Fentanyl-induced neurotoxicity and paradoxic pain

The impact of chronic fentanyl administration on the cerebral cortex in mice: Molecular and histological effects

PURPOSE

Fentanyl, a fully synthetic opioid, is widely used for severe pain management and has a huge abuse potential for its psychostimulant effects. Unlike other opioids, the neurotoxic effects of chronic fentanyl administration are still unclear. In particular, little is known about its effect on the cerebral cortex. The current study aims to test the chronic toxicity of fentanyl in the mice model.

METHODS

Adult male Balb/c mice were chronically treated with low (0.05 mg/kg, i.p) and high (0.1 mg/kg, i.p) doses of fentanyl for 5 consecutive weeks, and various neurotoxic parameters, including apoptosis, oxidative stress, and neuroinflammatory response were assessed in the cortex. Potential histological as well as neurochemical changes were also evaluated.

RESULTS

The results of this study show that chronic fentanyl administration induced intense levels of apoptosis, oxidative stress, and neuroinflammation in the cerebral cortex. These findings were found to be correlated with histopathological characteristics of neural degeneration and white matter injury. Moreover, fentanyl administration was found to reduce the expression of both NMDA receptor subunits and dopamine receptors and elevate the level of epidermal growth factor (EGF).

CONCLUSION

Fentanyl administration induced neurotoxic effects in the mouse cerebral cortex that could be primarily mediated by the evoked oxidative-inflammatory response. The altered expression of NMDA receptors, dopamine receptors, and EGF suggests the pernicious effects of fentanyl addiction that may end in the development of toxic psychosis.

Delirium and its Pharmacological Causes in Older People, Part Two

Delirium is a syndrome that can arise from many causes or underlying conditions, and though it has been reported in younger patients, it is more prevalent in older people, though it can occur in other age groups as well. Identifying delirium is challenging in older people because of the coexistence of underlying dementia or depression, which may further complicate the presentation. Drug-induced delirium is one of the major causes of delirium, and evaluation of this potential cause or contribution is an important component of the evaluation process, since it can lead to poor patient outcomes. Part one of this three part series reviewed the epidemiology, pathophysiology, evaluation, diagnostic process, and causes of delirium in older people, with a focus on the pharmacological causes. Part two of this series continues to review drugs and drug classes that can cause or contribute to delirium in older people.

Curing Opioid Toxicity with Intrathecal Targeted Drug Delivery

Pain is one of the most feared symptoms that concern cancer patients and their families. Despite well-established guidelines set forth by the World Health Organization (WHO) on the treatment of cancer pain, nearly half of cancer patients report poorly controlled pain. One of the most serious side effects of systemic oral opioid use is neurotoxicity, which is characterized by altered mental status and systemic neurologic impairments. Treatment strategies are supportive in nature and focused on reducing or changing the offending opioid and correcting any metabolic deficiencies. Herein, we discuss a case of opioid-induced neurotoxicity treated with intrathecal targeted drug delivery (TDD). The timing and implementation of advanced therapies such as intrathecal TDD is not well delineated. More importantly, patients and their oncologic providers are often unaware of this useful tool in treating challenging cancer-associated pain and significantly minimizing systemic opioid side effects. To ensure that patients have comprehensive oncologic care, best-practice guidelines suggest involvement of an interdisciplinary team and coordinated care. Early referral to a pain and palliative specialist may allow for improved patient outcomes and removal of unnecessary barriers to optimal patient care.

Hydromorphone-induced chorea as an atypical presentation of opioid neurotoxicity: A case report and review of the literature

BACKGROUND

While opioid-induced myoclonus is well described, there are limited reports of opioid-induced chorea. Here we present the first case of chorea as a manifestation of opioid neurotoxicity due to hydromorphone.

CASE PRESENTATION

A 20-year-old woman presenting with fevers and cutaneous lesions was diagnosed with hemophagocytic lymphohistiocytosis secondary to primary cutaneous lymphoma. Surgical resection of a cutaneous lesion was complicated by severe postoperative pain requiring rapid opioid dose escalation. Seven days after hydromorphone was initiated, she developed positive myoclonus, hallucinations, delirium, and involuntary, flowing movements consistent with chorea. She had no personal or family history of nervous system disorders and was not taking any medications associated with drug-induced chorea. Case management: The remainder of her neurologic examination was unremarkable. Her renal function was normal and no etiology was found on neuroimaging or laboratory workup. Hydromorphone was discontinued and pain control was achieved with fentanyl. Case outcome: The patient's neurotoxic symptoms including chorea resolved within 72 h of hydromorphone discontinuation.

CONCLUSION

Further studies are needed to determine which patients have a unique sensitivity to opioids predisposing them to chorea. Clinicians should be aware that chorea may be a sign of such toxicity so that rapid corrective action can be taken.

Opioid-induced Hallucinations: A Review of the Literature, Pathophysiology, Diagnosis, and Treatment

Despite their association with multiple adverse effects, opioid prescription continues to increase. Opioid-induced hallucination is an uncommon yet significant adverse effect of opioid treatment. The practitioner may encounter patient reluctance to volunteer the occurrence of this phenomenon because of fears of being judged mentally unsound. The majority of the literature concerning opioid-induced hallucinations arises from treatment during end-of-life care and cancer pain. Because the rate of opioid prescriptions continues to increase in the population, the rate of opioid-associated hallucinations may also conceivably increase. With a forecasted increase in the patient-to-physician ratio, opioid therapy is predicted to be provided by practitioners of varying backgrounds and medical specialties. Hence, knowledge of the pharmacology and potential adverse effects of these agents is required. This review seeks to increase awareness of this potential complication through a discussion of the literature, potential mechanisms of action, diagnosis, and treatment strategies.

Toward a systematic approach to opioid rotation

Patients requiring chronic opioid therapy may not respond to or tolerate the first opioid prescribed to them, necessitating rotation to another opioid. They may also require dose increases for a number of reasons, including worsening disease and increased pain. Dose escalation to restore analgesia using the primary opioid may lead to increased adverse events. In these patients, rotation to a different opioid at a lower-than-equivalent dose may be sufficient to maintain adequate tolerability and analgesia. In published trials and case series, opioid rotation is performed either using a predetermined substitute opioid with fixed conversion methods, or in a manner that appears to be no more systematic than trial and error. In clinical practice, opioid rotation must be performed with consideration of individual patient characteristics, comorbidities (eg, concurrent psychiatric, pulmonary, renal, or hepatic illness), and concurrent medications, using flexible dosing protocols that take into account incomplete opioid cross-tolerance. References cited in this review were identified via a search of PubMed covering all English language publications up to May 21, 2013 pertaining to opioid rotation, excluding narrative reviews, letters, and expert opinion. The search yielded a total of 129 articles, 92 of which were judged to provide relevant information and subsequently included in this review. Through a review of this literature and from the authors’ empiric experience, this review provides practical information on performing opioid rotation in clinical practice.

Neuropsychiatric side effects due to a transdermal fentanyl patch: hallucinations

Opioid analgesics are used commonly in end-stage cancer patients for pain treatment. Central nervous system adverse effects are rare. A73-year-old female patient was admitted to the emergency department for auditory and visual hallucinations. The patient had been receiving palliative treatment for liver, cervical, and lumbar bone metastases from an unknown origin. The patient used a transdermal fentanyl patch for palliative pain management and metoclopramide hydrochloride for nausea and vomiting. The patient had suffered weight loss of 10 kg within 5 months, and laboratory findings revealed hypoalbuminemia. The patient was considered to have experienced a fentanyl overdose, and the transdermal fentanyl patch treatment was stopped. The hallucinations improved during follow-up, and the patient was discharged with a dose adjustment. End-stage cancer patients with weight loss and hypoalbuminemia may be more prone to opioid adverse effects, such as hallucinations. The dose of fentanyl must be adjusted for weight loss, and correction of hypoalbuminemia may also lower the incidence of such adverse effects.

Medication-overuse headache and opioid-induced hyperalgesia: A review of mechanisms, a neuroimmune hypothesis and a novel approach to treatment

Introduction

Patients with chronic headache who consume large amounts of analgesics are often encountered in clinical practice. Excessive intake of analgesics is now considered to be a cause, rather than simply a consequence, of frequent headaches, and as such the diagnosis “medication-overuse headache” (MOH) has been formulated. Despite the prevalence and clinical impact of MOH, the pathophysiology behind this disorder remains unclear and specific mechanism-based treatment options are lacking.

Discussion

Although most acute headache treatments have been alleged to cause MOH, here we conclude from the literature that opioids are a particularly problematic drug class consistently associated with worsening headache. MOH may not be a single entity, as each class of drug implicated may cause MOH via a different mechanism. Recent evidence indicates that chronic opioid administration may exacerbate pain in the long term by activating toll-like receptor-4 on glial cells, resulting in a pro-inflammatory state that manifests clinically as increased pain. Thus, from the available evidence it seems opioid-overuse headache is a phenomenon similar to opioid-induced hyperalgesia, which derives from a cumulative interaction between central sensitisation, due to repeated activation of nociceptive pathways by recurrent headaches, and pain facilitation due to glial activation.

Conclusion

Treatment strategies directed at inhibiting glial activation may be of benefit alongside medication withdrawal in the management of MOH.

Role of gabapentin in preventing fentanyl- and morphine-withdrawal-induced hyperalgesia in rats

PURPOSE

This study was undertaken to examine the effect of gabapentin for preventing hyperalgesia induced by morphine and fentanyl withdrawal in rats.

METHODS

To induce hyperalgesia, Sprague Dawley (SD) rats were subcutaneously injected with fentanyl four times at 15-min intervals (60 μg/kg per injection), resulting in total dose of 240 μg/kg over 1 h, and morphine 10 mg/kg twice daily for 7 days. The effect of gabapentin was detected with behavioral tail-flick and paw-withdrawal tests.

RESULTS

Drug termination produced significant decrease in antinociception thresholds (P < 0.05 vs. saline group), indicating that the rats became sensitive to thermal stimuli. In rats that received combined treatment with fentanyl/morphine and gabapentin (25/50 mg/kg), results demonstrated that there were no significant decreases in antinociception thresholds (vs. saline group) after opioid withdrawal. Gabapentin (50 mg/kg) could also prevent morphine tolerance. The 50% effective dose (ED50) value was 12.5 mg/kg in tail-flick and 13.6 mg/kg in paw-withdrawal tests.

CONCLUSIONS

The study showed that gabapentin can significantly prevented opioid-induced hyperalgesia (OIH) induced caused by fentanyl and morphine, suggesting a role for the addition of gabapentin in the perioperative period and during chronic pain treatment as an effective drug to prevent OIH.

Lasting developmental effects of neonatal fentanyl exposure in preweanling rats

The present study aimed to determine whether neonatal treatment with fentanyl has lasting effects on stressed developing brain. Six-day-old rats were assigned to one of three groups (10 males/group): (1) fentanyl (incision+fentanyl), (2) saline (incision+0.9% saline), and (3) unoperated (unoperated sham). Pups with a plantar paw incision received repetitive subcutaneous injections of fentanyl or vehicle through postnatal days (PNDs) 6 to 8. A nonoperated sham group served as nonstressed control. Studies included assessment of development from PND 6 to PND 21 (growth indices and behavioral testing). Fentanyl administered twice daily for three days after surgical incision had no impact on early growth and development, as measured on PND 9, but showed a lasting impact on later growth, enhanced behavioral development, and lower anxiety, as measured through PNDs 10–21. While this does not completely support a benefit from such treatment, our findings may contribute to support the neonatal use of fentanyl, when indicated, even in premature newborns.

[High-dose buprenorphine for outpatient palliative pain therapy]

The case of a 78-year-old patient with cancer-related pain and additionally mixed-pain syndrome is presented. Pain therapy with buprenorphine TTS 210 microg/h every 3 days was sufficient in the beginning, later the therapy was changed because of increasing problems of tape fixing during fever periods under chemotherapy to a continuous infusion of buprenorphine intravenously via an external medication pump. During the course of therapy it became necessary to increase the dose to 99.9 mg/day buprenorphine. Under this medication a sufficient pain reduction (median NRS 2-3) over a period of 135 days could be achieved. At the same time the patient was vigilant and cooperative without signs of intoxication until the end of life at home in the presence of his family.If no signs of intoxication occur under extreme opioid therapy and a sufficient pain therapy can be achieved, a rotation to another opioid is not necessary. However, outpatient palliative care requires a frequent adaptation to the individually varying opioid demand of the patient and time-consuming nursing care.