Formulations of fentanyl for the management of pain

Balancing acts: The dual faces of fentanyl in medicine and public health

Fentanyl is a potent synthetic opioid widely used in medicine for its effective analgesic properties, particularly in surgical procedures and in the treatment of severe, chronic pain. In recent decades, however, there has been a worrying increase in the illicit use of fentanyl, particularly in North America. This rise in illicit use is concerning because fentanyl is associated with polydrug abuse, which adds layers of complexity and dangerous. This review provides a comprehensive examination of fentanyl, focusing on its synthesis and medical use. It also discusses the significance of the piperidine ring in medicinal chemistry as well as the critical role of fentanyl in pain management and anesthesia. Furthermore, it addresses the challenges associated with the abuse potential of fentanyl and the resulting public health concerns. The study aims to strike a balance between the clinical benefits and risks of fentanyl by advocating for innovative uses while addressing public health issues. It examines the chemistry, pharmacokinetics and pharmacodynamics of fentanyl and highlights the importance of personalized medicine in the administration of opioids. The review underscores the necessity of continuous research and adaptation in both clinical use and public health strategies.

Comparative Analysis of Nebulized Versus Intravenous Fentanyl for Pain Control After Tonsillectomy: A Double-Blind, Randomized, Controlled Trial

OBJECTIVES

Effective posttonsillectomy analgesia is crucial for patient comfort and recovery. Fentanyl, notable for its potency, rapid action, and lipophilicity, has been successfully used in various procedures through multiple administration routes. However, the use of its nebulized form for posttonsillectomy pain has not been extensively explored. This study sought to compare the analgesic efficacy, onset time, and complications between nebulized and intravenous fentanyl in posttonsillectomy patients.

METHODS AND METHODS

In this randomized controlled trial, adult patients who underwent tonsillectomy were assigned to either an intravenous fentanyl group (1 mcg/kg) or a nebulized fentanyl group (4 mcg/kg). In both groups, fentanyl was administered when pain scores exceeded three. Pain levels were monitored every 5 minutes until they fell below four. The study also recorded the duration until the next analgesia request and noted complications (such as respiratory depression, bradycardia, chest tightness, drowsiness, nausea, pruritus, sweating, and flushing) within 24 hours. Patient exclusions were based on predetermined criteria.

RESULTS

From an initial cohort of 59 patients, 22 in the intravenous group and 27 in the nebulizer group were eligible for analysis after applying the exclusion criteria. The nebulizer group exhibited a significantly prolonged period before the next analgesia request, with a median of 683.5 minutes (interquartile range 260-1440), in contrast to the 326.7 minutes (145.0-504.7) observed in the intravenous group (P = .009). The time to achieve a pain score less than 4 and the incidence of side effects did not differ significantly between the groups.

CONCLUSION

Nebulized fentanyl provided a longer duration of analgesia than intravenous fentanyl in posttonsillectomy pain management, with similar onset times and side effect profiles. These findings underscore the potential of nebulized fentanyl as an effective alternative for pain control in posttonsillectomy patients.

Evolution of Fentanyl Prescription Patterns and Administration Routes in Primary Care in Salamanca, Spain: A Comprehensive Analysis from 2011 to 2022

(1) Background: The escalating use of opioids contributes to social, health, and economic crises. In Spain, a notable surge in the medical prescription of opioids in recent years has been observed. The aim of this work was to assess the consumption rate of fentanyl, categorised by the different administration routes, in Primary Care in the province of Salamanca (Spain) spanning the years 2011 to 2022, and to compare it with the national trend and with data from the US. (2) Methods: Doses per inhabitant per day (DHD) were calculated, and interannual variations, as well as consumption rates, were subject to thorough analysis. (3) Results: The prevalence of fentanyl use in Salamanca has doubled from 1.21 DHD in 2011 to 2.56 DHD in 2022, with the transdermal system (TD) as the predominant administration route. This upward trajectory mirrors the national trend, yet the rise in fentanyl use is markedly lower than the reported data in the US. This finding may be attributed to an ageing population and potentially inappropriate fentanyl prescriptions, i.e., for the management of chronic non-cancer pain and other off-label prescriptions. (4) Conclusions: The use of fentanyl in Salamanca, particularly through transdermal systems, doubled from 2011 to 2022, aligning with the national trend. Preventive measures are imperative to prevent fentanyl misuse and moderate the observed escalation in consumption rates.

Fentanyl and its derivatives: Pain-killers or man-killers?

Fentanyl is a synthetic μ-opioid receptor agonist approved to treat severe to moderate pain with faster onset of action and about 100 times more potent than morphine. Over last two decades, abuse of fentanyl and its derivatives has an increased trend, globally. Currently, the United States (US) faces the most serious situation related to fentanyl overdose, commonly referred to as the opioid epidemic. Nowadays, fentanyl is considered as the number one cause of death for adults aged 18-45 in the US. Synthesis and derivatization of fentanyl is inexpensive to manufacture and easily achievable. Indeed, more than 1400 fentanyl derivatives have been described in the scientific literature and patents. In addition, accessibility and efficacy of fentanyl and its derivatives can play a potential role in misuse of these compounds as a chemical weapon. In this review, the properties, general pharmacology, and overdose death cases associated with fentanyl and selected derivatives are presented. Moreover, current opioid epidemic in the US, Moscow theatre hostage crisis, and potential misuse of fentanyl and its derivatives as a chemical weapon are disclosed.

Fentanyl in cancer pain management: avoiding hasty judgments and discerning its potential benefits

Cancer pain is an important challenge in treatment and requires a rapid onset of action for its control. In particular, breakthrough cancer pain (BTcP) should be adequately controlled with a stable dose of a short-acting oral opioid. Fentanyl is a synthetic, highly selective opioid with many advantageous chemical properties, including high lipophilicity and distinct pharmacokinetic properties. It is recommended for pain management in a variety of settings, including acute pain, chronic pain and BTcP. To date, its variously designed formulations allow non-invasive administration; amongst others, sublingual fentanyl has proven useful in the management of BTcP and in improving the quality of life of patients with cancer. This review provides an update on the management of BTcP with fentanyl, with consideration of safety, as it remains an important tool in the treatment of cancer pain.

Effects of Transdermal Fentanyl Treatment on Acute Pain and Inflammation in Rats with Adjuvant-induced Monoarthritis

Eliminating unnecessary pain is an important requirement of performing animal experimentation, including reducing and controlling pain of animals used in pain research. The goal of this study was to refine an adjuvant-induced monoarthritis model in rats by providing analgesia with a transdermal fentanyl solution (TFS). Male and female Sprague-Dawley rats, single- or pair-housed, were injected with 20 μL of complete Freund adjuvant (CFA) into the left ankle joint. CFA-injected rats treated with a single dose of transdermal fentanyl solution (0.33 or 1 mg/kg) were compared with an untreated CFA-injected group and sham groups that received either no treatment or TFS treatment (1 mg/kg) during 72 h. At the tested doses, TFS reduced mechanical hyperalgesia and improved the mobility, stance, rearing, and lameness scores at 6 h after CFA injection. Joint circumferences were not reduced by TFS treatment, and no significant differences were detected between the 2 doses of TFS, or between single- and pair-housed rats. Treatment with TFS did not appear to interfere with model development and characteristics. However, overall, the analgesic effect was transient, and several opioid-related side effects were observed.

In vivo pharmacokinetic analyses of placental transfer of three drugs of different physicochemical properties in pregnant rats

Although the use of medication during pregnancy is common, information on exposure to the developing fetus and potential teratogenic effects is often lacking. This study used a rat model to examine the placental transfer of three small-molecule drugs with molecular weights ranging from approximately 300 to 800 Da with different physicochemical properties. Time-mated Sprague Dawley (Hsd:SD) rats aged 11-13 weeks were administered either glyburide, rifaximin, or fentanyl at gestational day 15. Maternal blood, placentae, and fetuses were collected at 5 min, 30 min, 1 h, 4 h, 8 h, 24 h, 48 h, and 96 h post-dose. To characterize the rate and extent of placental drug transfer, we calculated several pharmacokinetic parameters such as maximum concentration (Cmax), time to maximum concentration (Tmax), area under the concentration-time curve (AUC), half-life (t_1/2), clearance (CL), and volume of distribution (Vd) for plasma, placenta, and fetus tissues. The results indicated showed that fetal exposure was lowest for glyburide, accounting for only 2.2 % of maternal plasma exposure as measured by their corresponding AUC ratio, followed by rifaximin (37.9 %) and fentanyl (172.4 %). The fetus/placenta AUC ratios were found to be 10.7 % for glyburide, 11.8 % for rifaximin, and 39.1 % for fentanyl. These findings suggest that although the placenta acts as a protective shield for the fetus, the extent of protection varies for different drugs and depends on factors such as molecular weight, lipid solubility, transporter-mediated efflux, and binding to maternal and fetal plasma proteins.

Stress reveals a specific behavioral phenotype for opioid abuse susceptibility

Susceptibility to stress has long been considered important for the development of substance use disorders. Nonetheless, behavioral and physiological responses to stress are highly variable, making it difficult to identify the individuals who are most likely to abuse drugs. In the present study, we employed a comprehensive battery of tests for negative valence behaviors and nociception to identify individuals predisposed to opioid seeking following oral opioid self-administration. Furthermore, we examined how this profile was affected by a history of stress. We observed that mice receiving foot shock stress failed to exhibit a preference for sucrose, showed increased immobility in the forced swim task, and exhibited mechanical hypersensitivity when compared to controls. When considering these behaviors in light of future fentanyl-seeking responses, we observed that heightened mechanical sensitivity corresponded to higher opioid preference in mice with a history of stress, but not controls. Moreover, we were surprised to discover that paradoxically high sucrose preferences predicted fentanyl preference in shock mice, while signs of anhedonia predicted fentanyl preference in controls. Taken together, these results indicate that stress can act as a physiological modulator, shifting profiles of opioid abuse susceptibility depending on an individual's history.

Pediatric Sedation and Analgesia Outside the Operating Room: Combining Intranasal Fentanyl and Inhaled Nitrous Oxide

OBJECTIVE

Combining intranasal fentanyl (IN FENT) with inhaled nitrous oxide (N2O) seems to have good properties for pediatric procedural sedation and analgesia (PSA). This study aims to assess the side effect rate of the combined use of IN FENT and N2O.

METHODS

We performed a retrospective, single-center study. Patients treated in either the pediatric emergency department (PED) or the pediatric surgery outpatient clinic (PSOC) were included, if they received PSA with IN FENT and nitrous oxide with 50% oxygen (N2O 50%).

RESULTS

Three hundred seventy-five patients were included over a period of 4 years. Median age was 9.4 years (range, 3.1 to 15.9) and 39% of patients were female. Overall side effect rate was 30% (114 patients). Most frequent was dizziness (n = 63, 17%; 95% CI, 13–21), followed by nausea (n = 23, 6%; 95% CI, 4–9) and emesis (n = 14, 4%; 95% CI, 2–6), with 35 patients having either nausea and/or emesis (9%; 95% CI, 7–13). No serious side effects were recorded (0%; 95% CI, 0–0.1). Of 298 patients with information regarding satisfaction, 280 patients would like the same sedation for a similar procedure in the future (94%; 95% CI, 90–96). We found no relation between previously described risk factors and emesis and/or nausea.

CONCLUSIONS

N2O 50% combined with IN FENT can be recommended as an effective and safe treatment in the PED and the PSOC. While the side effect rate, primarily dizziness, nausea and emesis was substantial, antiemetic prophylaxis is not indicated owing to the overall low incidence of nausea and emesis.

Visible-Light-Induced α,γ-C(sp3)-H Difunctionalization of Piperidines

Herein, we describe a novel protocol for visible-light-induced α,γ-C(sp³)-H difunctionalization of piperidines. This redox-neutral, atom-economical protocol, which exhibits a broad substrate scope and good functional group compatibility, constitutes a concise, practical method for constructing piperidine-containing bridged-ring molecules. Preliminary mechanistic studies indicated that highly regioselective activation of the inert γ-C(sp³)-H bond of piperidines was achieved through a 1,5-hydrogen atom transfer reaction of a nitrogen radical generated in situ.

In Vitro and In Vivo Analysis of Fentanyl and Fentalog Metabolites using Hyphenated Chromatographic Techniques: A Review

Fentanyl and fentanyl analogues (also called fentalogs) are used as medical prescriptions to treat pain for a long time. Apart from their pharmaceutical applications, they are misused immensely, causing the opioid crisis. Fentanyl and its analogues are produced in clandestine laboratories and sold over dark Web markets to different parts of the world, leading to a rise in the death rate due to drug overdose. This is because the users are unaware of the lethal effects of the newer forms of fentalogs. Unlike other drugs, these fentalogs cannot be detected easily, as very little data are available, and this is one of the major reasons for the risk of life-threatening poisoning or deaths. Hence, rigorous studies of these drugs and their possible metabolites are required. It is also necessary to develop techniques for the detection of minute traces of metabolites in biological fluids. This Review provides an overview of the application of hyphenated chromatographic techniques used to analyze multiple novel fentalogs, using in vivo and in vitro methods. The article focuses on the metabolites formed in phase I and phase II processes in biological specimens obtained in recent cases of drug abuse and overdose deaths that could be useful for the detection and differentiation of multiple fentalogs.

Transdermal Fentanyl Uptake at Two Different Patch Locations in Swiss White Alpine Sheep

Simple Summary

Providing adequate and prolonged pain relief to sheep undergoing invasive orthopedic surgery while keeping side effects and stress for the animals at a minimum is challenging. Transdermal patches continuously releasing the synthetic opioid fentanyl through the skin, are a frequently used method in veterinary and human medicine. To refine the current analgesia protocol, we compared the uptake of fentanyl from a transdermal fentanyl patch applied at two different skin locations in sheep. The fentanyl plasma levels were measured at different time points over five days. The patch applied on the foreleg resulted in a faster fentanyl uptake with higher peaks and a longer time within or above the target fentanyl plasma concentration when compared to the one on the thorax. Additionally, it was easier to apply the patch at the foreleg than at the thorax. Our findings suggest that the fentanyl patch should be applied to the foreleg 3–6 h before the painful insult and that its effect should last at least 48 h.

Abstract

When using animals in biomedical research, investigators have the responsibility to ensure adequate analgesia. Currently, transdermal fentanyl patches (TFP) are often used to provide postoperative analgesia in large laboratory animals. The aim of this study was to compare the fentanyl uptake resulting from TFP applied at two different locations, namely the foreleg and the thorax, in healthy adult sheep. Twelve sheep received a TFP with an intended dosage of 2 ug/kg/h. Blood samples were taken at different time points over a period of five days and the fentanyl plasma levels were measured. The TFP applied on the foreleg allowed a faster fentanyl uptake with higher peaks and a longer time within or above the target concentration of 0.6–1.5 ng/mL, shown to be analgesic in humans, when compared to the one on the thorax. Assuming that the effective plasma concentration described for humans is providing analgesia in sheep as well, the present findings suggest that it should be sufficient to apply the TFP 3–6 h before the painful insult and that its effect should last at least 48 h. Furthermore, when TFP are used to provide postoperative analgesia in sheep, they should be placed on the foreleg rather than on the thorax.

Neuromodulation Management of Chronic Neuropathic Pain in The Central Nervous system

Neuromodulation is becoming one of the clinical tools for treating chronic neuropathic pain by transmitting controlled physical energy to the pre-identified neural targets in the central nervous system. Its nature of drug-free, non-addictive and improved targeting have attracted increasing attention among neuroscience research and clinical practices. This article provides a brief overview of the neuropathic pain and pharmacological routines for treatment, summarizes both the invasive and non-invasive neuromodulation modalities for pain management, and highlights an emerging brain stimulation technology, transcranial focused ultrasound (tFUS) with a focus on ultrasound transducer devices and the achieved neuromodulation effects and applications on pain management. Practical considerations of spatial guidance for tFUS are discussed for clinical applications. The safety of transcranial ultrasound neuromodulation and its future prospectives on pain management are also discussed.

Evaluation of Analgesic Patches in Cynomolgus Macaques (Macaca fascicularis)

Opioids are widely used in veterinary and human medicine to manage pain. However, there is a paucity of information in the literature regarding the pharmacokinetics of opioid transdermal patches (TDP) in NHP. Therefore, to determine whether opioid TDP attain therapeutic concentrations in NHP, the pharmacokinetics of fentanyl (25 μg/h) and buprenorphine (10 and 20 μg/h) TDP were evaluated in naïve, adult, male cynomolgus macaques (n = 4) in a crossover study. Plasma opioid levels were determined by tandem liquid chromatography-mass spectrometry. The AUC_0-inf for fentanyl and the low and high dose buprenorphine patches were 115 ± 14, 462 ± 74, and 778 ± 344 ng× h/mL, and the plasma half-lifes were 22 ± 4, 77 ± 27, and 42 ± 11 h, respectively. No adverse effects were noted throughout the study. Minimal therapeutic concentrations for fentanyl (0.2 ng/mL) and buprenorphine (0.1 ng/mL) were achieved in all macaques within 8 h of fentanyl and 24 h of buprenorphine TDP application. Therapeutic levels for the fentanyl and low- and high-dose buprenorphine patches were maintained for 96, 120, and 144 h, respectively. These findings suggest that 25-μg/h fentanyl patches should be replaced every 4 d, and the low- and high-dose buprenorphine patches should be replaced every 5 and 6 d, respectively. The results of this study show that fentanyl and buprenorphine patches achieve minimal therapeutic levels for clinically relevant periods of time and should be considered viable options for pain management in cynomolgus macaques.

Prevalence and characteristics of breakthrough cancer pain in an outpatient clinic in a Catalan teaching hospital: incorporation of the Edmonton Classification System for Cancer pain into the diagnostic algorithm

BACKGROUND

Breakthrough cancer pain (BTcP) is defined according to its principal characteristics: high intensity, short time interval between onset and peak intensity, short duration, potential recurrence over 24 h and non-responsiveness to standard analgesic regimes. The Edmonton Classification System for Cancer Pain (ECS-CP) is a classification tool that evaluates different dimensions of pain. The aim of this study was to measure prevalence and the main characteristics of BTcP in a sample of advanced cancer patients and to explore the complexity observed when ECS-CP is incorporated into BTcP diagnostics algorithm.

METHODS

Descriptive prevalence study (Retrospective chart review). Davies' algorithm was used to identify BTcP and ECS-CP was used to recognize appropriate dimensions of pain. The study was conducted in a sample of advanced cancer patients attending hospital outpatient clinic in Lleida, Spain. 277 patients were included from 01/01/2014 to 31/12/2015. No direct contact was made with participants. The following information was extracted from the palliative care outpatient clinic database: age, gender, civil status, cognitive impairment status, functional performance status and variables related to tumour. Only BTcP cases were included.

RESULTS

Prevalence of BTcP was 39.34% (63.9% men). Mean of age was 68.2 years. Main diagnosis was lung cancer (n = 154; 31.6%). Metastases were diagnosed in 83% of the sample. 138 patients (49.8%) were diagnosed with 1 type of BTcP and 139 (50.2%) were diagnosed with more than one type of BTcP. In total, 488 different types of BTcP were recorded (mean 1.75 ± 0, 9), 244 of these types (50%) presented a component of neuropathic pain. Addictive behaviour, measured through CAGE test, was present in 29.2% (N = 81) of the patients and psychological distress was present in 40.8% (n = 113).

CONCLUSIONS

Prevalence of BTcP (39.34%) is similar to the one reflected in the existing literature. Study results indicate that the routine use of ECS-CP in a clinical setting allows us to detect more than one type of BTcP as well as additional complexity associated with pain (neuropathic, addictive behavior and psychological distress).

A Comparison of Oral Midazolam-ketamine, Dexmedetomidine-fentanyl, and Dexmedetomidine-ketamine Combinations as Sedative Agents in Pediatric Dentistry: A Triple-Blinded Randomized Controlled Trial

Introduction:

It is common to encounter a patient who is anxious to the magnitude that precludes the possibility of provision of dental treatment. This study aims to evaluate and compare the sedative effect of oral combinations of midazolam-ketamine (MK), dexmedetomidine-fentanyl (DF), and dexmedetomidine-ketamine (DK) in a group of uncooperative children requiring dental treatment.

Methodology:

This was a prospective, randomized, triple-blind study where 36 children who were 3–9 year old with American Society of Anesthesiologists –I status and presenting early childhood caries were randomly assigned to: Group A – 0.3 mg/kg of M and 5 mg/kg K, Group B – 2 ug/kg of D with 3 ug/kg of F, and Group C – 2ug/kg of D with 5 mg/kg of K in 1 mL honey. Patients' blood pressure, heart rate, and oxygen saturation were recorded from the start of the procedure till discharge. Patients' behavior, sedation status, and wake-up behavior were evaluated with Modified Observer Assessment of Alertness and Sedation Scale and ease of treatment completion by Houpt scale.

Results:

Hemodynamic changes were statistically insignificant in all three groups. 72.8% of patients in Group A and 58.3% of patients in Group B were successfully sedated during treatment. Behavior improvement was seen in all three groups during treatment with statistically insignificant difference in behavior scores produced by Group C. Ease of treatment completion was moderately better with Group A.

Conclusion:

Oral DK has a comparable sedative property with oral MK combination. Oral DF promises to be a potential sedative agent for children due to its successful anxiolysis.

Review of Intranasally Administered Medications for Use in the Emergency Department

BACKGROUND

Intranasal (IN) medication delivery is a viable alternative to other routes of administration, including intravenous (IV) and intramuscular (IM) administration. The IN route bypasses the risk of needle-stick injuries and alleviates the emotional trauma that may arise from the insertion of an IV catheter.

OBJECTIVE

This review aims to evaluate published literature on medications administered via the IN route that are applicable to practice in emergency medicine.

DISCUSSION

The nasal mucosa is highly vascularized, and the olfactory tissues provide a direct conduit to the central nervous system, bypass first-pass metabolism, and lead to an onset of action similar to IV drug administration. This route of administration has also been shown to decrease delays in drug administration, which can have a profound impact in a variety of emergent scenarios, such as seizures, acutely agitated or combative patients, and trauma management. IN administration of midazolam, lorazepam, flumazenil, dexmedetomidine, ketamine, fentanyl, hydromorphone, butorphanol, naloxone, insulin, and haloperidol has been shown to be a safe, effective alternative to IM or IV administration. As the use of IN medications becomes a more common route of administration in the emergency department setting, and in prehospital and outpatient settings, it is increasingly important for providers to become more familiar with the nuances of this novel route of medication delivery.

CONCLUSIONS

IN administration of the reviewed medications has been shown to be a safe and effective alternative to IM or IV administration. Use of IN is becoming more commonplace in the emergency department setting and in prehospital settings.

Fentanyl Inhibits Tumorigenesis from Human Breast Stem Cells by Inducing Apoptosis

Fentanyl is an opioid analgesic that it is widely used in cancer patients. Since there have been reports of effects of analgesic medications on the recurrence and development of resistance to treatment, influences of of fentanyl on MCF-7 and HEK293 cells were evaluated. Cell viability and apoptosis were assessed by MTT assay and flow cytometry, respectively. Gene expression analysis was performed by quantitative real-time PCR assay for the Oct4, Sox2 and Nanog genes as stem cell markers and Bax, Bcl2, and p53 genes as apoptosis markers. MTT assay results showed that fentanyl significantly inhibited the growth of MCF-7 cells in a dose-and time-dependent manner while significantly increasing apoptosis. In contrast, decrease was noted in HEK-293 cells. In MCF-7 derived cancer stem cells, fentanyl treatment decreased the expression of Bax, Bcl2, Oct4, Sox2, Nanog genes when compared to untreated cells. In HEK-293 stem cells, decrease was noted for Sox2, Nanog and Bax, but increase for Oct4. Our study supports an antitumor role of fentanyl by inducing apoptosis and reducing numbers of cancer stem cells in the MCF-7 human breast adenocarcinoma line.

A review of factors explaining variability in fentanyl pharmacokinetics; focus on implications for cancer patients

Fentanyl is a strong opioid that is available for various administration routes, and which is widely used to treat cancer-related pain. Many factors influence the fentanyl pharmacokinetics leading to a wide inter- and intrapatient variability. This systematic review summarizes multiple studied factors that potentially influence fentanyl pharmacokinetics with a focus on implications for cancer patients. The use of CYP3A4 inhibitors and inducers, impaired liver function, and heating of the patch potentially influence fentanyl pharmacokinetics in a clinically relevant way. In elderly patients, current data suggest that we should carefully dose fentanyl due to alterations in absorption and metabolism. The influence of BMI and gender on fentanyl pharmacokinetics is questionable, most probably due to a large heterogeneity in the published studies. Pharmacogenetics, e.g. the CYP3A5*3 gene polymorphism, may influence fentanyl pharmacokinetics as well, although further study is warranted. Several other factors have been studied but did not show significant and clinically relevant effects on fentanyl pharmacokinetics. Unfortunately, most of the published papers that studied factors influencing fentanyl pharmacokinetics describe healthy volunteers instead of cancer patients. Results from the studies in volunteers may not be simply extrapolated to cancer patients because of multiple confounding factors. To handle fentanyl treatment in a population of cancer patients, it is essential that physicians recognize factors that influence fentanyl pharmacokinetics, thereby preventing potential side-effects and increasing its efficacy.

Efficacy of fentanyl transdermal patch in pain control after lower third molar surgery: A preliminary study

Background

Surgical removal of impacted lower third molars is a common oral surgical procedure, generally followed by moderate to severe postoperative pain. Transdermal drug delivery as a concept offers interesting possibilities for postoperative pain control. The aim of this study was to evaluate the efficacy of transdermal system with fentanyl in relieving pain following impacted lower third molar surgery.

Material and Methods

Seventeen patients with bilateral impacted lower third molars were included in this preliminary study. For postoperative pain control, patients randomly received a fentanyl patch plus placebo tablet after the first operation and regular (placebo) patch and an analgesic, after the second operation. Analgesia was evaluated during first 24 hours postoperatively according to patients’ reports about time of first pain appearance and additional analgesic consumption. Pain severity was rated using a 10 cm long visual analogue scale (VAS).

Results

Intensity of postoperative pain and postoperative analgesic consumption were significantly lower after the Fentanyl Transdermal System (FTS) was applied (p<0.05). Duration of postoperative analgesia was significantly higher with FTS when compared to control treatment (p<0.05).

Conclusions

Based on the results of this preliminary study, transdermal system with fentanyl significantly reduced postoperative pain after third molar surgery.

Key words:Analgesia, fentanyl, transdermal administration, third molar surgery, acute pain, postoperative care.

Nebulized Fentanyl in Acute Pain: A Systematic Review

OBJECTIVE

To provide a systematic review of the current role of nebulized fentanyl in acute pain and potentially other conditions.

DATA SOURCES

A MEDLINE literature search inclusive of the dates 1946 to May 2016 was performed using the following search terms: fentanyl and administration, inhaled Excerpta Medica was searched from 1980 to May 2016 using the following search terms: exp fentanyl/inhalation drug administration Additionally, Web of Science was searched using the terms fentanyl and pain inclusive of 1945 to May 2016.

STUDY SELECTION AND DATA EXTRACTION

We utilized the Preferred Reporting Items for Systematic Reviews and Meta-analyses (PRISMA) guidelines to select English language, human primary literature, review articles, and supporting data assessing the efficacy of nebulized fentanyl in acute pain.

DATA SYNTHESIS

Seven clinical trials have demonstrated no difference in efficacy between nebulized fentanyl and intravenous (IV) opioids. Few adverse effects were reported; however, the trials were of short duration. Nebulized fentanyl appeared to be a rapid-acting analgesic that does not require IV access.

CONCLUSION

Evidence suggests that nebulized fentanyl is as effective as IV opioids in the treatment of acute pain, with relatively few adverse effects. However, questions remain about the extemporaneous preparation of fentanyl nebulized solution, the variability in nebulization devices, and ensuring consistent drug delivery to distal airways in the clinical setting. The abuse potential of nebulized fentanyl should also be considered.

Safety and efficacy of intranasally administered medications in the emergency department and prehospital settings

PURPOSE

The safety and efficacy of medications that may be administered via the intranasal route in adult patients in the prehospital and emergency department (ED) settings are reviewed.

SUMMARY

When medications of appropriate molecular character and concentration are delivered intranasally, they are quickly transported across this capillary network and delivered to the systemic circulation, thereby avoiding the absorption-limiting effects of first-pass metabolism. Therapeutic drug concentrations are rapidly attained in the cerebrospinal fluid, making intranasal administration a very effective mode of delivery. To optimize the bioavailability of intranasally administered drugs, providers must minimize the barriers to absorption, minimize the volume by maximizing the concentration, maximize the absorptive surface of the nasal mucosa, and use a delivery system that maximizes drug dispersion and minimizes drug runoff. Medications can be instilled into the nasal cavity with syringes or droppers by applying a few drops at a time or via atomization. The intranasal route of administration may be advantageous for patients who require analgesia, sedation, anxiolysis, termination of seizures, hypoglycemia management, narcotic reversal, and benzodiazepine reversal in the ED or prehospital settings. Medications that have been studied in the adult population include fentanyl, sufentanil, hydromorphone, ketamine, midazolam, haloperidol, naloxone, flumazenil, and glucagon. The available data do indicate, however, that intranasal administration may be a safe, effective, and well tolerated route of administration.

CONCLUSION

Based on the published literature, intranasal administration of fentanyl, sufentanil, ketamine, hydromorphone, midazolam, haloperidol, naloxone, glucagon, and, in limited cases, flumazenil may be a safe, effective, and well-tolerated alternative to intramuscular or intravenous administration in the prehospital and ED settings.

An overview of treatment approaches for chronic pain management

Pain which persists after healing is expected to have taken place, or which exists in the absence of tissue damage, is termed chronic pain. By definition chronic pain cannot be treated and cured in the conventional biomedical sense; rather, the patient who is suffering from the pain must be given the tools with which their long-term pain can be managed to an acceptable level. This article will provide an overview of treatment approaches available for the management of persistent non-malignant pain. As well as attempting to provide relief from the physical aspects of pain through the judicious use of analgesics, interventions, stimulations, and irritations, it is important to pay equal attention to the psychosocial complaints which almost always accompany long-term pain. The pain clinic offers a biopsychosocial approach to treatment with the multidisciplinary pain management programme; encouraging patients to take control of their pain problem and lead a fulfilling life in spite of the pain.

Pharmacodynamics and clinical efficacy of fentanyl iontophoretic transdermal system for post-operative pain in hospitalized patients

INTRODUCTION

The fentanyl iontophoretic transdermal system (ITS) is a patient-controlled transdermal system allowing needle-free administration of on-demand doses of Fentanyl of 40 µg over a 10-min period up to 80 doses or over a 24-h period. It is indicated in opioid naïve patients for the treatment of acute postoperative pain in the hospitalized patients for up to 72 h.

AREAS COVERED

It has been demonstrated to be effective and safe in randomized trials and to provide comparable analgesia versus morphine intravenous (i.v.) patient-controlled analgesia (PCA) with adverse events similar between groups.

EXPERT OPINION

Fentanyl ITS has shown high patient satisfaction rates, and was described by patients and investigators as easy and convenient to use. These properties make this technology interesting when considering perioperative pain management. In the present health care environment additional data are required to establish the cost-benefit ratio of this technology in optimizing patient's recovery from surgery.

Saliva versus Plasma for Pharmacokinetic and Pharmacodynamic Studies of Fentanyl in Patients with Cancer

PURPOSE

Fentanyl is widely used to relieve cancer pain. However there is great interpatient variation in the dose required to relieve pain and little knowledge about the pharmacokinetic and pharmacodynamic (PK/PD) relationship of fentanyl and pain control. Patients with cancer are fragile and there is reluctance on the part of health professionals to take multiple plasma samples for PK/PD studies. The relationship between plasma and saliva fentanyl concentrations was investigated to determine whether saliva could be a valid substitute for plasma in PK/PD studies.

METHODS

One hundred sixty-three paired plasma and saliva samples were collected from 56 patients prescribed transdermal fentanyl (Durogesic, Janssen-Cilag Pty Limited, NSW, Australia) at varying doses (12-200 µg/h). Pain scores were recorded at the time of sampling. Fentanyl and norfentanyl concentrations in plasma and saliva were quantified using HPLC-MS/MS.

FINDINGS

Saliva concentrations of fentanyl (mean = 4.84 μg/L) were much higher than paired plasma concentrations of fentanyl (mean = 0.877 μg/L). Both plasma and saliva mean concentrations of fentanyl were well correlated with dose with considerable interpatient variation at each dose. The relationship between fentanyl and norfentanyl concentrations was poor in both plasma and saliva. No correlation was observed between fentanyl concentration in plasma and saliva (r(2) = 0.3743) or free fentanyl in plasma and total saliva concentrations (r(2) = 0.1374). Pain scores and fentanyl concentration in either of the matrices were also not correlated.

IMPLICATIONS

No predictive correlation was observed between plasma and saliva fentanyl concentration. However the detection of higher fentanyl concentrations in saliva than plasma, with a good correlation to dose, may allow saliva to be used as an alternative to plasma in PK/PD studies of fentanyl in patients with cancer.

Transmucosal Immediate-Release Fentanyl for Breakthrough Cancer Pain: Opportunities and Challenges for Use in Palliative Care

Opioids are used to treat breakthrough cancer pain (BTCP) and can be classified by relative duration and onset of action. Regulatory approvals of numerous transmucosal immediate-release fentanyl (TIRF) formulations provide alternative options to palliative care-trained providers in the management of BTCP. TIRFs have been formulated as a sublingual tablet, sublingual spray, intranasal spray, pectin-based nasal spray, buccal tablet, and buccal soluble film. Differences exist between TIRFs regarding formulation design and dosing to treat BTCP. Opportunities for use include palliation of BTCP in head and neck cancer and/or radiation-induced mucositis. The purpose of this review is to discuss TIRF formulation and dosing, pharmacokinetics, clinical efficacy, patient acceptability, and safety/tolerability. In addition, barriers to TIRF utilization will be discussed.

Fentanyl iontophoretic transdermal system versus morphine intravenous patient-controlled analgesia for pain management following gynecological surgery: a meta-analysis of randomized, controlled trials

AIM

To compare the efficacy and safety of patient-controlled fentanyl iontophoretic transdermal system (ITS) with morphine intravenous (i.v.) patient-controlled analgesia (PCA) for pain management following gynecological surgery.

METHODS

Two-open-label, multicenter, randomized, active-controlled, parallel-group studies (n = 1142) were conducted that compared fentanyl ITS with morphine iv. PCA for postoperative pain. The subgroup of gynecological surgery patients from each trial was utilized for this meta-analysis (n = 604). Of these patients, 295 received fentanyl ITS (40 μg/dose) and 309 received morphine i.v. PCA (1 mg/dose) for up to 72 h. Efficacy measures included the patient global assessment (PGA) and the investigator global assessment (IGA) of the method of pain control.

RESULTS

Gynecological surgery patients (n = 604) included in this meta-analysis had a mean age of 45 years, were predominantly Caucasian (65%) and had a mean body mass index of 29 mg/kg2. There were statistically significantly more patients treated with fentanyl ITS and more investigators who rated their pain control method as 'excellent' on the PGA at 24 h (49.3 vs 37.4%, respectively; p = 0.0029) and IGA at the last assessment (59.5 vs. 38.0%, respectively; p < 0.0001), respectively, compared with morphine iv. PCA at the last assessment.

CONCLUSION

Following gynecological surgery, patients and investigators were more satisfied (had a higher percent of an 'excellent' rating on the PGA and IGA, respectively) with fentanyl ITS than morphine iv. PCA as a method of pain control.

Quantitative determination of fentanyl in newborn pig plasma and cerebrospinal fluid samples by HPLC-MS/MS

In this study, a selective and sensitive high performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS) method requiring low sample volume (≤100 μL) was developed and validated for the quantitative determination of the opioid drug fentanyl in plasma and cerebrospinal fluid (CSF). A protein precipitation extraction with acetonitrile was used for plasma samples whereas CSF samples were injected directly on the HPLC column. Fentanyl and (13) C6 -fentanyl (Internal Standard) were analyzed in an electrospray ionization source in positive mode, with multiple reaction monitoring (MRM) of the transitions m/z 337.0/188.0 and m/z 337.0/105.0 for quantification and confirmation of fentanyl, and m/z 343.0/188.0 for (13) C6 -fentanyl. The respective lowest limits of quantification for plasma and CSF were 0.2 and 0.25 ng/mL. Intra- and inter-assay precision and accuracy did not exceed 15%, in accordance with bioanalytical validation guidelines. The described analytical method was proven to be robust and was successfully applied to the determination of fentanyl in plasma and CSF samples from a pharmacokinetic and pharmacodynamic study in newborn piglets receiving intravenous fentanyl (5 µg/kg bolus immediately followed by a 90-min infusion of 3 µg/kg/h).

Pain management of the cancer patient

INTRODUCTION

Cancer pain is one of the most important symptoms of malignant disease, which has a major impact on the quality of life of cancer patients. Therefore, it needs to be treated appropriately after a careful assessment of the types and causes of pain.

AREAS COVERED

The mainstay of cancer pain management is systemic pharmacotherapy. This is, in principle, still based on the WHO guidelines initially published in 1986. Although these have been validated, they are not evidence-based. The principles are a stepladder approach using non-opioids, weak and then strong opioids. In addition, adjuvants can be added at any step to address specific situations such as bone or neuropathic pain. Patients, even if they are on long-acting opioids, need to be provided with immediate-release opioids for breakthrough pain. In case of inefficacy or severe adverse effects of one opioid, rotation to another opioid is recommended.

EXPERT OPINION

There is a major need for more and better randomized controlled trials in the setting of cancer pain as the lack of evidence is hampering the improvement of current treatment guidelines.

Plasticity of α2-adrenergic spinal antinociception following nerve injury: selective, bidirectional interaction with the delta opioid receptor

Interactions of opioid receptors with other receptor families can be made use of to improve analgesia and reduce adverse effects of opioid analgesics. We investigated interactions of the α2-adrenergic receptor (α2AR) with opioid receptors of the mu (MOR) and delta (DOR) types in the spinal dorsal horn in an animal model of neuropathic pain induced by spinal nerve ligation. Nine days after nerve injury, immunoreactivity for the α2AR subtype A (α2AAR) was increased both in tissue homogenates and at pre- and post-synaptic sites in transverse sections. The efficacy of spinally administered α2AAR agonist guanfacine at reducing C-fiber-evoked field potentials was increased in nerve-ligated rats. This reducing effect was impaired by simultaneous administration of DOR antagonist naltrindole, but not MOR antagonist CTOP, suggesting that concurrent DOR activation was required for α2AAR-mediated inhibition. While DOR agonist deltorphin II and MOR agonist DAMGO both effectively depressed C-fiber-evoked spinal field potentials, DOR- but not MOR-mediated depression was enhanced by subclinical guanfacine. In conscious, nerve-ligated rats, chronically administered deltorphin II produced stable thermal and mechanical antinociception over the 9 following days after nerve injury without apparent signs of habituation. Such an effect was dramatically enhanced by co-administration of a low dose of guanfacine, which reversed thermal and mechanical thresholds to levels near those prior to injury. The results suggest that spinal, α2AAR-mediated antinociception is increased after nerve injury and based on DOR co-activation. We demonstrate in vivo that α2AAR/DOR interaction can be exploited to provide effective behavioral antinociception during neuropathic pain.

[Management of postoperative pain in ear-nose-throat surgery]

The degree of pain following different types of ear-nose-throat surgery varies greatly and must be adjusted on an individual basis. Post-operative pain therapy can be classified into basic pain therapy and additive pain therapy (as needed). Effective pain therapy can lead to lower morbidity and to considerable economic advantages. The subjective pain intensity experienced by patient should be the basis for the dose adaptation and is essential for rapid recovery.

Fentanyl-related compounds and derivatives: current status and future prospects for pharmaceutical applications

Fentanyl and its analogs have been mainstays for the treatment of severe to moderate pain for many years. In this review, we outline the structural and corresponding synthetic strategies that have been used to understand the structure-biological activity relationship in fentanyl-related compounds and derivatives and their biological activity profiles. We discuss how changes in the scaffold structure can change biological and pharmacological activities. Finally, recent efforts to design and synthesize novel multivalent ligands that act as mu and delta opioid receptors and NK-1 receptors are discussed.

Thermal sensitivity across ages and during chronic fentanyl administration in rats

RATIONALE

Chronic pain is becoming a more common medical diagnosis and is especially prevalent in older individuals. As such, prescribed use of opioids is on the rise, even though the efficacy for pain management in older individuals is unclear.

OBJECTIVES

Thus, the present preclinical study assessed the effectiveness of chronic fentanyl administration to produce antinociception in aging rats (16, 20, and 24 months).

METHODS

Animals were tested in a thermal sensitivity procedure known to involve neural circuits implicated in chronic pain in humans. Sensitivity to heat and cold thermal stimulation was assessed during 28 days of fentanyl administration (1.0 mg/kg/day), and 28 days of withdrawal.

RESULTS

Fentanyl resulted in decreased thermal sensitivity to heat but not cold stimulation indicated by more time spent in the hot compartment relative to time spent in the cold or neutral compartments. Unlike previous findings using a hot-water tail withdrawal procedure, tolerance did not develop to the antinociceptive effects of fentanyl over a 28-day period of drug administration. The oldest animals were least sensitive, and the youngest animals most sensitive to the locomotor-stimulating effects of fentanyl. The effect on the antinociceptive response to fentanyl in the oldest group of rats was difficult to interpret due to profound changes in the behavior of saline-treated animals.

CONCLUSIONS

Overall, aging modifies the behavioral effects of opioids, a finding that may inform future studies for devising appropriate treatment strategies.

Pain management for the cancer patient - current practice and future developments

Anaesthesiologists will be asked to provide pain management for cancer patients in the absence of more specialised services, when interventional techniques are indicated and in the postoperative period. In all these settings, the complexity of cancer pain and its psychosocial connotations need to be considered to provide appropriate and holistic care. Principles of systemic pain management, effective in most patients, continue to follow established guidelines; identification of neuropathic pain and its appropriate treatment is important here. Interventional pain relief is required in a minority of cancer patients, but it should be considered when appropriate and then done with best available expertise. Neurolytic procedures have lost importance here over the years. Postoperative pain management should be multimodal with consideration of regional techniques when applicable. In managing postoperative pain in cancer patients, opioid tolerance needs to be addressed to avoid withdrawal and poor analgesia. Preventive techniques aiming to reduce chronic postoperative pain should be considered.

Fentanyl for the treatment of tumor-related breakthrough pain

BACKGROUND

Breakthrough cancer pain (BTCP) is common among cancer patients and markedly lowers their quality of life. The treatment for BTCP episodes that is recommended in current guidelines involves extended-release formulations in combination with rapid-onset and short-acting opioids. In the past few years, several new preparations of fentanyl, an opioid with a very rapid onset, have been approved for this indication. Treating physicians need to be aware of the clinical differences between the newer fentanyl preparations and immediate-release opioids.

METHODS

We searched the PubMed and Embase databases for randomized controlled trials (RCTs) of fentanyl for buccal, sublingual or intranasal administration in comparison with other opioids or a different fentanyl preparation for the treatment of BTCP.

RESULTS

In 6 trials of buccal, sublingual or intranasal fentanyl versus oral immediate-release opioids for the treatment of BTCP episodes, the use of fentanyl was associated with significantly less intense pain. In particular, fentanyl more often lowered the intensity of pain by at least 33% (range between studies: 13% to 57%) or by at least 50% (range between studies: 9% to 38%) within 15 minutes. Please change to "versus" if you agree.] Dose titration should begin at the lowest dose. When one fentanyl preparation is exchanged for another, the effective dose will probably differ.

CONCLUSION

The newer fentanyl preparations extend the treatment options for BTCP. They relieve pain within a short time better than conventional, immediate-release oral opioids do and may therefore be very helpful for patients with suddenly arising, intense, and short-lasting BTCP episodes. Further comparative trials are urgently needed.

Considerations in selecting rapid-onset opioids for the management of breakthrough pain

Breakthrough pain (BTP) is a transitory pain that occurs despite the use of long-term, around-the-clock analgesia. It is highly prevalent in certain populations and places a significant burden on patients, their families, caregivers, and health-care systems. Despite its prevalence and impact, BTP is sometimes unrecognized and often undertreated. Various formulations of fentanyl – a rapid-onset opioid with short duration of action – are available for the management of BTP. The efficacy of formulations using transmucosal, transbuccal, sublingual, and intranasal administration routes has been demonstrated for BTP treatment in clinical trials. However, a lack of head-to-head trials evaluating their relative efficacy makes it challenging for physicians to reach informed decisions on the most efficacious intervention for individual patients. In the absence of clear data on the relative efficacy of fentanyl formulations, prescribing decisions need to be based on physician understanding and experience and product cost and availability, taking into account the individual patient’s needs, the ability of the patient or caregivers to administer medication, and the patient’s wishes. This review evaluates current pharmacologic methods of alleviating BTP and discusses factors that should be considered when selecting the most appropriate formulation for individual patients. With the range of fentanyl formulations available, it is now possible to successfully address BTP in the majority of patients.