Clinical pharmacokinetics of transdermal opioids: focus on transdermal fentanyl

Longitudinal evaluation of fentanyl concentrations in equine plasma and synovial fluid following application of transdermal fentanyl patches over one carpal joint

OBJECTIVE

To determine if transdermally delivered fentanyl can achieve greater concentrations of fentanyl in synovial fluid when applied over a synovial structure.

STUDY DESIGN

Randomized, experimental study.

ANIMALS

Six healthy adult horses.

METHODS

Each horse had two 100 μg/h fentanyl matrix patches applied on the dorsal aspect of one, randomly assigned, carpometacarpal joint (CMCJ) for 48 h. Whole blood and bilateral synovial samples from the intercarpal joint were obtained at 0, 2, 6, 12, 24, 36 and 48 h. Fentanyl concentrations were measured with liquid chromatography-mass spectrometry.

RESULTS

All subjects achieved detectable concentrations of fentanyl in both plasma and synovial fluid. Time to peak synovial and plasma concentration was 12 h. At 6 h, the synovial concentration in the untreated carpus (0.104 ng/mL ± 0.106) was lower than plasma fentanyl concentrations 0.31 ± 0.27 (p = .036). At 12 h, both treated (0.55 ng/mL ± 0.3) and untreated (0.53 ng/mL ± 0.28) synovial fluid fentanyl concentrations were lower than plasma (0.87 ng/mL ± 0.48) concentrations (p < .001 and p = .001, respectively). Synovial concentrations of fentanyl did not differ between treated and untreated joints (p > 0.608 for all time points).

CONCLUSION

Application of fentanyl matrix patches directly over the CMCJ did not result in increased fentanyl concentrations in the synovial fluid of the treated intercarpal joint in normal horses.

CLINICAL SIGNIFICANCE

There is likely no analgesic advantage to placing fentanyl patches directly over the affected joint, as it did not result in increased synovial concentrations at the tested site.

Advances in fentanyl testing

Fentanyl is a synthetic opioid that was approved by the FDA in the late 1960s. In the decades since, non-prescription use of fentanyl, its analogs, and structurally unrelated novel synthetic opioids (NSO) has become a worsening public health crisis. There is a clear need for accessible testing for these substances in biological specimens and in apprehended drugs. Immunoassays for fentanyl in urine are available but their performance is restricted to facilities that hold moderate complexity laboratory licenses. Immunoassays for other matrices such as oral fluid (OF), blood, and meconium have been developed but are not widely available. Point of care tests (POCT), such as lateral flow immunoassays or fentanyl test strips (FTS), are widely available but not approved by the FDA for clinical use. All immunoassays are vulnerable to false positive and false negative results. Immunoassays may or may not be able to detect fentanyl analogs and NSOs. Mass spectrometry (MS) can accurately and reliably measure fentanyl and its major metabolite norfentanyl in urine and oral fluid. MS is available at reference laboratories and large hospitals. Liquid chromatography paired with tandem mass spectrometry (LC-MS/MS) is the most widely used method and has outstanding specificity and sensitivity for fentanyl and norfentanyl. When compared to immunoassays, MS is more expensive, requires more technical skill, and takes longer to result. Newer mass spectrometry methods can measure fentanyl analogs and NSO. Both mass spectrometry assays and immunoassays [in the form of fentanyl test strips (FTS)] have potential use in harm reduction programs.

Transdermal fentanyl patch versus standard analgesia in postoperative oral submucous fibrosis patients: a triple blinded, randomised control trial

Severe pain experienced by patients with oral submucous fibrosis (OSMF) compromises their physiotherapy and negatively affects the surgical outcome and the patient's compliance. The main aim of this study was to develop a protocol for pain control in the management of OSMF postoperatively. This was a prospective, parallel with active control, double-arm, triple-blinded, randomised control trial (RCT) with 48 OSMF patients, randomised into two groups - Group A (control, n = 25): received non-opioid analgesics (NSAIDs) and Group B (cases, n = 23): received transdermal fentanyl patches (TFP). Pain and interincisal opening were measured on postoperative days 1, 3, 5, 7, 9, and 15, and on the1^st and 3^rd postoperative months. Quality of Life (QoL) was assessed preoperatively, on the 15^th day postoperatively, and 3^rd month postoperatively, and compliance was documented postoperatively on the 9^th day. The transdermal fentanyl patch was found to have statistically significantly more effect in controlling severe pain during active mouth opening exercises, and thus significantly increased the patients' compliance. Although there was increased mouth opening and QoL in the fentanyl group, the differences were statistically insignificant. Our study recommends the use of TFP for better pain control and compliance in postoperative OSMF patients.

No place for routine use of modified-release opioids in postoperative pain management

Modified-release opioid tablets were introduced into surgical practice in the belief that they provided superior pain relief and reduced nursing workload, and they rapidly became embedded into many perioperative pathways. Although national and international guidelines for the management of postoperative pain now advise against the use of modified-release opioids, they continue to be prescribed in many centres. Recognition that modified-release opioids show lack of benefit and increased risk of harm compared with immediate-release opioids in the acute, postoperative setting has become clear. Their slow onset and offset make rapid and safe titration of these opioids impossible, including down-titration as the patient recovers; pain relief may be less effective; they have been associated with an increased incidence of opioid-related adverse drug events, increased length of hospital stay, and higher readmission rates; and they lead to higher rates of opioid-induced ventilatory impairment and persistent postoperative opioid use. Evidence indicates that modified-release opioids should not be used routinely in the postoperative period.

How physical techniques improve the transdermal permeation of therapeutics: A review

BACKGROUND

Transdermal delivery is very important in pharmaceutics. However, the barrier function of the stratum corneum hinders drugs absorption. How to improve transdermal delivery efficiency is a hot topic. The key advantages of physical technologies are their wide application for the delivery of previously nonappropriate transdermal drugs, such as proteins, peptides, and hydrophilic drugs. Based on the improved permeation of drugs delivered via multiple physical techniques, many more diseases may be treated, and transdermal vaccinations become possible. However, their wider application depends on the related convenient and portable devices. Combined products comprising medicine and devices represent future commercial directions of artificial intelligence and 3D printing.

METHODS

A comprehensive search about transdermal delivery assisted by physical techniques has been carried out on Web of Science, EMBASE database, PubMed, Wanfang Database, China National Knowledge Infrastructure, and Cochrane Library. The search identified and retrieved the study describing multiple physical technologies to promote transdermal penetration.

RESULTS

Physical technologies, including microneedles, lasers, iontophoresis, sonophoresis, electroporation, magnetophoresis, and microwaves, are summarized and compared. The characteristics, mechanism, advantages and disadvantages of physical techniques are clarified. The individual or combined applicable examples of physical techniques to improve transdermal delivery are summarized.

CONCLUSION

This review will provide more useful guidance for efficient transdermal delivery. More therapeutic agents by transdermal routes become possible with the assistance of various physical techniques.

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.

Evaluation of in vitro/in vivo correlations for three fentanyl transdermal delivery systems using in vitro skin permeation testing and human pharmacokinetic studies under the influence of transient heat application

The value of developing an in vitro/in vivo correlation (IVIVC) is substantial in biopharmaceutical drug development because once the model is developed and validated, an in vitro method may be used to efficiently assess and predict drug product performance in vivo. In this study, three bioequivalent, matrix-type, fentanyl transdermal delivery systems (TDS) were evaluated in vitro using an in vitro permeation test (IVPT) and dermatomed human skin, and in vivo in human pharmacokinetic (PK) studies under harmonized study designs to evaluate IVIVC. The study designs included 1 h of transient heat application (42 ± 2 °C) at either 11 h or 18 h after TDS application to concurrently investigate the influence of heat on drug bioavailability from TDS and the feasibility of IVPT to predict the effects of heat on TDS in vivo. Level A (point-to-point) and Level C (single point) IVIVCs were evaluated by using PK-based mathematical equations and building IVIVC models between in vitro fraction of drug permeation and in vivo fraction of drug absorption. The study results showed that the three differently formulated fentanyl TDS have comparable (p > 0.05) heat effects both in vitro and in vivo. In addition, the predicted steady-state concentration (C_ss) from in vitro flux data and the observed C_ss in vivo showed no significant differences (p > 0.05). However, the effects of heat on enhancement of fentanyl bioavailability observed in vivo were found to be greater compared to those observed in vitro for all three drug products, resulting in a weak prediction of the impact of heat on bioavailability from the in vitro data. The results from the current work suggest that while IVPT can be a useful tool to evaluate the performance of fentanyl TDS in vivo with a relatively good predictability at a normal temperature condition and to compare the effect of heat on drug delivery from differently formulated TDS, additional testing measures would enhance the ability to predict the heat effects in vivo with a lower prediction error.

An Integrated Biophysical Model for Predicting the Clinical Pharmacokinetics of Transdermally Delivered Compounds

The delivery of therapeutic drugs through the skin is a promising alternative to oral or parenteral delivery routes because dermal drug delivery systems (D³S) offer unique advantages such as controlled drug release over sustained periods and a significant reduction in first-pass effects, thus reducing the required dosing frequency and level of patient noncompliance. Furthermore, D³S find applications in multiple therapeutic areas, including drug repurposing. This article presents an integrated biophysical model of dermal absorption for simulating the permeation and absorption of compounds delivered transdermally. The biophysical model is physiologically/biologically inspired and combines a holistic model of healthy skin with whole-body physiology-based pharmacokinetics through dermis microcirculation. The model also includes the effects of chemical penetration enhancers and hair follicles on transdermal transport. The model-predicted permeation and pharmacokinetics of select compounds were validated using in vivo data reported in the literature. We conjecture that the integrated model can be used to gather insights into the permeation and systemic absorption of transdermal formulations (including cosmetic products) released from novel depots and optimize delivery systems. Furthermore, the model can be adapted to diseased skin with parametrization and structural adjustments specific to skin diseases.

Case Report: Intoxication in a Pig (Sus Scrofa Domesticus) After Transdermal Fentanyl Patch Ingestion

An experimental study on the effects of electroporation on pancreatic tissue was performed in pigs, and the fentanyl transdermal patch (FTP) was used postoperatively as part of multimodal pain management. Ingestion of an FTP, which resulted in fentanyl intoxication, was suspected 5 days after placement in one of the experimental pigs. The pig was first dysphoric, running in the stall, panting and vocalizing until it finally became depressed and it remained lying on the floor. Ingestion of an FTP was not observed but the fentanyl plasma concentration on the day of intoxication was 20.7 ng/ml, while at its peak after FTP administration it was only 0.492 ng/ml. The intoxication was successfully treated with a single intramuscular naloxone injection.

Enhancement in antinociceptive and anti-inflammatory effects of tramadol by transdermal proniosome gel

Oral therapy of tramadol, an opiate analgesic, undergoes extensive hepatic metabolism and requires frequent administration. Transdermal therapy by virtue can overcome these issues and can improve the efficacy and reduce abuse liability of tramadol. The aim of this research was to investigate the possibility of transdermal delivery of tramadol by formulating proniosome gel and evaluate its therapeutic potential in vivo. The effect of formulation composition as well as amount of drug on physicochemical characteristics of prepared proniosomes were examined. Best proniosome gel (F4) was selected and evaluated for drug release, stability and transdermal efficacy by ex vivo and in vivo experiments. The vesicles demonstrated optimal properties including spherical shape, nanosize with good entrapment efficiency, adequate zeta potential, higher stability and greater transdermal flux. The amorphization and dispersion of tramadol in the aqueous core of proniosome vesicles was confirmed by differential scanning calorimeter. Release profile of F4 was distinct (P < 0.001) from control and displayed steady and prolonged tramadol release by Fickian diffusion. Transdermal therapy of F4 showed prominent reduction of induced twitches (P < 0.005) in mice and edema (P < 0.05) in rats, as compared to oral tramadol. The improvement in clinical efficacy of tramadol in transdermal therapy is correlated with the pharmacokinetic data observed. In conclusion, the observed improvement in antinociceptive and anti-inflammatory effects from proniosome carriers signifies its potential to be a suitable alternative to oral therapy of tramadol with greater efficacy.

The Role of Opioids in Pain Management in Elderly Patients with Chronic Kidney Disease: A Review Article

Chronic kidney disease (CKD) is a global public health problem. Pain is one of the most generally experienced symptoms by CKD patients. Pain management is a key clinical activity; nonetheless, insufficient pain management by health professionals keeps it up. Opioids as pain relievers are a class of naturally-derived and synthetic medications. They act through interactions with receptors in peripheral nerves. Numerous pharmacokinetic alterations happen with aging that influence drug disposition, metabolism, and quality of life. Acetaminophen alone, or combined with low-potency opioid dose is regarded as the safest pain-relieving choice for CKD. Morphine and codeine are probably eluded in renal impairment patients and used with excessive carefulness. Tramadol, oxycodone, and hydromorphone can be used by patient monitoring, while methadone, transdermal fentanyl, and buprenorphine seem to be safe to use in older non-dialysis patients with renal impairment. Consistent with the available literature, the main aim of this review was to explore the occurrence of chronic pain and its opioid treatment in CKD patients. According to this review, more and well-made randomized controlled trials are necessary to find appropriate opioid doses and explore the occurrence of side effects.

Fentanyl Plasma Concentrations after Application of a Transdermal Patch in Three Different Locations to Refine Postoperative Pain Management in Rabbits

Simple Summary

Fentanyl patches offer “stress free” postoperative pain management in rabbits. It has been shown that fentanyl uptake is dependent on exogenous and endogenous factors of the area where the patch is applied. The purpose of the study was to investigate three different locations (neck, inner and outer surface of the ear) to obtain reliable fentanyl plasma concentrations above those previously shown to be analgesic. The fentanyl plasma concentration was measured at several time points after patch application. In addition, the practicability of the proposed methods was evaluated. The group with application on the neck had the fastest uptake and equal to or over the analgesic plasma concentration for up to 72 h. The outer surface of the ear had slightly slower uptake and shorter analgesic duration whereas fentanyl uptake at the inner surface of the ear was insufficient to provide plasma analgesic concentration. The preparation of the neck proved to be the most laborious because of the thin and dense fur and the removal of the patch resulted in erythema. In conclusion, depending on how long potent analgesia is required, either the neck or the outer surface of the ear are suitable for patch application enabling “stress free” and reliable postoperative analgesia in rabbits.

Abstract

Transdermal patches allow a noninvasive and “stress free” analgesia in rabbits. As fentanyl uptake is dependent on exogenous and endogenous factors of the area where the patch is applied, this study investigated three different locations (neck, inner and outer surfaces of the ear) for fentanyl patch application to provide adequate and reliable fentanyl plasma concentrations above those previously shown to be analgesic. Fentanyl plasma concentration was measured at different time points (3, 6, 9, 12, 18, 24, 36, 48, 72, 96, 120 h) and rabbits were assessed for their general conditions and treatment-related side effects. Practicability of the proposed methods was evaluated. Following patch application on the neck, fentanyl plasma concentrations equal to or above the analgesic value were measured in all rabbits between 6 and 72 h. Comparable concentrations were reached between 9 and 48 h in all animals for the outer ear surface. However, for the inner ear surface, analgesic concentrations were not reached, even if practicability was considered the best for this location. Preparation of the neck skin was judged as the most cumbersome due to the clipping of the dense fur and patch removal resulted in erythema. In summary, the application of the fentanyl patch on the neck and outer ear surface allowed the reach of reliable plasma concentrations above the analgesic threshold in rabbits. When applied on the neck, fentanyl patches provided the longest duration of analgesic plasma concentrations, whereas patch application and removal were easier on the outer ear surface.

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.

Evaluation of Heat Effects on Fentanyl Transdermal Delivery Systems Using In Vitro Permeation and In Vitro Release Methods

Experimental conditions that could impact the evaluation of heat effects on transdermal delivery systems (TDS) using an in vitro permeation test (IVPT) and in vitro release testing (IVRT) were examined. Fentanyl was the model TDS. IVPT was performed using Franz diffusion cell, heating lamp, and human skin with seven heat application regimens. IVRT setup was similar to IVPT, without using skin. Dissolution study was conducted in a modified dissolution chamber. The activation energy of skin permeation for fentanyl was determined using aqueous solution of fentanyl. In IVPT, the increase of temperature from 32 °C to 42 °C resulted in a 2-fold increase in flux for fentanyl TDS, consistent with the activation energy determined. The magnitude of flux increase was affected by the heat exposure onset time and duration: higher flux was observed when heat was applied earlier or following sustained heat application. Heat induced flux increases could not be observed when inadequate sampling time points were used, suggesting the importance of optimizing sampling time points. Drug release from TDS evaluated using IVRT was fast and the skin was the rate-limiting barrier for TDS fentanyl delivery under elevated temperature.

Vascular Drug Delivery Using Carrier Red Blood Cells: Focus on RBC Surface Loading and Pharmacokinetics

Red blood cells (RBC) have great potential as drug delivery systems, capable of producing unprecedented changes in pharmacokinetics, pharmacodynamics, and immunogenicity. Despite this great potential and nearly 50 years of research, it is only recently that RBC-mediated drug delivery has begun to move out of the academic lab and into industrial drug development. RBC loading with drugs can be performed in several ways-either via encapsulation within the RBC or surface coupling, and either ex vivo or in vivo-depending on the intended application. In this review, we briefly summarize currently used technologies for RBC loading/coupling with an eye on how pharmacokinetics is impacted. Additionally, we provide a detailed description of key ADME (absorption, distribution, metabolism, elimination) changes that would be expected for RBC-associated drugs and address unique features of RBC pharmacokinetics. As thorough understanding of pharmacokinetics is critical in successful translation to the clinic, we expect that this review will provide a jumping off point for further investigations into this area.

Effects of a Preoperative Transdermal Fentanyl Patch on Proinflammatory Cytokine and Pain Levels During the Postoperative Period: A Randomized Controlled Trial

OBJECTIVE

The main objectives of this article were to assess the effect of preoperative transdermal fentanyl patch (TFP) on interleukin (IL)-6 and IL-8 levels and pain after laparoscopic cholecystectomy.

MATERIALS AND METHODS

Patients received a TFP (25 μg/h) (patch group, n=30) or a placebo patch (control group, n=30) applied 14 hours before operation. After surgery, control group received intravenous continuous fentanyl (25 μg/h) with loading dose (25 μg). IL-6 and IL-8 levels were measured at admission and 1, 6, 12, 24, and 48 hours postoperatively. Pain score and consumption of rescue analgesic were evaluated too.

RESULTS

At 24 hours postoperatively, IL-6 and IL-8 reached a peak and then decreased. The peak IL-6 levels were 21.92(±6.22) and 24.91(±6.81) pg/mL in the patch and control group. The significant differences of IL-6 between groups were shown at 6 and 12 hours postoperatively (P=0.032, 0.0001). There were no significant differences in IL-8 levels and pain score.

CONCLUSIONS

Preoperative TFP attenuated the increase in IL-6 levels after surgery and provided similar analgesia to continuous fentanyl infusion. Preemptive TFP may have influence on proinflammatory reactions and pain control after surgery.

Percutaneous Vertebroplasty versus Conservative Treatment Using a Transdermal Fentanyl Patch for Osteoporotic Vertebral Compression Fractures

Objective

Although surgical intervention, such as percutaneous vertebroplasty (PVP), is the standard treatment for osteoporotic vertebral compression fractures (OVCFs), its effectiveness and safety are unclear. Therefore, this study compared the safety and efficacy of conservative treatment with that of PVP for acute OVCFs.

Methods

Patients with single-level OVCFs who were treated conservatively with a transdermal fentanyl patch (TFP) or with PVP between March 2013 and December 2017 and followed-up for more than 1 year were retrospectively evaluated. Patients with pathologic fractures, fractures of more than two columns, or a history of PVP were excluded. Clinical outcomes (visual analog scale [VAS] scores) and radiographic factors were evaluated, including changes in the compression rate of the corresponding vertebral body at onset and after 12 months, sagittal Cobb angle at onset and after 6 and 12 months, and the incidence of adjacent compression fractures.

Results

Of the 131 patients evaluated, 75 were treated conservatively using TFPs and 56 underwent PVP. We divided the patients into TFP and PVP groups. Their baseline characteristics (including sex, level of fracture, and bone mineral density T-scores) were similar, but the TFP group was significantly younger. The overall VAS score for pain showed a greater decrease during the first month (1 week after PVP) in the PVP group but remained similar in the two groups thereafter. The compression rate after 12 months increased in the TFP group but decreased in the PVP group. Five patients in the PVP group, but none in the TFP group, experienced adjacent compression fractures within 12 months.

Conclusion

We compared clinical and radiological outcomes between the TFP and PVP groups. The immediate pain reduction effect was superior in the PVP group, but the final clinical outcome was similar. Although the PVP group had a better-preserved compression rate than the TFP group for 1 year, the development of adjacent fractures was significantly higher. Although TFPs seemed to be beneficial in reducing the failure rate of conservative treatment, the possibility of side effects (22.6%, 17 out of 75 patients, in this study) should be carefully monitored.

Percutaneous penetration of drugs applied in transdermal delivery systems: an in vivo based approach for evaluating computer generated penetration models

Human skin is a viable pathway for administration of therapeutics. Transdermal delivery systems (TDS) have been approved by the US-FDA since 1981. To enable the risk assessment of dermal exposure, predictive mathematical models are used. In this work the accuracy of predicted flux of the models is compared to experimental human in vivo data of drugs applied in US-FDA approved TDS. A database of pharmacokinetic data of drugs applied in TDS was used and updated. Three mathematical models (QSAR) were used to calculate predicted fluxes, and compared to the human in vivo data. For more than half of the drugs applied in TDS, the predicted flux by the mathematical models was an underestimation compared to the flux calculated with the experimental in vivo data. The flux was over- or underestimated by a factor 10-100. All mathematical models were significantly correlated with the experimental in vivo data. The process of percutaneous penetration has several influencing factors, TDS minimize some of these factors. Limitations are discussed. Further research is needed, with a focus on validation and standardization of the permeability coefficient. This work offers observations that should give a stimulus for refinement on the appropriate usage and limitations of mathematical models.

Polymorphisms associated with fentanyl pharmacokinetics, pharmacodynamics and adverse effects

Fentanyl is an agonist of the μ-opioid receptor commonly used in the treatment of moderate-severe pain. In order to study whether pharmacogenetics explains some of the variability in the response to fentanyl, several genes related to fentanyl receptors, transporters and metabolic enzymes have been analysed. Thirty-five healthy volunteers (19 men and 16 women) receiving a single 300 μg oral dose of fentanyl were genotyped for 9 polymorphisms in cytochrome P450 (CYP) enzymes (CYP3A4 and CYP3A5), ATP-binding cassette subfamily B member 1 (ABCB1), opioid receptor mu 1 (OPRM1), catechol-O-methyltransferase (COMT) and adrenoceptor beta 2 (ADRB2) by real-time PCR. Fentanyl concentrations were measured by ultra-performance liquid chromatography combined with tandem mass spectrometry (UPLC-MS/MS). Fentanyl pharmacokinetics is affected by sex. Carriers of the CYP3A4*22 allele, which is known to reduce the mRNA expression, showed higher area under the concentration-time curve (AUC) and lower clearance (Cl) values. Although this finding might be of importance, its validity needs to be confirmed in other similar settings. Furthermore, carriers of the ABCB1 C1236T T/T genotype presented a lower AUC and higher Cl, as well as lower half-life (T_1/2 ). As volunteers were blocked with naltrexone, the effect of fentanyl on pharmacodynamics might be biased; however, we could observe that fentanyl had a hypotensive effect. Moreover, ADRB2 C523A A allele carriers showed a tendency towards reducing systolic blood pressure. Likewise, OPRM1 and COMT minor allele variants were risk factors for the development of somnolence. CYP3A5*3, ABCB1 C3435T and ABCB1 G2677T/A were not associated with fentanyl's pharmacokinetics, pharmacodynamics and safety profile.

Comparative out-of-hospital mortality of long-acting opioids prescribed for non-cancer pain: A retrospective cohort study

PURPOSE

Despite significant growth of opioid prescriptions, only limited data are available regarding the comparative safety of long-acting opioids for chronic non-cancer pain. Recent data suggest that transdermal fentanyl and oxycodone CR may have greater toxicity than morphine SR in patients with non-cancer pain. Thus, we compared the risk of out-of-hospital deaths in patients with non-cancer pain filling prescriptions for transdermal fentanyl or oxycodone CR with that for morphine SR.

METHODS

We conducted a retrospective cohort study in 50 658 patients enrolled in Tennessee Medicaid who filled prescriptions for transdermal fentanyl (n = 8717), oxycodone CR (n = 14 118), or morphine SR (n = 27 823) between 1999 and 2011. We excluded individuals with cancer or other life-threatening diagnoses and used propensity scores to adjust for multiple potential confounders. The primary outcome was out-of-hospital mortality.

RESULTS

During 44 385 person-years of follow-up, 689 patients died. The out-of-hospital mortality rate among all study subjects was 155/10 000 patient-years. Contrary to earlier data suggesting greater risk, mortality was not significantly different in patients filling prescriptions for transdermal fentanyl compared with morphine SR (adjusted HR = 0.96, 95% C.I.: 0.77-1.21); moreover, patients filling prescriptions for oxycodone CR had lower mortality risk compared with those filling prescriptions for morphine SR (adjusted HR = 0.79, 95% C.I. 0.66-0.95).

CONCLUSION

In the study population, long-acting opioids for non-cancer pain were associated with high out-of-hospital mortality rates. We found comparable out-of-hospital mortality risks associated with transdermal fentanyl and morphine SR. The risk of out-of-hospital death for oxycodone CR was lower than that for morphine SR.

MAC-Sparing Effect of Transdermal Fentanyl in Sevoflurane-Anesthetized Sheep

Transdermal fentanyl allows for consistent plasma concentrations of a potent synthetic μ-opioid receptor agonist and can provide constant post-operative analgesia for up to 72 h. The aim of this study was to determine the reduction of the minimum alveolar concentration of sevoflurane (MACSEVO) by transdermal fentanyl in nonpregnant ewes. Nine sheep were mask induced with sevoflurane (SEVO in oxygen). MACSEVO determinations involved electrical current applied to the lateral metacarpus as a supramaximal stimulus and measurements in duplicate. Seven days later, a fentanyl patch (75 μg/h) was applied to each sheep and 15.1 ± 1.8 h later the MAC re-determined (MACSF). MACSF was 1.99 ± 0.32 %, corresponding to 25.6 ± 8.1 % reduction from MACSEVO (P < 0.001). Transdermal fentanyl produces a significant MACSEVO-sparing effect with minimal effect on cardiovascular parameters.

Effects of smoking and body mass index on the exposure of fentanyl in patients with cancer

The transdermal fentanyl patch is widely used to treat cancer-related pain despite its wide inter- and intrapatient variability in pharmacokinetics. The aim of this study was to investigate whether smoking and body size (i.e. body mass index) influence fentanyl exposure in patients with cancer. These are factors that typically change during treatment and disease trajectories. We performed an explorative cohort study in patients with cancer using transdermal fentanyl patches (Durogesic®), by taking a blood sample for pharmacokinetic analysis one day after applying a patch in patients with a stable fentanyl dose. A total of 88 patients were evaluable. Although no statistically significant difference was found, the plasma concentrations of non-smokers was 28% (95% CI [-14%; +89-%]) higher than those of smokers normalizing for a dose of 25μg/min. Patients with a low BMI (< 20 kg/m2) had almost similar (10% (95% CI [-39%; +97%]) higher) plasma concentrations compared to patients with a high BMI (> 25 kg/m2). A wider variation in fentanyl plasma concentrations was found in this study than anticipated. Due to this variation, studies in larger patient cohorts are needed to further investigate the effect of smoking on plasma concentration of fentanyl and thereby clarify the clinical significance of our findings.

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.

Influence of Morphine and Naloxone on Pain Modulation in Rheumatoid Arthritis, Chronic Fatigue Syndrome/Fibromyalgia, and Controls: A Double-Blind, Randomized, Placebo-Controlled, Cross-Over Study

BACKGROUND

Impaired pain inhibitory and enhanced pain facilitatory mechanisms are repeatedly reported in patients with central sensitization pain. However, the exact effects of frequently prescribed opioids on central pain modulation are still unknown.

METHODS

A randomized, double-blind, placebo-controlled cross-over trial was carried out. Ten chronic fatigue syndrome (CFS)/fibromyalgia (FM) patients, 11 rheumatoid arthritis (RA) patients and 20 controls were randomly allocated to the experimental (10 mg morphine or 0.2 mg/mL Naloxone) and placebo (2 mL Aqua) group. Pressure pain thresholds (PPTs) and temporal summation at the Trapezius and Quadriceps were assessed by algometry. Conditioned pain modulation (CPM) efficacy and deep tissue pain pressure were assessed by adding ischemic occlusion at the opposite upper arm.

RESULTS

Deep tissue pain pressure was lower and temporal summation higher in CFS/FM (P = 0.002 respectively P = 0.010) and RA patients (P = 0.011 respectively P = 0.047) compared to controls at baseline. Morphine had only a positive effect on PPTs in both patient groups (P time = 0.034). Accordingly, PPTs increased after placebo (P time = 0.015), and no effects on the other pain parameters were objectified. There were no significant effects of naloxone nor nocebo on PPT, deep tissue pain, temporal summation or CPM in the control group.

CONCLUSIONS

This study revealed anti-hyperalgesia effects of morphine in CFS/FM and RA patients. Nevertheless, these effects were comparable to placebo. Besides, neither morphine nor naloxone influenced deep tissue pain, temporal summation or CPM. Therefore, these results suggest that the opioid system is not dominant in (enhanced) bottom-up sensitization (temporal summation) or (impaired) endogenous pain inhibition (CPM) in patients with CFS/FM or RA.

The Efficacy of Fentanyl Transdermal Patch as the First-Line Medicine for the Conservative Treatment of Osteoporotic Compression Fracture

Objective

There are no strong guidelines on how long or how we should undertake conservative treatment during the acute period of an osteoporotic vertebral compression fracture (VCF).

Methods

We treated 202 patients with conservative treatment on VCF from March 2012 to August 2015. On inclusion criteria, 75 patients (22 males and 53 females) were included in the final analysis. After admission, a transdermal fentanyl patch with low dose (12.5 µg) application was attempted in all patients. In an unresponsive patient, the fentanyl patch was increased by 25 µg. After identifying the tolerable toilet ambulation of the patient without any assistance, hospital discharge was recommended. We classified two patient groups into one favorable group and one unfavorable group and compared several clinical and radiological factors.

Results

Among 75 patients, the clinical outcome of 57 patients (76%) was favorable, but that of 18 patients (24%) was unfavorable. In clinical outcomes, the numeric rating scale at 6 and 12 months and Odom's criteria at 12 months was significantly different between the favorable and the unfavorable groups. The dose of the patches used showed statistically significant differences between the two groups (p=0.001).

Conclusion

The only statistically significant affecting factor for an unfavorable outcome was the use of a higher dose fentanyl patch. Our data inferred that the unresponsiveness to a low-dose fentanyl patch could be helpful to select patients necessary for percutaneous vertebroplasty or kyphoplasty.

Comparative study of the efficacy of transdermal buprenorphine patches and prolonged-release tramadol tablets for postoperative pain control after spinal fusion surgery: a prospective, randomized controlled non-inferiority trial

PURPOSE

To compare the efficacy of a transdermal buprenorphine patch (5, 10, 15, and 20 μg/h) with that of oral tramadol (150, 200, 250, and 300 mg) for postoperative pain control after single level spinal fusion surgery.

METHODS

The present study (ClinicalTrials.gov, number NCT02416804) was a prospective, randomized controlled non-inferiority trial designed to determine the efficacy of buprenorphine TDS for alleviating postoperative pain following patient controlled analgesia (PCA) in persons underwent a single level posterior lumbar interbody fusion surgery through 1:1 allocation. The primary outcome was the Visual Analog Pain Scale (VAS) score for postoperative back pain at 7 days after surgery. The non-inferior margin of the VAS was set at δ = 1.5 points.

RESULTS

The VAS score (primary outcome) for postoperative back pain at 7 days after surgery in the Buprenorphine group was not inferior compared to the Tramadol group. The overall changes in VAS scores for postoperative pain during follow-up assessments over a 2-week period did not differ between both groups. However, the VAS scores for postoperative pain significantly improved with time after surgery in both groups. The patterns of changes in the VAS scores for postoperative pain during the follow-up period were not significantly different between the both groups.

CONCLUSIONS

The efficacy of buprenorphine TDS was not inferior to that of oral tramadol medication for alleviating postoperative pain in the subacute period from 72 h after surgery, following PCA administration. In addition, adverse events were similar between both groups.

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.

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.

Poor adhesion of fentanyl transdermal patches may mimic end-of-dosage failure after 48 hours and prompt early patch replacement in hospitalized cancer pain patients

Context

Renewal of fentanyl transdermal patch (transdermal therapeutic system [TTS]) should occur every 3 days (72 hours) according to manufacturer’s guidelines. Some studies mentioned patients reporting end-of-dose failure, and thus, some authors recommend shortening the interval of application to 2 days (48 hours). However, reasons for early replacement are mostly unknown.

Objectives

The objectives of this study were to assess the prevalence of early replacement of fentanyl TTS in a cancer center in Basel, Switzerland, and to assess the reasons for early replacement in stationary patients.

Methods

We retrieved all fentanyl TTS administered in a cancer center in Basel, Switzerland, between November 11, 2011, and January 31, 2015, from the electronic medical database.

Results

A total of 739 patients (mean age 71.4±11.5 years, 55% women) were administered 2,250 fentanyl TTS (dosage 6–500 µg/hour). Most replacements occurred after 72 hours (61.6%) and a few after 48 hours (7.4%). Patients with early replacement after 48 hours were significantly younger (63.8 years versus 71.5 years, p<0.001) and obtained higher mean dosages of fentanyl TTS (89 µg/hour versus 44.1 µg/hour, p<0.001) and rescue medication (calculated as oral morphine equivalent in milligrams: 185.1 mg versus 39.6 mg during the first 24 hours after replacement, p<0.001). No pharmacological rationale for early replacement was observed. According to 57 physicians, nurses, and pharmacists, the most often reasons for early TTS replacement were end-of-dosage pain (41.4%) and poor adhesion (31.4%).

Conclusion

In the absence of any physiological, pharmacological, or environmental reasons recorded in the database to explain an early replacement of fentanyl TTS, skin adhesion problems may point practical reasons and mimic end-of-dosage failure.

Design and functionality of a smart fentanyl iontophoretic transdermal system for the treatment of moderate-to-severe postoperative pain

Fentanyl iontophoretic transdermal system (ITS) is a patient-controlled analgesia system used for the management of acute postoperative pain. The first-generation fentanyl ITS was an integrated one-piece system; however, corrosion that could limit reliability was detected in a small number of systems. A second-generation fentanyl ITS was designed to separate the hydrogels in the Drug Unit from the electronic circuit of the Controller during manufacture and storage, removing the primary cause of corrosion and thereby improving reliability. No evidence of corrosion has been observed in over 10,000 systems tested in real-time aging studies for the second generation fentanyl ITS. The second generation fentanyl ITS design features combine to ensure safe operation of the system with high reliability.

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.

Injectable peptide hydrogels for controlled-release of opioids

Peptide-based hydrogels as a drug carrier system for the subcutaneous administration of morphine.

Perioperative Considerations in Metastatic Renal Cell Carcinoma

Patients with metastatic renal cell carcinoma are complex, with the potential for significant complications, and require extensive pre-, peri-, and postoperative management. This article discusses, in depth, the necessary considerations in the treatment of these patients.

Comparison between Transdermal Buprenorphine and Transdermal Fentanyl for Postoperative Pain Relief after Major Abdominal Surgeries

INTRODUCTION

Opioid is generally regarded as an important part of multimodal, perioperative analgesia, especially for moderate to severe pain. Amongst the various modes of delivery transdermal route has several potential benefits over oral and parentral administration. These include noninvasive dosing, better absorption and lack of first-pass metabolism. A transdermal drug delivery system provides steady and continuous drug delivery resulting in steady plasma concentration. Bolus dosing of systemic analgesic results in supra and sub therapeutic plasma resulting in toxic and sub analgesic plasma drug concentration. It also improves patient compliance.

MATERIALS AND METHODS

Sixty patients undergoing major abdominal surgery under GA were randomly divided in two groups (n=30). Group A received buprenorphine 10 mcg/h TDS and group B received 25 mcg/h fentanyl TDS, 6 hours prior to surgery. Patients were followed for three days for postoperative pain relief and adverse effects.

RESULTS

Baseline and demographic variables are comparable in both groups. The mean level of VAS was significantly lower in group B as compared to group A at Day 1, 2 and 3. The mean level of sedation score was significantly lower in Group B than Group A. Haemodynamic variables in both groups (SBP, DBP and HR), shows comparable values in both groups and no significant difference was observed. Five out of 30 (16.7%) patients in group A required single dose of rescue analgesic while 0 out of 30 patients (0.00%) in group B required rescue analgesic. This difference in rescue analgesic requirement in not quiet statistically significant (p-value 0.0522). Twenty percent patient in fentanyl group and 16.7% patients in buprenorphine group experienced some adverse effects. Nausea and vomiting were main side effects of the drugs. The incidence of nausea and vomiting were 6.7% and 10% in buprenorphine and fentanyl group respectively.

CONCLUSION

Fentanyl and buprenorphine TDS were effective and safe in controlling postoperative pain. Fentanyl is better than buprenorphine in this respect.

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.

Death by band-aid: fatal misuse of transdermal fentanyl patch

We present a case of fatal intoxication by the application of a transdermal fentanyl patch upon a superficial bleeding abrasion of a 2-year-old girl. The grandmother discovered the body of the child in bed at approximately 7 a.m. External examination revealed a properly developed, nourished, and hydrated child, with some vomit in the nostrils and inside the mouth. There was no evidence of trauma besides small contusions and abrasions on the knees, with a patch placed over the largest abrasion. Closer inspection revealed that this was transdermal fentanyl patch. Internal examination and microscopic analysis revealed regurgitation of stomach content, cerebral and pulmonary edema, and liver congestion. Toxicology analysis revealed trace levels of fentanyl in the blood just above the limit of detection (2 ng/mL), while concentrations in the urine, liver, and kidney were approximately 102, 28, and 10 ng/mL, respectively. Investigation discovered that the child injured her knee while playing the evening before. The grandmother applied the patch to cover the injury, unaware that she had used a fentanyl transdermal patch instead of simple band-aid. Although fatal intoxications are uncommon among young children in high-income countries, it is of major interest to raise awareness of such events especially since a great majority of these are preventable. The presented case points at the need for more thorough education of users and more strict rules in prescribing and handling of this potent medicine. As well, we find this case to be a useful contribution to the evaluation of postmortem fentanyl concentrations in fatal intoxication in a small child.

Pharmacokinetic study between a bilayer matrix fentalyl patch and a monolayer matrix fentanyl patch: single dose administration in healthy volunteers

Aims

Transdermal fentanyl is a well established treatment for cancer pain. The aim of the present study is to assess the relative bioavailability of fentanyl from two different transdermal systems by evaluating plasma drug concentrations after single administration of Fentalgon® (test), a novel bilayer matrix type patch, and Durogesic SMAT (reference), a monolayer matrix type patch. In the Fentalgon patch the upper 6% fentanyl reservoir layer maintains a stable concentration gradient between the lower 4% donor layer and the skin. The system provides a constant drug delivery over 72 h.

Methods

This was an open label, single centre, randomized, single dose, two period crossover clinical trial, that included 36 healthy male volunteers. The patches were applied to non-irritated and non-irradiated skin on the intraclavicular pectoral area. Blood samples were collected at different time points (from baseline to 120 h post-removal of the devices) and fentanyl concentrations were determined using a validated LC/MS/MS method. Bioequivalence was to be claimed if the 90% confidence interval of AUC(0,t) and C_max ratios (test: reference) were within the acceptance range of 80–125% and 75–133%, respectively.

Results

The 90% confidence intervals of the AUC(0,t) ratio (116.3% [109.6, 123.4%]) and C_max ratio (114.4% [105.8, 123.8%] were well included in the acceptance range and the C_max ratio also met the narrower bounds of 80–125%. There was no relevant difference in overall safety profiles of the two preparations investigated, which were adequately tolerated, as expected for opioid-naïve subjects.

Conclusions

The new bilayer matrix type patch, Fentalgon®, is bioequivalent to the monolayer matrix type Durogesic SMAT fentanyl patch with respect to the rate and extent of exposure of fentanyl (Eudra/CT no. 2005-000046-36).

Refractory cachexia is associated with increased plasma concentrations of fentanyl in cancer patients

Background

An appropriate plasma concentration of fentanyl is the key to achieving good pain control in cancer patients. Cachexia, a multifactorial syndrome, is known to affect drug-metabolizing enzymes. However, the fentanyl concentrations in the blood of patients with cachexia have not been analyzed. The aim of this study was to evaluate the influence of cancer cachexia on dose-adjusted plasma fentanyl concentrations in cancer patients.

Methods

Blood was collected from 21 Japanese cancer patients treated with a 24-hour trans-dermal fentanyl patch during the steady state of fentanyl plasma concentration. Plasma fentanyl concentrations were analyzed using liquid chromatography with tandem mass spectrometry (LC-MS/MS), and the levels were adjusted with the dose of fentanyl. Laboratory data were collected, and the cachexia stage was determined, based on study by Fearon et al. Multiple regression analysis was performed to identify the factors that affected fentanyl plasma concentrations.

Results

Eight patients were classified as precachexia, nine as cachexia, and four as refractory cachexia, and the median dose-adjusted fentanyl concentrations (ng/mL per mg/kg/day) were 27.5, 34.4, and 44.5, respectively. The dose-adjusted fentanyl concentration in patients with refractory cachexia was higher than that in patients with precachexia (Kruskal–Wallis test and post hoc Mann–Whitney U-test, P<0.01). The factors that were found to possibly affect the dose-adjusted concentration of fentanyl included aspartate aminotransferase, C-reactive protein, and estimated glomerular filtration rate, when analyzed as six independent variables (multiple regression analysis, P<0.05).

Conclusion

The dose-adjusted plasma concentrations of fentanyl increased with progression of cancer cachexia. Such an increase is associated with a multifactorial and systemic syndrome in cancer cachexia patients, including lower albumin, higher C-reactive protein, and impaired kidney function. In patients with cancer cachexia, we suggest that evaluation of cancer cachexia might help pain management when using a transdermal fentanyl patch in palliative care.

Validation of a fentanyl transdermal adhesion scoring tool for use in clinical practice

CONTEXT

The therapeutic efficacy of a transdermal system (TDS) is directly related to the adhesion of TDS, with partial adhesion resulting in lower plasma concentration. Currently there is no TDS adhesion scoring tool available for use in the clinical setting.

OBJECTIVES

To validate a U.S. Food and Drug Administration (FDA) scoring system for the adhesion of the fentanyl TDS in cancer patients.

METHODS

A library of images was created from photographs of fentanyl/placebo TDS placed on patients/volunteers. Thirty photographs, reflecting varying degrees of adhesion, were selected for each of series A and B, with 10 photographs common to both series. Each series was shown to 30 health professionals asked to score the photographs using the FDA scoring system. Validity was assessed using Spearman's rank correlation and reliability by Cohen's kappa (k). Photo editing software was used to assign control scores to each photograph.

RESULTS

Validity was high for both series (≥ 0.954). Inter-reliability (k) ranged from 0.327 to 0.858 (average, 0.547) and 0.433-0.910 (average, 0.620) in series A and B, respectively. The combined agreement across both series was 0.585. Intra-rater agreement (k) of the 10 common images was 0.605. No significant difference was observed between the scoring patterns for those with more than 10 years of working experience.

CONCLUSION

Overall, the TDS adhesion score determined by the participants visually in this study corresponded well to those generated by photo editing software, thus rendering the scoring system highly valid. The FDA scoring system is an adequate tool for assessing fentanyl TDS adhesion in clinical practice.

Life-threatening opioid toxicity from a fentanyl patch applied to eczematous skin

A 19-year-old man with a history of eczema was admitted to the emergency department following collapsing at home. The paramedics found him unresponsive with poor respiratory effort and a widespread erythematous rash. Anaphylaxis, thought to be secondary to flucloxacillin he had recently been prescribed, was diagnosed. Epinephrine, steroids and antihistamines were administered without clinical improvement. On arrival to hospital, constricted pupils were noted prompting the emergency physicians to consider opiate toxicity. Intravenous naloxone brought about an immediate recovery. His father subsequently disclosed that he had given his son one of his own fentanyl patches to alleviate the distressing symptoms of eczema. Although the patient had removed the patch prior to collapsing, he had suffered life-threatening opioid toxicity likely due to enhanced opiate absorption through eczematous skin. This case highlights the risks associated with fentanyl patches in patients with chronic skin conditions.

Prodrug strategies for enhancing the percutaneous absorption of drugs

The transdermal application of drugs has attracted increasing interest over the last decade or so, due to the advantages it offers, compared to other delivery methods. The development of an efficient means of transdermal delivery can increase drug concentrations, while reducing their systemic distribution, thereby avoiding certain limitations of oral administration. The efficient barrier function of the skin, however, limits the use of most drugs as transdermal agents. This limitation has led to the development of various strategies to enhance drug-skin permeation, including the use of penetration enhancers. This method unfortunately has certain proven disadvantages, such as the increased absorption of unwanted components, besides the drug, which may induce skin damage and irritancy. The prodrug approach to increase the skin’s permeability to drugs represents a very promising alternative to penetration enhancers. The concept involves the chemical modification of a drug into a bioreversible entity that changes both its pharmaceutical and pharmacokinetic characteristics to enhance its delivery through the skin. In this review; we report on the in vitro attempts and successes over the last decade by using the prodrug strategy for the percutaneous delivery of pharmacological molecules.