression was performed to identify predictors for moderate to severe pain. Results Moderate to severe pain was reported by 20 % at rest and 33 % with activity. Predictors for pain at rest were female gender (OR 1.10 with 95 % CI 1.01-1.20), younger age (0.96, 0.94-0.99), increased BMI

Persistent postsurgical pain is common after THR and TKR and is associated with reduced health-related quality of life, although our survey may be biased by the low response rate and retrospective recall bias. Nonmodifiable risk factors may lead to risk stratification. Severity of acute postoperative pain may be a modifiable risk factor.