Transdermal fentanyl: an updated review of its pharmacological properties and therapeutic efficacy in chronic cancer pain control

Developing a machine learning-based predictive model for the analgesic effectiveness of transdermal fentanyl in cancer patients: an interpretable approach

BACKGROUND

Cancer-related pain is a common and distressing symptom in patients with malignant tumors, significantly affecting quality of life. Transdermal fentanyl is a convenient opioid option for patients with intestinal obstruction or difficulty swallowing; however, some patients do not experience adequate pain relief. Predicting transdermal fentanyl analgesic effectiveness is crucial to optimize pain management.

AIM

This study aimed to develop a predictive model for transdermal fentanyl effectiveness in cancer patients.

METHOD

Clinical data from adult cancer pain patients at Chongqing University Cancer Hospital were analyzed (January 2020-December 2022). Logistic regression and feature selection were applied, followed by developing nine predictive models using Logistic Regression, Random Forest (RF), and Extreme Gradient Boosting. The receiver operating characteristic (ROC) curves, the Youden index, and the Brier score were used to evaluate the performance of the model. Cross-validation and SHapley Additive exPlanations (SHAP) analysis were used for validation and feature interpretation.

RESULTS

Among 151 patients, 27.2% reported ineffectiveness of transdermal fentanyl. Logistic regression identified key factors of NRS, transdermal fentanyl dosage, BMI, and ALT. Among the nine models, RF Model 8 exhibited the best performance, achieving a ROC-AUC of 0.984 (95% CI: [0.968, 0.999]). This performance was further validated by the confusion matrix metrics and visualization results. The SHAP analysis highlighted BMI, lower doses, NRS, and ALT as predictors of transdermal fentanyl ineffectiveness.

CONCLUSION

The Random Forest model offers a valuable tool for predicting the effectiveness of transdermal fentanyl in cancer pain patients, supporting the refined assessment and management of pain.

Transdermal fentanyl induced paralytic intestinal obstruction in advanced liver cancer: a case report

Introduction

Transdermal fentanyl (TDF) is a commonly used analgesic drug for managing moderate-to-severe chronic cancer pain. Similar to those observed during the administration of other opioid agonists, the most frequently observed adverse drug reactions during TDF administration include nausea, vomiting, and constipation. However, there have been no reports of TDF causing intestinal obstruction yet. We report a case of TDF-induced paralytic intestinal obstruction confirmed by clinical presentations and imaging findings.

Case presentation

We administered TDF (4.2 mg once every 72 h) for external use to a patient who was admitted with acute upper gastrointestinal bleeding, suffering from advanced liver cancer, and having previously received irregular analgesia. Despite achieving satisfactory analgesic effects, he developed nausea, vomiting, constipation, reduced anal exhaust, and absence of bowel sounds on the fifth day of TDF administration. An X-ray test revealed the presence of flatulence and signs of air fluid levels in the intestine. Conventional treatment was ineffective, and paralytic intestinal obstruction was finally alleviated only after TDF was substituted with oral morphine.

Conclusion

Our findings indicate that, even when TDF is administered in conventional doses, there is a risk of inducing rare cases of intestinal obstruction. In the event of such an occurrence, adjusting the analgesic treatment plan should be the utmost priority.

Nitrosyl factors play a vital role in the ventilatory depressant effects of fentanyl in freely moving guinea pigs

An understanding of intracellular mechanisms by which fentanyl and other synthetic opioids exert adverse effects on breathing is needed. Using freely moving adult male guinea pigs, we administered the nitric oxide synthase (NOS) inhibitor, L-NAME (NG-nitro-L-arginine methyl ester), to determine whether nitrosyl factors, such as nitric oxide and S-nitrosothiols, play a role in fentanyl-induced respiratory depression. Ventilatory parameters were recorded by whole body plethysmography to determine the effects of fentanyl (75 μg/kg, IV) in guinea pigs that had received a prior injection of vehicle (saline), L-NAME or the inactive D-isomer, D-NAME (both at 50 μmol/kg, IV), 15 min beforehand. L- and D-NAME elicited minor effects on most parameters, including frequency of breathing, tidal volume and minute ventilation, although L-NAME did decrease end expiratory pause and non-eupneic breathing index (NEBI). Subsequent injection of fentanyl in guinea pigs pre-treated with vehicle produced profound and sustained reductions in frequency, tidal volume, minute ventilation, peak inspiratory flow, and inspiratory and expiratory drives, while increasing inspiratory time, expiratory time, end inspiratory pause, and NEBI. These ventilatory depressant effects of fentanyl seen in guinea pigs pre-treated with vehicle were markedly diminished in guinea pigs pre-treated with L-NAME. Moreover, the adverse effects of fentanyl on many recorded breathing parameters were converted to stimulatory effects. In contrast, D-NAME did not alter any of the effects of fentanyl on breathing. This study is the first to characterize the role nitrosyl factors play in the intracellular mechanisms involved in fentanyl-induced respiratory depression in guinea pigs.

The pharmacokinetics and pharmacodynamics of fentanyl administered via transdermal patch in horses

Introduction

Understanding the pharmacokinetics and pharmacodynamics of fentanyl in horses is crucial for optimizing pain management strategies in veterinary medicine.

Methods

Six adult horses were enrolled in a randomized crossover design. Treatments included: placebo, two 100 mcg/h patches (LDF), four 100 mcg/h patches (MDF), and six 100 mcg/h patches (HDF). Patches were in place for 72 h. Blood was obtained for fentanyl plasma concentration determination, thermal threshold, mechanical threshold, heart rate, respiratory rate, and rectal temperature were obtained prior patch placement and at multiple time points following patch placement for the following 96 h. Fentanyl plasma concentration was determined using LC-MS/MS. Data were analyzed using a generalized mixed effects model.

Results

Mean (range) maximum plasma concentration (Cmax), time to Cmax, and area under the curve extrapolated to infinity were 1.39 (0.82-1.82), 2.64 (1.21-4.42), 4.11 (2.78-7.12) ng/ml, 12.7 (8.0-16.0), 12.7 (8.0-16.0), 12 (8.0-16.0) h, 42.37 (27.59-55.56), 77.24 (45.62-115.06), 120.34 (100.66-150.55) h ng/ml for LDF, MDF, and HDF, respectively. There was no significant effect of treatment or time on thermal threshold, mechanical threshold, respiratory rate, or temperature (p > 0.063). There was no significant effect of treatment on heart rate (p = 0.364). There was a significant effect of time (p = 0.003) on heart rate with overall heart rates being less than baseline at 64 h.

Conclusions

Fentanyl administered via transdermal patch is well absorbed and well tolerated but does not result in an anti-nociceptive effect as measured by thermal and mechanical threshold at the doses studied.

Abuse potential of fentanyl and fentanyl analogues

Introduction

In this perspective review, we evaluated the clinical management of fatal fentanyl overdose in several routes of administration, concentrating on both legally prescribed and illegally produced formulations.

Methods

A literature search was conducted on Web of Science, PubMed, and Google Scholar databases, using the following keywords: fentanyl, illicit fentanyl, deaths, misuse, abuse, and naloxone. We included only articles whose abstracts were available in English. All articles were screened using their abstracts to determine their relevance to the current review.

Results

The gold standard for treating both acute and chronic pain is fentanyl, but abuse of the drug has exploded globally since the late 2000s. Fentanyl abuse has been shown to frequently result in serious harm and even death.

Conclusion

By educating patients and physicians, making rescue kits easily accessible, developing vaccines to prevent opioid addiction, and perhaps even creating new tamper-resistant fentanyl formulations, it may be possible to prevent fentanyl misuse, therapeutic errors, and the repercussions that follow.

Improving postoperative analgesia in hallux valgus surgery: oral opioids suppression by addition of a single transdermal fentanyl patch: a prospective evaluation

The last decade there is an exponential increase in opioid related deaths. This is proven to be correlated with the rising medical prescription rates of strong opioids. We investigated whether pain after hallux valgus surgery under popliteal nerve block could be adequately controlled without the prescription of oral opioids, with a single transdermal fentanyl patch. In this prospective observational study with 100 patients undergoing corrective first metatarsal osteotomies we prospectively investigated the adverse effects and need for extra pain medication. The transdermal fentanyl patch was applied one hour before surgery, prior to the ultrasound guided popliteal nerve block. Patients filled out a questionnaire every 6 hours to evaluate the pain [VAS-score], nausea [PONV-score], activity [acivity and ambulation score] and the intake of extra medication. Postoperative pain was well controlled [Mean VAS 2,53]. The maximum mean VAS score [3.93] was recorded 36 hours postoperatively. 63.8% of patients had less pain than expected. No major adverse effects were reported by the patients. Nausea was mainly mild and the majority of patients reported 'no effect' or 'sometimes' effect on daily activities. In an era where surgeons need to be aware of the threat of overuse of strong opioids, the use of a single transdermal fentanyl patch in combination with an ultrasound guided nerve block can be a good alternative in hallux valgus surgery. The use of the patch seems to obviate the need for oral opioids after discharge. Nausea and vomiting were a concern - as expected -, but only at 24 and 36 hours. On the other hand nausea did not seem to affect activity, as there was a gradual increase in activity score over time.

Predicting transdermal fentanyl delivery using physics-based simulations for tailored therapy based on the age

Transdermal fentanyl patches are an effective alternative to the sustained release of oral morphine for chronic pain management. Due to the narrow therapeutic range of fentanyl, the concentration of fentanyl in the blood needs to be carefully monitored. Only then can effective pain relief be achieved while avoiding adverse effects such as respiratory depression. This study developed a physics-based digital twin of a patient by implementing drug uptake, pharmacokinetics, and pharmacodynamics models. The twin was employed to predict the in-silico effect of conventional fentanyl transdermal in a 20–80-year-old virtual patient. The results show that, with increasing age, the maximum transdermal fentanyl flux and maximum concentration of fentanyl in the blood decreased by 11.4% and 7.0%, respectively. However, the results also show that as the patient's age increases, the pain relief increases by 45.2%. Furthermore, the digital twin was used to propose a tailored therapy based on the patient's age. This predesigned therapy customized the duration of applying the commercialized fentanyl patches. According to this therapy, a 20-year-old patient needs to change the patch 2.1 times more frequently than conventional therapy, which leads to 30% more pain relief and 315% more time without pain. In addition, the digital twin was updated by the patient's pain intensity feedback. Such therapy increased the patient's breathing rate while providing effective pain relief, so a safer treatment. We quantified the added value of a patient's physics-based digital twin and sketched the future roadmap for implementing such twin-assisted treatment into the clinics.

Opioid-induced adrenal insufficiency in transdermal fentanyl treatment: a revisited diagnosis in clinical setting

Opioids are widely used for treatment of acute and chronic pain. However, opioids have several well-known clinical adverse effects such as constipation, nausea, respiratory depression and drowsiness. Endocrine dysfunctions are also opioid-induced adverse effects but remain under-diagnosed in clinical settings, especially opioid-induced adrenal insufficiency (OIAI). A 46-year-old woman was treated with transdermal fentanyl at a dose of 90-120 mg daily morphine milligram equivalent for non-malignant chronic pain for four years. Fatigue, loss of appetite and decrease in vitality began about two years after starting fentanyl. Subsequently, constipation and abdominal pain appeared and became worse, which led to suspicion of adrenal insufficiency. Clinical diagnosis of OIAI was established based on laboratory findings of secondary adrenal insufficiency, including corticotropin-releasing hormone stimulation test, clinical history of long-term fentanyl use, and exclusion of other hypothalamic-pituitary diseases. Oral corticosteroid replacement therapy was unable to relieve her abdominal pain and constipation; opioid-rotation and dose-reduction of fentanyl were not feasible because of her persistent pain and severe anxiety. While her clinical course clearly suggested that long-term, relatively high-dose transdermal fentanyl treatment may have contributed to the development of secondary adrenal insufficiency, the symptoms associated with OIAI are generally non-specific and complex. Together with under-recognition of OIAI as a clinical entity, the non-specific, wide range of symptoms can impede prompt diagnosis. Thus, vigilance for early symptoms enabling treatments including corticosteroid replacement therapy is necessary for patients taking long-term and/or high dose opioid treatment.

Nitrosyl factors play a vital role in the ventilatory depressant effects of fentanyl in unanesthetized rats

There is an urgent need to understand the intracellular mechanisms by which synthetic opioids, such as fentanyl, depress breathing. We used L-NAME (N^G-nitro-L-arginine methyl ester), a nitric oxide synthase (NOS) inhibitor, to provide evidence for a role of nitric oxide (NO) and nitrosyl factors, including S-nitrosothiols, in fentanyl-induced suppression of breathing in rats. We measured breathing parameters using unrestrained plethysmography to record the changes produced by bolus administration of fentanyl (25 μg/kg, IV) in male Sprague Dawley rats that were pretreated with vehicle (saline), L-NAME (50 μmol/kg, IV) or the inactive D-isomer, D-NAME (50 μmol/kg, IV), 15 min previously. L-NAME produced a series of ventilatory changes that included (i) sustained elevations in breathing frequency, due to the reductions in the durations of inspiration and expiration, (ii) sustained elevations in minute ventilation, accompanied by minimal changes in tidal volume, and (iii) increases in inspiratory drive and expiratory drive, and peak inspiratory flow and peak expiratory flow. Subsequent administration of fentanyl in rats pretreated with vehicle produced negative effects on breathing, including decreases in frequency, tidal volume and therefore minute ventilation. Fentanyl elicited markedly different responses in rats that were pretreated with L-NAME, and conclusively, the negative effects of fentanyl were augmented by the NOS inhibitor. D-NAME did not alter ventilatory parameters or modulate the effects of fentanyl on breathing. Our study fully characterized the effects of L-NAME on ventilation in rats and is the first to suggest a potential role of nitrosyl factors in the ventilatory responses to fentanyl. Our data shows that nitrosyl factors reduce the expression of fentanyl-induced changes in ventilation.

Current management of cancer pain in Italy: Expert opinion paper

Introduction

Chronic pain and breakthrough cancer pain (BTcP) have a high prevalence in all cancer types and cancer stages, combined with a significant physical, psychological, and economic burden. Despite efforts to improve appropriate management of cancer pain, a poor assessment and guilty undertreatment are still reported in many countries. The purpose of this expert opinion paper is to contribute to reduce and clarify these issues with a multidisciplinary perspective in order to share virtuous paths of care.

Methods

Common questions about cancer pain assessment and treatment were submitted to a multidisciplinary pool of Italian clinicians and the results were subsequently discussed and compared with the findings of the published literature.

Conclusion

Despite a dedicated law in Italy and effective treatments available, a low percentage of specialists assess pain and BTcP, defining the intensity with validated tools. Moreover, in accordance with the findings of the literature in many countries, the undertreatment of cancer pain is still prevalent. A multidisciplinary approach, more training programs for clinicians, personalised therapy drug formulations, and virtuous care pathways will be essential to improve cancer pain management.

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.

Opioid Receptors and Protonation-Coupled Binding of Opioid Drugs

Opioid receptors are G-protein-coupled receptors (GPCRs) part of cell signaling paths of direct interest to treat pain. Pain may associate with inflamed tissue characterized by acidic pH. The potentially low pH at tissue targeted by opioid drugs in pain management could impact drug binding to the opioid receptor, because opioid drugs typically have a protonated amino group that contributes to receptor binding, and the functioning of GPCRs may involve protonation change. In this review, we discuss the relationship between structure, function, and dynamics of opioid receptors from the perspective of the usefulness of computational studies to evaluate protonation-coupled opioid-receptor interactions.

Case report on postmortem fentanyl measurement after overdose with more than 67 fentanyl patches

Purpose

Fentanyl is an analgesic that is frequently prescribed, which resulted in non-intentional as well as intentional misuse and deaths. Here, we present a postmortem case of a patient who clearly died of a fentanyl overdose due to an extensive number of fentanyl patches combined with oral intake of fentanyl and cocaine. We aimed to show how postmortem analysis can be used to interpret postmortem fentanyl concentrations in unique cases like the one we present.

Case description

A 23-year-old male was found dead in his bedroom with 67 non-prescribed patches of fentanyl on his body. In the room, there also were fentanyl tablets of 100 µg and cocaine powder, which had possibly also been taken by the deceased. To confirm the cause of death, urine and subclavian blood were retrieved to perform a standard postmortem toxicology screening. The toxicological screening revealed the presence of several drugs, including cocaine, fentanyl, lidocaine and paracetamol. Further analysis of the quantitative postmortem values of fentanyl with ultra-performance liquid chromatography-tandem mass spectrometry revealed a fentanyl concentration of 57.9 µg/L. Considering several issues around postmortem drug analyses, this value seemed to be in line with concentrations found in previously reported postmortem cases.

Conclusion

We were able to confirm the expected cause of death with an extensive toxicological screening in combination with the circumstantial evidence. We identified fentanyl as most important cause for the fatal outcome in this specific case and simultaneously contributed to the limited availability of knowledge on postmortem fentanyl concentrations.

Fentanyl use disorder characterized by unprescribed use of transdermal patches: a case report

BACKGROUND

Fentanyl is a synthetic opioid with analgesic potency 75-100 times higher than that of morphine, and its analgesic effect is used for pain treatment, mostly in cancer patients. Using fentanyl patches may reduce misuse potential due to the transdermal route of administration, long-acting action, sustained release delivery property, and maintenance of steady-state serum concentration of the drug. Although there have been reports of transdermal fentanyl patches (TFPs) misuse via transmucosal, trans-nasal, intravenous, and oral routes of administration, fentanyl use disorder via the transdermal route is very rare.

CASE

In this case report, we present a patient with a history of substance use disorder who developed fentanyl use disorder via transdermal route after using unprescribed TFP in order to quit opium gum. The CARE guidance was followed in the preparation of this case report.

CONCLUSION

The risk of use disorder may be higher, especially in individuals with a history of substance use disorders. This risk should be taken into account when clinicians prescribe this medication.

CHARMM Force-Field Parameters for Morphine, Heroin, and Oliceridine, and Conformational Dynamics of Opioid Drugs

Opioid drug binding to specialized G protein-coupled receptors (GPCRs) can lead to analgesia upon activation via downstream G_i protein signaling and to severe side effects via activation of the β-arrestin signaling pathway. Knowledge of how different opioid drugs interact with receptors is essential, as it can inform and guide the design of safer therapeutics. We performed quantum and classical mechanical computations to explore the potential energy landscape of four opioid drugs: morphine and its derivatives heroin and fentanyl and for the unrelated oliceridine. From potential energy profiles for bond twists and from interactions between opioids and water, we derived a set of force-field parameters that allow a good description of structural properties and intermolecular interactions of the opioids. Potential of mean force profiles computed from molecular dynamics simulations indicate that fentanyl and oliceridine have complex energy landscapes with relatively small energy penalties, suggesting that interactions with the receptor could select different binding poses of the drugs.

Pain Management in Breast Cancer Patients: A Multidisciplinary Approach

Pain is a significant problem and is one of the most invalidating symptoms in breast cancer (BC) patients that would negatively affect the functional status and the Quality of Life (QoL). Pain management in BC patients requires thorough patient evaluation and critical assessment of pain. The actual cause for the pain must be recognized, so management can be tailored to each patient. This review aims to discuss various treatment modalities employed for effectively managing pain in BC patients.

Pharmacotherapy makes up the cornerstone of the management of pain in BC patients. Both opioid and non-opioid analgesics are utilized. The WHO recommends a method called “by the ladder” for managing pain in BC patients where analgesics are used in ascending order. In comprehensive pain management (CPM), non-pharmacologic therapies are gaining wide acceptance and popularity, including complementary and alternative medicine (CAM), procedural and psychosocial interventions. Procedural interventions are usually used in case of severe pain refractory to pharmacological therapy. Techniques, such as radiotherapy, neurectomy, and nerve blocks, are effective in managing cancer pain. However, CAM therapies in BC pain management need to be guided by enough scientific evidence, decision-making, and medical judgment of regulatory bodies.

BC pain management is based on careful routine pain assessments and appropriate patient evaluation both physically and psychologically. Pain control is one of the methods to improve the QoL of BC patients. Both pharmacological and non-pharmacological therapies are accessible to patients today, but they should be used with caution to minimize toxicity and increase effectiveness. The use of any pain management intervention should be based on proper scientific evidence and collective medical judgment.

Inverse Mechanistic Modeling of Transdermal Drug Delivery for Fast Identification of Optimal Model Parameters

Transdermal drug delivery systems are a key technology to administer drugs with a high first-pass effect in a non-invasive and controlled way. Physics-based modeling and simulation are on their way to become a cornerstone in the engineering of these healthcare devices since it provides a unique complementarity to experimental data and additional insights. Simulations enable to virtually probe the drug transport inside the skin at each point in time and space. However, the tedious experimental or numerical determination of material properties currently forms a bottleneck in the modeling workflow. We show that multiparameter inverse modeling to determine the drug diffusion and partition coefficients is a fast and reliable alternative. We demonstrate this strategy for transdermal delivery of fentanyl. We found that inverse modeling reduced the normalized root mean square deviation of the measured drug uptake flux from 26 to 9%, when compared to the experimental measurement of all skin properties. We found that this improved agreement with experiments was only possible if the diffusion in the reservoir holding the drug was smaller than the experimentally measured diffusion coefficients suggested. For indirect inverse modeling, which systematically explores the entire parametric space, 30,000 simulations were required. By relying on direct inverse modeling, we reduced the number of simulations to be performed to only 300, so a factor 100 difference. The modeling approach's added value is that it can be calibrated once in-silico for all model parameters simultaneously by solely relying on a single measurement of the drug uptake flux evolution over time. We showed that this calibrated model could accurately be used to simulate transdermal patches with other drug doses. We showed that inverse modeling is a fast way to build up an accurate mechanistic model for drug delivery. This strategy opens the door to clinically ready therapy that is tailored to patients.

Expert consensus of the Chinese Association for the Study of Pain on pain treatment with the transdermal patch

Chronic pain lasting more than 3 mo, or even several years can lead to disability. Treating chronic pain safely and effectively is a critical challenge faced by clinicians. Because administration of analgesics through oral, intravenous or intramuscular routes is not satisfactory, research toward percutaneous delivery has gained interest. The transdermal patch is one such percutaneous delivery system that can deliver drugs through the skin and capillaries at a certain rate to achieve a systemic or local therapeutic effect in the affected area. It has many advantages including ease of administration and hepatic first pass metabolism avoidance as well as controlling drug delivery, which reduces the dose frequency and side effects. If not required, then the patch can be removed from the skin immediately. The scopolamine patch was the first transdermal patch to be approved for the treatment of motion sickness by the Food and Drug Administration in 1979. From then on, the transdermal patch has been widely used to treat many diseases. To date, no guidelines or consensus are available on the use of analgesic drugs through transdermal delivery. The pain branch of the Chinese Medical Association, after meeting and discussing with experts and based on clinical evidence, developed a consensus for promoting and regulating standard use of transdermal patches containing analgesic drugs.

The pharmacokinetics of a fentanyl matrix patch applied at three different anatomical locations in horses

BACKGROUND

Matrix fentanyl patches have not been investigated in horses and may represent an effective means of providing analgesia over an extended time period without venous catheterisation.

OBJECTIVES

To describe the pharmacokinetics of a matrix transdermal fentanyl patch in horses.

STUDY DESIGN

Randomised experiment, Latin-square design.

METHODS

Six adult horses were given each of three treatments with a 96-hour washout. For each treatment, two 100 µg/h matrix fentanyl patches were applied to the inguinal region (TXA), metacarpus (TXM) or ventral tail base (TXT) for 72 hours. Blood samples for fentanyl analysis were obtained and heart rate (HR), respiratory rate (RR) and rectal temperature (RT) were measured at various time points for 96 hours. Fentanyl plasma concentrations were measured with LC-MS/MS for pharmacokinetic analysis. A mixed-effects model was used to analyse pharmacodynamic variables.

RESULTS

The time to maximum plasma concentration, maximum plasma concentration and area under the curve extrapolated to infinity were 10 ± 3.79, 14.3 ± 5.13 and 10.3 ± 4.8 hours; 2.07 ± 0.74, 1.55 ± 0.53 and 2.07 ± 0.72 ng/mL; and 46.6 ± 9.3, 44.6 ± 6.0 and 46.2 ± 7.68 ng hours/mL for TXA, TXM and TXT respectively. There was no significant difference among groups. There was no significant change from baseline or among treatment groups with regard to HR, RR or RT (P > .1 for all).

MAIN LIMITATIONS

There was no intravenous treatment group for determination of bioavailability.

CONCLUSIONS

Fentanyl was rapidly absorbed and persisted in the plasma for up to 96 hours. No adverse effects of treatment on HR, RR or RT were observed. Further controlled prospective studies are needed to determine what plasma concentration, if any, of fentanyl achieves an analgesic effect in horses when administered via a transdermal patch system.

Opioid transdermal delivery system: a useful method for pain management in children

Transdermal delivery system (TDDS) is a non-invasive and less expensive method for drug delivery. Despite its feasibility, only a restricted group of drugs can be delivered by TDDS, because of the little permeability of skin. Moreover, TDDS is limited to lipophilic drugs with small molecular masses and it is not indicated for peptides, macromolecules and hydrophilic drugs. Among opioids, fentanyl and buprenorphine are suitable for transdermal administration only for chronic pain management (not for acute pain). However, opioid TDDS still remains off-label for chronic pain management in children. In this review, we describe the main features of the adhesive TDDS and the main characteristics of pediatric skin and the differences from the adult one. Moreover, we focus on fentanyl and buprenorphine patches and their non-invasive mechanism of action, and on the main aspects that make them suitable for pain management among the pediatric population.

Predicting Transdermal Fentanyl Delivery Using Mechanistic Simulations for Tailored Therapy

Transdermal drug delivery is a key technology for administering drugs. However, most devices are “one-size-fits-all”, even though drug diffusion through the skin varies significantly from person-to-person. For next-generation devices, personalization for optimal drug release would benefit from an augmented insight into the drug release and percutaneous uptake kinetics. Our objective was to quantify the changes in transdermal fentanyl uptake with regards to the patient’s age and the anatomical location where the patch was placed. We also explored to which extent the drug flux from the patch could be altered by miniaturizing the contact surface area of the patch reservoir with the skin. To this end, we used validated mechanistic modeling of fentanyl diffusion, storage, and partitioning in the epidermis to quantify drug release from the patch and the uptake within the skin. A superior spatiotemporal resolution compared to experimental methods enabled in-silico identification of peak concentrations and fluxes, and the amount of stored drug and bioavailability. The patients’ drug uptake showed a 36% difference between different anatomical locations after 72 h, but there was a strong interpatient variability. With aging, the drug uptake from the transdermal patch became slower and less potent. A 70-year-old patient received 26% less drug over the 72-h application period, compared to an 18-year-old patient. Additionally, a novel concept of using micron-sized drug reservoirs was explored in silico. These reservoirs induced a much higher local flux (µg cm^-2 h^-1) than conventional patches. Up to a 200-fold increase in the drug flux was obtained from these small reservoirs. This effect was mainly caused by transverse diffusion in the stratum corneum, which is not relevant for much larger conventional patches. These micron-sized drug reservoirs open new ways to individualize reservoir design and thus transdermal therapy. Such computer-aided engineering tools also have great potential for in-silico design and precise control of drug delivery systems. Here, the validated mechanistic models can serve as a key building block for developing digital twins for transdermal drug delivery systems.

Changes in Percutaneous Absorption of Fentanyl Patches in Rats Treated with a Sebum-Like Secretion

The percutaneous absorption of a fentanyl (FEN)-patch is affected by various external factors including the volume of sebum secretion, which causes changes in the skin surface environment. In this study, we prepared a lard-based sebum-like secretion (SLS), and applied it to investigate the effect of different skin surface conditions on the drug penetration of a FEN-patch. In vitro work to test drug release using the Franz diffusion cell indicated that drug release was significantly suppressed by treatment with 5% SLS, which is equivalent to the amount of daily human sebum secretion. Conversely, in ex vivo experiments using rat skin, the amount of FEN that accumulated in the skin tissue of the 5% SLS-treated rats was higher in comparison with the non-SLS treated group. Furthermore, in vivo experiments indicated that the plasma FEN concentration in rats treated with the FEN-patch was significantly increased by treatment with 5% SLS. These results suggest that the sebum affected the release, accumulation, and absorption of FEN from the FEN-patch, and the FEN concentration in the blood was reflected by the balance of the suppression of drug release and the enhancement of drug accumulation in the skin with SLS.

Death in Sauna Associated With a Transdermal Fentanyl Patch

We present a case of an accidental fatal fentanyl overdose caused by increased uptake of the drug from a transdermal patch while experiencing the heat of a sauna.The transdermal patch administers fentanyl at a relatively constant rate through the skin. However, in the subcutaneous tissue, blood circulation greatly influences the rate of this drug's systemic intake. In the present case, an elderly woman with multiple health conditions was prescribed fentanyl patches but was unaware of the risks associated with external heat sources when one wears the patch. She was found dead in the sauna with a postmortem femoral blood concentration of fentanyl that was elevated (15 μg/L). The cause of death was determined to be fatal poisoning by fentanyl with the contributing factor of external heat from the sauna.Risks associated with transdermal administration of a potent opioid-like fentanyl are widely described in the scientific literature and described in the manufacturer's summary of product characteristics. Physicians and pharmacists should take particular care to ensure that patients understand these risks.

Consensus Perioperative Management Best Practices for Patients on Transdermal Fentanyl Patches Undergoing Surgery

PURPOSE OF REVIEW

The administration of a transdermal fentanyl patch can be complicated with different pharmacokinetics than other fentanyl preparations.

RECENT FINDINGS

The medical condition and baseline opioid requirements must all be carefully considered when dosing a fentanyl patch. An advantage of the fentanyl patch is its ability to bypass the gastrointestinal tract and in many patients, provide effective analgesia with minimal side effects. Fentanyl patches must be carefully administered since morbidity and/or mortality can result from the following: Giving higher doses than a patient needs, combining the medication with potent sedatives, or heating a fentanyl patch. The use of a transdermal fentanyl patch for the treatment of acute postoperative pain is not recommended and any patient undergoing a surgical procedure should have the fentanyl patch removed preoperatively. The current manuscript discusses the history of fentanyl and the fentanyl patch, as well as perioperative considerations, contraindications, current clinical efficacy, and clinical adversities related to the transdermal fentanyl patch. Regarding the heating of a transdermal fentanyl patch, which significantly increases blood levels of fentanyl, it is of the utmost importance that the patch be removed prior to surgery.

An Interdisciplinary Approach to Reducing Opioid Prescriptions to Patients with Chronic Pain in a Spinal Cord Injury Center

BACKGROUND

The increasing use of prescription opioids has contributed to the epidemic of opioid abuse in the United States. Efforts to reduce opioid prescriptions and offer alternatives for pain management are needed.

OBJECTIVE

To determine the success of a multidisciplinary project to manage chronic pain while reducing reliance on opioids in a population of patients with spinal cord injury (SCI).

DESIGN

Retrospective analysis.

SETTING

This study was conducted in an SCI system of care in northeast Ohio.

PARTICIPANTS

Individuals with SCI receiving outpatient care were included.

INTERVENTIONS

Clinicians in SCI and pain management specialties developed a plan to manage individuals with SCI, particularly for individuals using opioids, including physical, occupational, recreational, and vocational therapy. These services worked closely with the SCI physicians when chronic pain was identified to help better medically manage their pathology and support efforts to decrease opioid use in a multipronged approach.

MAIN OUTCOMES

The primary outcome measures from opioid prescription data from 2008 to 2016 were the percent of outpatients receiving opioids, opioid prescription rates, and opioid prescription doses over time.

RESULTS

The percentage of outpatients receiving opioids and the number of opioid prescriptions through the outpatient service significantly decreased, from 39% to 16% and from 2.5 to 1.5 prescriptions per patient per quarter, respectively, correlating with the introduction of the multidisciplinary interventions. The total morphine equivalent quantities of prescription medications, particularly nonmethadone opioids, also decreased significantly.

CONCLUSIONS

The multidisciplinary interventional approach was associated with marked decreases in the percentage of patients receiving opioids and the amounts of opioids being prescribed. This reduction could have a significant impact on the opioid crisis.

LEVEL OF EVIDENCE

IV.

Influence of aprepitant and localization of the patch on fentanyl exposure in patients with cancer using transdermal fentanyl

Background and Objectives

The cutaneous fentanyl patch is widely used to treat continuous pain in patients with cancer. Its use is hampered by a high inter- and intrapatient pharmacokinetic variability. Factors that influence this pharmacokinetic variability are largely unclear. The aim of these studies was to test if common patient variables, i) the use of the moderate CYP3A4 inhibitor aprepitant and ii) the localization of the fentanyl patch (upper arm versus thorax) influence systemic exposure to fentanyl in patients with cancer using a transdermal fentanyl patch.

Results

The AUC_{0-6 h} of fentanyl was 7.1% (95% CI: -28% to +19%) lower if patients concurrently used aprepitant, compared to the period when patients used fentanyl only. The AUC_{0-4 h} of fentanyl was 7.4% (95% CI: -22% to +49%) higher when the cutaneous fentanyl patch was applied to the upper arm compared to application at the thorax.

Conclusions

Neither the concurrent use of aprepitant, nor the localization of the fentanyl patch showed a statistically significant influence on fentanyl pharmacokinetics.

Methods

We performed two prospective cross-over pharmacokinetic intervention studies. Both studies had two eight-day study periods. At day 8 of each study period blood samples were collected for pharmacokinetic analysis. In each study 14 evaluable patients were included.

Antinociceptive and respiratory effects following application of transdermal fentanyl patches and assessment of brain μ-opioid receptor mRNA expression in ball pythons

OBJECTIVE To quantify plasma fentanyl concentrations (PFCs) and evaluate antinociceptive and respiratory effects following application of transdermal fentanyl patches (TFPs) and assess cerebrospinal μ-opioid receptor mRNA expression in ball pythons (compared with findings in turtles). ANIMALS 44 ball pythons (Python regius) and 10 turtles (Trachemys scripta elegans). PROCEDURES To administer 3 or 12 μg of fentanyl/h, a quarter or whole TFP (TFP-3 and TFP-12, respectively) was used. At intervals after TFP-12 application in snakes, PFCs were measured by reverse-phase high-pressure liquid chromatography. Infrared heat stimuli were applied to the rostroventral surface of snakes to determine thermal withdrawal latencies after treatments with no TFP (control [n = 16]) and TFP-3 (8) or TFP-12 (9). Breathing frequency was measured in unrestrained controls and TFP-12-treated snakes. μ-Opioid receptor mRNA expression in brain and spinal cord tissue samples from snakes and turtles (which are responsive to μ-opioid receptor agonist drugs) were quantified with a reverse transcription PCR assay. RESULTS Mean PFCs were 79, 238, and 111 ng/mL at 6, 24, and 48 hours after TFP-12 application, respectively. At 3 to 48 hours after TFP-3 or TFP-12 application, thermal withdrawal latencies did not differ from pretreatment values or control treatment findings. For TFP-12-treated snakes, mean breathing frequency significantly decreased from the pretreatment value by 23% and 41% at the 24- and 48-hour time points, respectively. Brain and spinal cord tissue μ-opioid receptor mRNA expressions in snakes and turtles did not differ. CONCLUSIONS AND CLINICAL RELEVANCE In ball pythons, TFP-12 application resulted in high PFCs, but there was no change in thermal antinociception, indicating resistance to μ-opioid-dependent antinociception in this species.

Addressing the barriers related with opioid therapy for management of chronic pain in India

India has a high prevalence of chronic disorders which may be associated with persistent pain. Despite the availability of multiple treatment options, chronic pain is largely untreated and contributes to disability and mortality. Medical consumption of opioids remains low due to various barriers that prevent access to opioids for patients and healthcare practitioners. Stringent regulatory provisions outlined in the Narcotic Drugs and Psychotropic Substances Act (1985) have been major deterrents to adequate opioid use. Although multiple amendments to the act have ensured ease of opioid access for medicinal purposes, concerns such as lack of awareness and prescribing practices and attitudes of physicians/patients still need to be addressed. This review aims to identify these barriers and suggest recommendations to overcome them.

Head and Neck Cancer Pain

Pain is a significant morbidity resulting from head and neck cancer. Pain may also be the result of the treatments directed against head and neck cancer. An experienced practitioner may manage this pain by understanding the multifactorial mechanisms of pain and the various pharmacotherapies available. Pain should be managed with multiple medications in a multimodal approach, and nonpharmacologic therapies should be considered as well.

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.

Synthesis and biological evaluation of fentanyl acrylic derivatives

Synthesis and biological evaluation of fentanyl acrylic derivatives.

Clinical Usefulness of Long-term Application of Fentanyl Matrix in Chronic Non-Cancer Pain: Improvement of Pain and Physical and Emotional Functions

BACKGROUND

Opioids are recently recommended for those who do not gain adequate pain relief from the use of acetaminophen or nonsteroidal anti-inflammatory drugs. Medical opioids are administered in various routes, and transdermal opioid products that can make up for the weaknesses of the oral or intravenous products have been developed. This study is to evaluate the clinical usefulness of fentanyl matrix in terms of the long-term improvement in pain and physical and mental functions.

METHODS

This was a multicenter, open, prospective, observational study that was conducted in 54 institutions in Korea. Patients with non-cancerous chronic pain completed questionnaires, and investigators also completed questionnaires. A total of 1,355 subjects participated in this study, and 639 subjects completed the study. Subjects received transdermal fentanyl matrix (12 µg/hr, 25 µg/hr, or 50 µg/hr depending on the patient's response and demand). Subjects visited at 29 ± 7 days, 85 ± 14 days, and 169 ± 14 days after administration, respectively, to receive drug titration and fill out the questionnaires. The results were analyzed using the intention-to-treat (ITT) analysis, full analysis set (FAS), and per-protocol (PP) analysis. The FAS analysis included only 451 participants; the PP analysis, 160 participants; and the ITT analysis, 1,355 participants.

RESULTS

The intensity of pain measured by the Numeric Rating Scale decreased from 7.07 ± 1.78 to 4.93 ± 2.42. The physical assessment score and mental assessment score of the Short-Form Health Survey 12 improved from 28.94 ± 7.23 to 35.90 ± 10.25 and from 35.80 ± 11.76 to 42.52 ± 10.58, respectively. These differences were significant, and all the other indicators also showed improvement. Adverse events with an incidence of ≥ 1% were nausea, dizziness, vomiting, and pruritus.

CONCLUSIONS

The long-term administration of fentanyl matrix in patients with non-cancerous pain can reduce the intensity of pain and significantly improves activities of daily living and physical and mental capabilities.

Are newer, more expensive pharmacotherapy options associated with superior symptom control compared to less costly agents used in a collaborative practice setting?

Innovative approaches to care may be necessary to provide the most effective symptom management to hospice patients. One approach is prescribing newer pharmacotherapy options with the potential to improve symptom management in hospice. Such therapies are sometimes prescribed outside of Food and Drug Administration indications and are typically more costly than older agents usedfor the same symptoms. Another approach is the collaborative practice (CP) care model, whereby clinical pharmacists are given prescriptive authority according to evidence-based protocols and algorithms within boundaries approved by a physician. The agents typically included in CPprotocols are those with wide therapeutic indices and with substantial evidence to support their use. The purpose of this study was to examine both approaches to management ofpain, insomnia, and nausea, comparing symptom scores for those patients who received noncollaborative drug therapies (transdermal fentanyl, zolpidem, and ondansetron) to those who received agents under CP (oral sustained-release opioids, temazepam, andprochlorperazine). The object of the study was to investigate outcomes associated with newer drug therapy options as compared to older agents for the management of pain, insomnia, and nausea. A secondary goal is to compare symptom outcomes for patients receiving pharmaceutical care under CP and non-CP models. The study design was retrospective with a cohort. A total of 50 patients were randomly selected for each cohort of the pain and insomnia study arms. Only 45 patients prescribed oral ondansetron met inclusion criteriafor the nausea group; 45 patients prescribed prochlorperazine were randomly selected as the comparator group. Patients were compared on their degree of response to the prescribed therapy. Response was classified as complete, partial, no improvement from baseline, worsened, or unknown. A complete response was defined as the symptom score improving to a 0 of 10, regardless of the previous value documented. A partial response was defined as any improvement in score that did not result in a 0 of 10. No improvement from baseline reflected a lack of overall change in score throughout the series of data points collected. A worsened response was any score found to be higher than the score documented at the time of dispense. The unknown category reflects any set of scores that had an “NIA” documented at the time of medication dispense or when documented for both attempts subsequent to dispensing the medication. A complete response was present in 14 of 50 (24 percent) of the patients prescribed fentanyl as compared with 12 of 50 (28 percent) of those prescribed oral therapy (p = .82). Responses defined as partial, no improvement over baseline, worsened, and unknown were also comparable between the two cohorts. A complete response was seen in 26 patients prescribed temazepam (52 percent), whereas only 11 (22 percent) of patients initially prescribed zolpidem achieved the same response (p = .003 7). Both groups had a similar distribution of partial, no improvement over baseline, and worsened responses. For the nausea arm of the study, a difference was found in the number of complete responses, favoring prochlorperazine (22 of 45, 48.9 percent for prochlorperazine, 12 of 45, 26.7 percent for ondansetron, p =. 0504), as well as an increased number of worse responses seen with ondansetron patients (p = .0513); however, neither difference was statistically significant. Newer pharmacotherapy options for the management of pain, insomnia, and nausea were not found to be superior when compared to older agents prescribed under CR

[Good clinical practice guide for opioids in pain management: the three Ts - titration (trial), tweaking (tailoring), transition (tapering)]

BACKGROUND AND OBJECTIVES

Achieving good clinical practice in the use of opioids as part of a comprehensive pain management regimen can face significant challenges. Despite guidelines from governmental and pain society/organization sources, there are still significant hurdles. A review of some basic tenets of opioid analgesia based on current published knowledge and experiences about this important healthcare imperative is warranted.

CONTENT

Consistent with guidelines, the literature supports using the lowest total opioid dose that provides adequate pain control with the fewest adverse effects. Titration (or trial) during opioid initiation is a way of starting low and going slow (and assessing the appropriateness of a specific opioid and formulation). Recognizing that multiple factors contribute to an individual's personal experience of pain, the physical, psychological, social, cultural, spiritual, pharmacogenomic, and behavioral factors of the individual patient should be taken into account (tweaking, or tailoring). Finally, for those patients for whom transition (tapering) from opioid is desired, doing so too rapidly can have negative consequences and minimization of problems during this step can be achieved by proper tapering.

CONCLUSION

We conclude that a simultaneously aggressive, yet conservative, approach is advocated in the literature in which opioid therapy is divided into three key steps (the 3 T's): titration (or trial), tweaking (or tailoring), and transition (or tapering). Establishment of the 3 T's along with the application of other appropriate good medical practice and clinical experience/judgment, including non-pharmacologic approaches, can assist healthcare providers in the effort to achieve optimal management of pain.

Treatment with subcutaneous and transdermal fentanyl: results from a population pharmacokinetic study in cancer patients

Purpose

Transdermal fentanyl is effective for the treatment of moderate to severe cancer-related pain but is unsuitable for fast titration. In this setting, continuous subcutaneous fentanyl may be used. As data on the pharmacokinetics of continuous subcutaneous fentanyl are lacking, we studied the pharmacokinetics of subcutaneous and transdermal fentanyl. Furthermore, we evaluated rotations from the subcutaneous to the transdermal route.

Methods

Fifty-two patients treated with subcutaneous and/or transdermal fentanyl for moderate to severe cancer-related pain participated. A population pharmacokinetic model was developed and evaluated using non-linear mixed-effects modelling. For rotations from subcutaneous to transdermal fentanyl, a 1:1 dose conversion ratio was used while the subcutaneous infusion was continued for 12 h (with a 50 % tapering after 6 h). A 6-h scheme with 50 % tapering after 3 h was simulated using the final model.

Results

A one-compartment model with first-order elimination and separate first-order absorption processes for each route adequately described the data. The estimated apparent clearance of fentanyl was 49.6 L/h; the absorption rate constant for subcutaneous and transdermal fentanyl was 0.0358 and 0.0135 h⁻¹, respectively. Moderate to large inter-individual and inter-occasion variability was found. Around rotation from subcutaneous to transdermal fentanyl, measured and simulated plasma fentanyl concentrations rose and increasing side effects were observed.

Conclusions

We describe the pharmacokinetics of subcutaneous and transdermal fentanyl in one patient cohort and report several findings that are relevant for clinical practice. Further research is warranted to study the optimal scheme for rotations from the subcutaneous to the transdermal route.

Electronic supplementary material

The online version of this article (doi:10.1007/s00228-015-2005-x) contains supplementary material, which is available to authorized users.