Advances in opioid therapy and formulations

Opioid analgesic dose and route conversion ratio studies: a scoping review to inform an eDelphi guideline

BACKGROUND

Clinicians regularly prescribe opioids to manage acute and chronic cancer pain, frequently to address acute postoperative pain, and occasionally to manage chronic non-cancer pain. Clinical efficacy may be suboptimal in some patients due to side effects and/or poor response, and opioid rotation/switching (conversions) is frequently necessary. Despite the widespread practice, opioid conversion ratios are inconsistent between clinicians, practices, and countries. Therefore, we performed a scoping systematic review of opioid conversion studies to inform an international eDelphi guideline.

METHODS

To ensure a comprehensive review, we conducted a systematic search across multiple databases (OVID Medline, PsycINFO, Embase, EBM-Cochrane Database of Systematic Reviews and Registered Trials, LILACS, IMEMR, AIM, WPRIM) using studies published up to June 2022. Additionally, we performed hand and Google Scholar searches to verify the completeness of our findings. Our inclusion criteria encompassed randomized and non-randomized studies with no age limit, with only a few pediatric studies identified. We included studies on cancer, non-cancer, acute, and chronic pain. The level and grade of evidence were determined based on the Multinational Supportive Care in Cancer (MASCC) criteria.

RESULTS

Our search yielded 21,118 abstracts, including 140 randomized (RCT) and 68 non-randomized (NRCT) clinical trials. We compared these results with recently published conversion ratios. Modest correlations were noted between published reviews and the present scoping systematic review.

CONCLUSION

The present scoping systematic review found low-quality evidence to support an opioid conversion guideline. We will use these data, including conversion ratios and type and route of administration, to inform an eDelphi guideline.

Effects of different electroacupuncture scheduling regimens on murine bone tumor-induced hyperalgesia: sex differences and role of inflammation

Previous studies have shown that electroacupuncture (EA) is able to reduce hyperalgesia in rodent models of persistent pain, but very little is known about the analgesic effects and potential sex differences of different EA treatment regimens. In the present study, we examined the effects of five different EA treatments on tumor-induced hyperalgesia in male and female mice. EA applied to the ST-36 acupoint either twice weekly (EA-2X/3) beginning on postimplantation day (PID) 3 or prophylactically three times prior to implantation produced the most robust and longest lasting antinociceptive effects. EA treatment given once per week beginning at PID 7 only produced an antinociceptive effect in female animals. The analgesic effect of EA-2X/3 began earlier in males, but lasted longer in females indicating sex differences in EA. We further demonstrate that EA-2X/3 elicits a marked decrease in tumor-associated inflammation as evidenced by a significant reduction in tumor-associated neutrophils at PID 7. Moreover, EA-2X/3 produced a significant reduction in tumor-associated PGE₂ as measured in microperfusate samples. Collectively, these data provide evidence that EA-2X/3 treatment reduces tumor-induced hyperalgesia, which is associated with a decrease in tumor-associated inflammation and PGE₂ concentration at the tumor site suggesting possible mechanisms by which EA reduces tumor nociception.

Barriers to pain management in the rehabilitation of the surgical oncology patient

Virtually every surgical oncology patient faces pain, and it can become a major barrier to rehabilitation and quality of life. Pain must be assessed as to its severity, etiology (somatic, visceral, or neuropathic), causation (directly from malignancy or from treatment side effects), and its impact on daily function. Treatments can include physical modalities, exercise, opioids, adjuvant medications, and interventional techniques. Barriers to treatment may include side effects, finances, and attitudes. New technologies in medication delivery systems, intrathecal pumps, injections, and surgery have greatly strengthened the armamentarium available to manage pain.

Pharmacological Management of Cancer Pain in the Elderly

Existing studies indicate a high prevalence rate and poor management of cancer pain in the elderly. Pain is often considered an expected concomitant of aging, and older patients are considered more sensitive to opioids. Despite the well known pharmacokinetic changes in the elderly, the complex network of factors involved in the opioid response make the evaluation of a single element, such as age, more difficult. Notwithstanding such difficulties, appropriate analgesic treatment is able to control cancer pain in the elderly in most cases. Skills necessary to optimise pain control in older cancer patients include the ability to objectively assess functional age (not necessarily related to chronological age since the rate of decline is variable), understand the impact of coexisting conditions, carefully manage the numbers and types of drugs taken at the same time and adequately communicate with patients and relatives. The most common treatment of cancer pain consists of the use of regularly given oral analgesics. The elderly are at increased risk of developing toxicity from NSAIDs, and the overall safety of these drugs in frail elderly patients should be considered. When older patients have clear contraindications to NSAIDs, manifest signs of toxicity from these agents, or find that pain is no longer controlled with this class of drugs, opioids should be started. A variety of opioids are available, and they differ widely with respect to analgesic potency and adverse effects among the elderly. Although the aged population requires lower doses of opioids, only careful titration based on individual response can ensure the appropriate response to clinical demand. Elderly patients are potentially more likely to be affected by opioid toxicity because of the physiological changes associated with aging. Nevertheless, appropriate dosage and administration may limit these risks. Cancer patients with pain who do not respond to increasing doses of opioids because they develop adverse effects before achieving acceptable analgesia may be switched to alternative opioids. Despite the favourable effects reported with opioid switching, monitoring is crucial, particularly in the elderly or patients who are switched from high doses of opioids. Adjuvant analgesics, including antidepressants, antiepileptics, corticosteroids and bisphosphonates may help in the treatment of certain types of chronic pain. With an appropriate and careful approach, it should be possible to reduce or eliminate unrelieved cancer pain in most elderly patients and, consequently, to enhance their quality of life. Older patients with cancer should be continuously assessed for cancer pain, both before and after analgesic treatment.