Fentanyl tolerance in the treatment of cancer pain: a case of successful opioid switching from fentanyl to oxycodone at a reduced equivalent dose

Opioid Analgesia and Opioid-Induced Adverse Effects: A Review

Opioids are widely used as therapeutic agents against moderate to severe acute and chronic pain. Still, these classes of analgesic drugs have many potential limitations as they induce analgesic tolerance, addiction and numerous behavioural adverse effects that often result in patient non-compliance. As opium and opioids have been traditionally used as painkillers, the exact mechanisms of their adverse reactions over repeated use are multifactorial and not fully understood. Older adults suffer from cancer and non-cancer chronic pain more than younger adults, due to the physiological changes related to ageing and their reduced metabolic capabilities and thus show an increased number of adverse reactions to opioid drugs. All clinically used opioids are μ-opioid receptor agonists, and the major adverse effects are directly or potentially connected to this receptor. Multifunctional opioid ligands or peripherally restricted opioids may elicit fewer adverse effects, as shown in preclinical studies, but these results need reproducibility from further extensive clinical trials. The current review aims to overview various mechanisms involved in the adverse effects induced by opioids, to provide a better understanding of the underlying pathophysiology and, ultimately, to help develop an effective therapeutic strategy to better manage pain.

Covalently Loaded Naloxone Nanoparticles as a Long-Acting Medical Countermeasure to Opioid Poisoning

The mu opioid receptor antagonist naloxone has been a vital, long-standing countermeasure in the ongoing battle against opioid use disorders (OUD) and toxicity. However, due to its distinctive short elimination half-life, naloxone has shown diminished efficacy in cases of synthetic opioid poisoning as larger or repeated doses of the antidote have been required to achieve adequate reversal of severe respiratory depression and prevent episodes of renarcotization. This report describes the synthesis, characterization, and in vivo evaluation of a novel, nanoparticle-based naloxone formulation that provides extended protection against the toxic effects of the powerful synthetic opioid fentanyl. The strategy was predicated on a modified two-step protocol involving the synthesis and subsequent nanoprecipitation of a poly(lactic-co-glycolic acid) polymer scaffold bearing a covalently linked naloxone chain end (drug loading ∼7% w/w). Pharmacokinetic evaluation of the resulting covalently loaded naloxone nanoparticles (cNLX-NP) revealed an elimination half-life that was 34 times longer than high dose free naloxone (10 mg/kg) in male Sprague-Dawley rats. This enhancement was further demonstrated by cNLX-NP in subsequent in vivo studies affording protection against fentanyl-induced respiratory depression and antinociception for up to 48 h following a single intramuscular injection. These discoveries support further investigation of cNLX-NP as a potential therapeutic to reverse overdose and prevent renarcotization from fentanyl and its potent analogs.

Successful treatment of refractory cancer pain with morphine and ropivacaine: A case report

RATIONALE

Pain is one of the most common and distressing symptoms experienced by cancer patients. Cancer pain is a complex phenomenon with physical, psychological, social, and cognitive domains. Although opioids remain a cornerstone of cancer pain management, they are not effective in all patients. This case highlights the successful treatment of an opioid-refractory severe cancer pain crisis with ropivacaine infusion and subsequent rapid tapering of opioid dose.

PATIENT CONCERNS

This report illustrates the use of ropivacaine for cancer pain. A 62-year-old man with metastatic lung cancer was admitted to the hospital with uncontrolled chest-back and abdominal pain.

DIAGNOSES

The patient was diagnosed as refractory cancer pain.

INTERVENTIONS

Successful treatment with morphine and ropivacaine was performed to obtain longer opioid refractory severe cancer pain.

OUTCOMES

At 1, 3, and 6 months postoperative review, 70-75% relief of pain was achieved with overall activity was improved. The analgesic effect was stable during the 6-month follow-up period. No complications were reported during the follow-up period.

LESSONS

Our report demonstrates that ropivacaine is successful treatment for cancer pain in this case. It will supply us a novel navigation in cancer pain treatments. Meanwhile, this finding still needs additional study for confirmation.