Comparison of equivalent doses of fentanyl buccal tablets and arteriovenous differences in fentanyl pharmacokinetics

Population pharmacokinetic model of subcutaneous fentanyl in older acute care patients

PURPOSE

Subcutaneous fentanyl injection is commonly prescribed to manage acute pain in older patients; however, there is a gap in the literature describing the pharmacokinetic parameters for this route of administration in this population. The aim of this study was to develop and evaluate a population pharmacokinetic model for subcutaneous fentanyl injection in older patients.

METHODS

Twenty-one patients who received subcutaneous fentanyl injections (50 to 75 μg) were recruited. Fentanyl concentrations were determined using a validated liquid chromatography/tandem mass spectrometry method. A population pharmacokinetic model was developed using non-linear mixed-effects modelling. A base model was selected based on the Akaike information criterion. Age, sex, body weight, number of previous fentanyl doses, number of prescribed medications, creatinine clearance, Charlson Comorbidity Index, Identification of Seniors at Risk score and concurrent use of CYP3A4 inhibitors were covariates considered for inclusion. A p value of < 0.05 was considered statistically significant for inclusion of covariates in the final model by stepwise addition. The simulation performance of the model was assessed by visual predictive check.

RESULTS

A one-compartment, first-order absorption with lag time and linear elimination model was the best to fit to the fentanyl concentration data. The absorption rate constant was 0.136 h^-1 (between subject variability (BSV), 46%), lag time 0.66 h (BSV 51%), apparent volume of distribution 6.28 L (BSV 30%), and apparent clearance 16.3 L.h^-1 (BSV 54%). The Charlson Comorbidity Index was the only covariate included in the final model, where a higher value of the index increased fentanyl exposure and C_max.

CONCLUSION

This is the first report of subcutaneous fentanyl population pharmacokinetic model to evaluate fentanyl pharmacokinetic in older patients. The between subject variability in clearance and subcutaneous absorption rate was relatively high, and some patients recorded high fentanyl concentrations in the context of their titration to effect.

Sampling Site Has a Critical Impact on Physiologically Based Pharmacokinetic Modeling

It has been shown that arterial (central) and venous (peripheral) plasma drug concentrations can be very different. While pharmacokinetic studies typically measure drug concentrations from the peripheral vein such as the arm vein, physiologically based pharmacokinetic (PBPK) models generally output simulated concentrations from the central venous compartment that physiologically represents the right atrium, a merge of the superior and inferior vena cava. In this study, a physiologically based peripheral forearm sampling site model was developed and verified using nicotine, ketamine, lidocaine, and fentanyl as model drugs. This verified model allows output of simulated peripheral venous concentrations that can be meaningfully compared with observed pharmacokinetic data from the arm vein. The generalized effect of PBPK model sampling site on simulation output was investigated. Drugs and metabolites with large volumes of distribution showed considerable concentration discrepancy between the simulated central venous compartment and the peripheral arm vein after intravenous or oral administration, resulting in significant differences in values for C _max and time taken to reach C _max (t _max ) In addition, the simulated central venous metabolite profile showed an unexpected profile that was not observed in the peripheral arm vein. Using fentanyl as a model compound, we show that using the wrong sampling site in PBPK models can lead to biased model evaluation and subsequent erroneous model parameter optimization. Such an error in model parameters along with the discrepant sampling site could dramatically mislead the pharmacokinetic prediction in unstudied clinical scenarios, affecting the assessment of drug safety and efficacy. Overall, this study shows that PBPK model publications should specify the model sampling sites and match them with those employed in clinical studies. SIGNIFICANCE STATEMENT: Our study shows that sampling from the central venous compartment (right atrium) during physiologically based pharmacokinetic model development gives rise to biased model evaluation and erroneous model parameterization when observed data are collected from the peripheral arm vein. This can lead to a clinically significant error in predictions of plasma concentration-time profiles in unstudied scenarios. To address this error, we developed and verified a novel peripheral sampling site model to simulate arm vein drug concentrations that can be applied to different drug dosing scenarios.

Fundamentals of Pharmacokinetics to Assess the Correlation Between Plasma Drug Concentrations and Different Blood Sampling Methods

PURPOSE

Various blood collection methods were developed and used in the pharmacokinetic evaluation of drugs. However, the influence of different blood sampling methods on plasma drug concentrations has not been clarified. In the present study, we aimed to determine whether the plasma concentration of a target drug changes based on the collection site and elucidate the mechanism responsible for this change.

METHODS

We compared three blood sampling methods commonly used in small animals. Eight clinical drugs were selected and administered to rats simultaneously via intracardiac injection or oral gavage. Blood samples were collected from different sites at the same individual, and pharmacokinetic properties of the drugs were then evaluated.

RESULTS

Study results showed that the maximum plasma concentration or area under the curve of three study drugs was significantly higher in rats when blood was sampled from the carotid artery than when it was sampled from the caudal vein or by tail snip.

CONCLUSIONS

Pharmacokinetics of certain drugs may differ based on the blood sampling site. The acid-base properties of drugs may influence pharmacokinetic evaluation. The rate and extent of drug distribution may also cause such differences and have significant effects on plasma drug levels.

Assessment and treatment of breakthrough cancer pain: from theory to clinical practice

Breakthrough cancer pain (BTcP) is a common condition in oncological patients. However, its management is still suboptimal. Improved knowledge of BTcP and its management in clinical practice may have immediate importance for all physicians involved in the supportive care of cancer patients. This review critically discusses the most important concepts for the correct diagnosis of BTcP and presents some intriguing cases of the management of this condition in clinical practice. Overall, the most appropriate therapeutic choice appears to be a rapid-onset opioid (ROO), and in particular, the nasal route of administration is the quickest and most convenient mode of administration for the management of BTcP, especially when the patient needs rapid resolution of pain. To this end, intranasal fentanyl spray may have a particular relevance in clinical practice. Future research should focus on accepted definitions of BTcP to investigate the optimal management of this highly heterogeneous pain condition. Therapeutic decision-making of patients, clinicians, and payers will likely be driven from results of well-designed clinical trials of ROOs.

Rapid acting fentanyl formulations in breakthrough pain in cancer. Drug selection by means of the System of Objectified Judgement Analysis

Drug selection of rapid acting fentanyl formulations in the treatment of breakthrough pain in patients with cancer is performed by the System of Objectified Judgement Analysis method. All seven available formulations were included in the analysis. The following selection criteria were used: number of available strengths, variability in the rate of absorption, interactions, clinical efficacy, side effects, ease of administration and documentation. No direct double-blind comparative studies between two or more formulations were identified and the clinical documentation of all formulations is limited. The most distinguishing criterion was ease of use. This led to slightly higher scores for Abstral, Instanyl and PecFent than for the other formulations. The pros and cons of each formulation should be discussed with the patient, and the most suitable formulation selected for each individual patient.

Breakthrough cancer pain (BTcP): a synthesis of taxonomy, pathogenesis, therapy, and good clinical practice in adult patients in Italy

Pain presents in 80% of patients with advanced cancer, and 30% have periods of increased pain due to fluctuating intensity, known as breakthrough cancer pain (BTcP). BTcP is high-intensity, short-duration pain occurring in several episodes per day and is non-responsive to treatment. The clinical approach to BTcP is variable. A review of the literature was performed to provide clinicians and practitioners with a rational synthesis of the ongoing scientific debate on BTcP and to provide a basis for optimal clinical approach to BTcP in adult Italian patients. Data show that circadian exacerbations of pain should be carefully monitored, differentiating, if possible, between fluctuations of background pain (BP), end-of-dose effect, and BTcP. BTcP should be monitored in all care contexts in clinical practice and each care facility must have all the medications and products approved for use in BTcP at their disposal. Data show that knowledge about medications for BTcP is lacking: medications for BTcP treatment are not interchangeable, although containing the same active substance; each physician must know the specific characteristics of each medication, its pharmacological properties, limitations in clinical practice, specifics relating to titration and repeatability of administration, and technical specifics relating to the accessibility and delivery. Importantly, before choosing a rapid-onset opioid (ROO), it is essential to deeply understand the status of patient and the characteristics of their family unit/caregivers, taking into account the patient’s progressive loss of autonomy and/or cognitive-relational functionality. When BTcP therapy is initiated or changed, special attention must be paid to training the patient and family members/caregivers, providing clear instructions regarding the timing of drug administration. The patient must already be treated effectively with opioids before introducing ROOs for control of BTcP.

Clinical pharmacology of fentanyl buccal tablet for the treatment of breakthrough pain

Fentanyl buccal tablet (FBT) is a new formulation of fentanyl providing rapid-onset analgesia for the treatment of breakthrough pain. FBT has been approved for the management of breakthrough pain in patients with cancer who are already receiving and who are tolerant to opioid therapy for underlying persistent pain. FBT has demonstrated a favorable pharmacokinetic profile, which is closely aligned to the rapid onset and duration of an episode of breakthrough pain, and is generally safe and well tolerated.

Pharmacokinetics of non-intravenous formulations of fentanyl

Fentanyl was structurally designed by Paul Janssen in the early 1960s as a potent opioid analgesic (100-fold more potent than morphine). It is a full agonist at μ-opioid receptors and possesses physicochemical properties, in particular a high lipophilicity (octanol:water partition coefficient >700), which allow it to cross quickly between plasma and central nervous target sites (transfer half-life of 4.7-6.6 min). It undergoes first-pass metabolism via cytochrome P450 3A (bioavailability ~30 % after rapid swallowing), which can be circumvented by non-intravenous formulations (bioavailability 50-90 % for oral transmucosal or intranasal formulations). Non-intravenous preparations deliver fentanyl orally-transmucosally, intranasally or transdermally. Passive transdermal patches release fentanyl at a constant zero-order rate for 2-3 days, making them suitable for chronic pain management, as are iontophoretic transdermal systems. Oral transmucosal and intranasal routes provide fast delivery (time to reach maximum fentanyl plasma concentrations 20 min [range 20-180 min] and 12 min [range 12-21 min], respectively) suitable for rapid onset of analgesia in acute pain conditions with time to onset of analgesia of 5 or 2 min, respectively. Intranasal formulations partly bypass the blood-brain barrier and deliver a fraction of the dose directly to relevant brain target sites, providing ultra-fast analgesia for breakthrough pain. Thanks to the development of non-intravenous pharmaceutical formulations, fentanyl has become one of the most successful opioid analgesics, and can be regarded as an example of a successful reformulation strategy of an existing drug based on pharmacokinetic research and pharmaceutical technology. This development broadened the indications for fentanyl beyond the initial restriction to intra- or perioperative clinical uses. The clinical utility of fentanyl could be expanded further by more comprehensive mathematical characterizations of its parametric pharmacokinetic input functions as a basis for the rational selection of fentanyl formulations for individualized pain therapy.

A review of the pharmacokinetic profile of transmucosal fentanyl formulations

BACKGROUND AND OBJECTIVES

Breakthrough pain (BTP) is a transitory flare of moderate-to-severe pain that occurs in patients with stable, controlled persistent pain. Management of BTP episodes is difficult because frequency, time-to-peak intensity, and duration of episodes vary both within and between individuals. Formulations of fentanyl that use a buccal, sublingual, or nasal transmucosal route of administration have been developed for the treatment of BTP in opioid-tolerant patients with cancer. These formulations allow rapid passage into the bloodstream and avoid first-pass metabolism and, therefore, are more likely to match the time-course of BTP episodes than are oral formulations. The purposes of this analysis were to identify and review published data describing the pharmacokinetic properties of rapid-onset fentanyl formulations and to evaluate these properties in view of the temporal dynamic characteristics of BTP in order to help guide medical practice.

METHODS

Relevant publications were searched in the PubMed database from 1998. The plasma drug concentration-time profile of each formulation obtained from the identified studies was adjusted to a consistent scale for comparison.

RESULTS

The data revealed that the various transmucosal formulations resulted in three typical plasma fentanyl concentration profiles: (1) type 1: a very rapid rise and short duration; (2) type 2: a rapid increase and sustained intensity; and (3) type 3: a slower onset and longer duration.

CONCLUSIONS

Given the substantial variability of BTP episodes experienced by patients, these pharmacokinetic differences may provide useful information for a physician who is selecting a rapid-onset opioid medication for a patient.

Inhaled fentanyl aerosol in healthy volunteers: pharmacokinetics and pharmacodynamics

BACKGROUND

Rapid delivery of potent opioid to the systemic circulation is an important feature for the effective treatment of acute and acute-on-chronic breakthrough pain. The delivery of different opioids by the pulmonary route has been inconsistent, usually resulting in low bioavailability of the drug. Staccato® Fentanyl for Inhalation is a handheld inhaler producing a single metered dose of aerosolized fentanyl during a single inspiration. The aerosol is of high purity (≥98%) at a particle size (1 to 3.5 microns) shown to be best for pulmonary absorption.

METHODS

We conducted the study in healthy volunteers in 2 stages. In the crossover stage, 10 subjects received IV fentanyl 25 µg and inhaled fentanyl 25 µg on separate occasions. The dose escalation stage was a multidose, randomized, double-blind, placebo-controlled, single-period dose escalation study of inhaled fentanyl (50 to 300 µg). Serial blood sampling was performed over an 8-hour period after drug administration to determine the pharmacokinetic profile, and serial pupillometry was performed as a measure of pharmacodynamic effect.

RESULTS

In the crossover stage the pharmacokinetic profiles of the inhaled and IV fentanyl showed similar peak arterial concentrations and areas under the curve. The time to maximum concentration was slightly shorter for the inhaled than IV fentanyl, 20.5 and 31.5 seconds, respectively. In the dose escalation stage the administration of repeated doses resulted in predictable, dose-dependent serum concentrations.

CONCLUSIONS

This study has demonstrated that the pharmacokinetic profile of single doses of inhaled fentanyl is comparable to IV administration.

Fentanyl (transmucosal)

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A comprehensive review of rapid-onset opioids for breakthrough pain

Breakthrough pain (BTP) is a transitory pain (reaching maximum severity in ~15 minutes and lasting ~60 minutes in patients with cancer) that occurs despite the management of chronic pain with long-term around-the-clock analgesia. BTP occurs in 33-65% of patients with chronic cancer pain and in ~70% of patients with chronic noncancer pain. BTP has historically been managed with short-acting opioids; however, these medications have a pharmacokinetic profile that does not correlate with the sudden onset and short time to maximum severity of BTP. Interest in rapid-onset opioids to relieve BTP has therefore been growing. This comprehensive review aims to summarize the currently available clinical data for the approved rapid-onset opioids, which comprise different formulations of fentanyl, a μ-opioid receptor agonist with anaesthetic and analgesic properties. Administration routes for fentanyl in the management of BTP currently include the transmucosal and intranasal routes; an intrapulmonary formulation is also in development. The findings of this review suggest that the efficacy and safety of the approved rapid-onset opioids are comparable.

Breakthrough pain in patients referred to pain clinics: the Italian pain network retrospective study

INTRODUCTION

Despite breakthrough pain (BTP) being one of the most severe forms of pain, there are no definitive data on its prevalence.

METHODS

The authors performed a retrospective survey of the prevalence of BTP in consecutive patients in four Italian pain clinics, subsequent to application of an Italian law mandating detailed clinical records on pain characteristics, treatment, and results. Mean pain intensity was assessed with a numerical rating scale from 0 to 10.

RESULTS

The authors analyzed records of 1,401 patients (58% women, 33.1% patients with cancer). Transient episodes of severe pain or BTP were referred by 790 patients (56.4%), including 58.2% of the men (342 of 588) and 55.1% of the women (448 of 813). Among the 464 patients with cancer, 70.3% reported daily exacerbation of pain. The mean BTP intensity was 8.31 ± 1.58 and 31.1% of patients reported experiencing three episodes per day.

CONCLUSION

Despite some limitations of the study, the authors show that transient episodes of severe pain or BTP are significantly present both in cancer and other diseases, and that many patients are not yet receiving appropriate opioid therapy. The authors need validated tools at international level for the diagnosis and treatment of BTP in patients with cancer and for transitory and patients with severe non-cancer pain. A survey at national level is needed to estimate the prevalence of BTP in different settings, to plan specific medical education.

Pharmacokinetics of fentanyl buccal tablet: a pooled analysis and review

Fentanyl buccal tablet (FBT) is indicated for the treatment of breakthrough pain in patients who are already receiving and are tolerant to opioid therapy for underlying, persistent cancer pain. FBT is designed to enhance the rate and efficiency of absorption of fentanyl through the buccal mucosa. FBT was shown to be dose proportional from 100 to 1,300 μg. This analysis provides an overview of the pharmacokinetic profile of FBT based on pooled data from nine pharmacokinetic studies. In all, 365 healthy non-opioid-tolerant adults receiving naltrexone were included in the analysis. Single-dose (100 to 1,300 μg) pharmacokinetic parameters were dose normalized to 100 μg. Pharmacokinetic measures included maximum observed plasma drug concentration (C(max)), plasma drug concentration versus time curve from time zero to infinity (AUC(0-∞)), time to reach C(max) (T(max)), apparent plasma terminal elimination rate constant, and elimination half-life. After FBT administration, fentanyl was rapidly absorbed, with T(max) ranging from 20 minutes to 4 hours postdose. Mean AUC(0-∞) was 1.49 ng•hour/mL, and mean C(max) was 0.237 ng/mL. However, plasma fentanyl concentration reached 80% of C(max) within 25 minutes and was maintained through 2 hours after administration. Based on the individual studies, bioequivalence was shown for sublingual and buccal tablet placement, and no significant effect of dwell time (duration of FBT presence in the oral cavity) was observed. The pharmacokinetic profile of FBT was characterized by rapid absorption, which is consistent with the rapid-onset efficacy profile of FBT observed in clinical studies.

Single-dose pharmacokinetics of fentanyl buccal soluble film

Objective

The objectives of the study were to determine the absolute bioavailability of fentanyl from fentanyl buccal soluble film, estimate the percentage of a fentanyl dose absorbed through the buccal mucosa, and compare the bioavailability of equivalent doses administered either as single or multiple dose units.

Design

Open-label, randomized, four-period, Latin-square crossover pharmacokinetic study.

Setting

Inpatient phase 1 unit.

Patients

Twelve healthy volunteers.

Interventions

Injectable fentanyl citrate (200 µg) administered by intravenous infusion, injectable fentanyl citrate (800 µg/16 mL) administered orally, and fentanyl buccal soluble film (800 µg) administered as a single film and as four separate 200 µg films simultaneously.

Outcome Measures

Plasma concentrations after fentanyl dosing; pharmacokinetic parameters.

Results

The two buccal film treatments were bioequivalent and both had an absolute bioavailability of 71%. The percentage of an administered dose absorbed through the buccal mucosa was calculated to be 51%.

Conclusions

Fentanyl buccal soluble film effectively delivers a high percentage of the administered fentanyl dose and nearly identical plasma profiles are obtained when equivalent doses are delivered by single or multiple dosage units.

Formulations of fentanyl for the management of pain

Fentanyl is an opioid initially developed for parenteral administration. While oral administration is not an option due to a high first-pass metabolism, its high potency and lipophilicity have made a number of new routes of administration feasible. The transdermal therapeutic system offers an excellent option for long-term treatment of cancer and chronic pain, achieving stable plasma concentrations over the treatment period. The recent change from reservoir to matrix systems has made these systems more convenient to wear and safer to use, while being bioequivalent. In contrast, the patient-controlled iontophoretic transdermal system has been developed to enable on-demand delivery of transdermal bolus doses of fentanyl to treat postoperative pain. It offers a needle-free system to provide patient-controlled analgesia otherwise offered by intravenous pumps. However, due to technical difficulties the system is currently not clinically available. Oral transmucosal fentanyl utilizes the rapid uptake through the buccal mucosa to achieve high plasma concentrations rapidly and is indicated to treat breakthrough pain in patients who are not opioid-naive. The recently introduced fentanyl buccal tablets offer slightly better pharmacokinetics for the same indication. The intranasal route is another option to achieve rapid uptake of fentanyl, and is currently being investigated to provide acute and breakthrough pain relief. Transpulmonary administration of fentanyl remains experimental and this route of administration is not yet in clinical use. Overall, the specific pharmacological and physicochemical properties of fentanyl have made this compound highly suitable for novel routes of administration in a range of clinical indications.

A new transmucosal drug delivery system for patients with breakthrough cancer pain: the fentanyl effervescent buccal tablet

Breakthrough pain, a transitory severe pain with the background of otherwise controlled persistent pain has a prevalence between 52% and 67% in outpatients with cancer. Medications for such sudden-onset pain require non-invasive delivery of a potent and short-acting opioid for rapid pain relief. Although oral transmucosal delivery of fentanyl citrate (OTFC) has been shown to provide better pain relief than a typical oral opioid administration such as morphine sulfate immediate release (MSIR) in the management of breakthrough pain in patients with cancer-related pain, newer delivery systems offer a potential for further enhancement of pain relief. The fentanyl effervescent buccal tablet (FBT) formulation employs a novel drug delivery system that relies on an effervescence reaction to improve buccal fentanyl absorption. Using the effervescence reaction results in the production and dissipation of carbon dioxide with a dynamic shift in pH as the tablet dissolves. The induced low pH favors dissolution of fentanyl citrate in saliva (higher water solubility). The subsequent increase in pH thereafter favors the buccal absorption of non-ionized fentanyl across the buccal mucosa. Such a pH “pumping” mechanism increases the permeation of fentanyl into and through the buccal to the vascular system from where the agent is transported to the specific opioid receptor sites in the CNS. Compared with OTFC, data in healthy volunteers show that the effervescence reaction employed in FBT increases the total amount and the speed of absorption of fentanyl being absorbed. Compared with OTFC there is an increase in peak fentanyl blood concentrations, and an enhancement of the amount of buccal delivery of fentanyl. Such favorable data are underlined by the results of clinical studies where the FBT technology was studied in patients with breakthrough pain in chronic malignant pathologies.

Relative Bioavailability of Fentanyl Following Various Dosing Regimens of Fentanyl Buccal Tablet in Healthy Japanese Volunteers

Background

Fentanyl buccal tablet (FBT; FENTORA®, Cephalon, Inc., Frazer, PA, USA) is indicated in the US for breakthrough pain in patients with cancer who are already receiving and are tolerant to around-the-clock opioid therapy for underlying persistent cancer pain. For each individual patient, FBT should be titrated to the effective dose.

Objective

The primary objective was to characterize the pharmacokinetic parameters of FBT 400 µg administered as a single 400 µg tablet (regimen A) or as two 200 µg tablets given simultaneously (regimen B) and determine whether these are bioequivalent in healthy Japanese volunteers. Regimen C (two 200 µg tablets 30 minutes apart) was also compared as a secondary objective.

Methods

Healthy Japanese adults received regimens A, B, and C in a crossover fashion. Naltrexone was given to minimize the opioid effects of fentanyl. Serum fentanyl concentrations were determined in venous blood collected through 36 hours post dose. Regimens were declared bioequivalent with respect to bioavailability (as reflected by AUC_0–∞, AUC_0–last, and C_max) if the 90% confidence interval (CI) of the regimens' ratio fell within 0.80–1.25 (80%–125%).

Results

Twenty-nine volunteers (13 men, 16 women) were enrolled; 24 completed the study. Regimens A and B had bioequivalent systemic exposure parameters (B/A [90% CI]: AUC_0–∞108.4 [103.4, 113.7], AUC_0–last 106.1 [100.7, 111.7], and C_max 92.3 [83.2, 102.4]). Regimen C was bioequivalent to both A and B for AUCs, but only to B for C_max. Median time to C_max was 45 minutes for regimen A and 60 minutes for regimens B and C. The most frequent AEs were dizziness, application-site erythema, headache, somnolence, nausea, and vomiting. All AEs were mild or moderate.

Conclusions

Bioavailability of fentanyl after FBT 400 µg administered as a single tablet was bioequivalent to that after 2 simultaneously administered 200 µg tablets in healthy Japanese volunteers. AEs were mild or moderate.

Dose Proportionality of Fentanyl Buccal Tablet in Healthy Japanese Volunteers

OBJECTIVE: This study was conducted to assess the dose proportionality, safety, and tolerability of fentanyl buccal tablet (FBT) in Japanese volunteers. METHODS: Healthy, opioid-naive Japanese adults received single-dose FBT 100, 200, 400, and 800 microg in a randomized, open-label, crossover fashion. Naltrexone was given to minimize the opioid effects of fentanyl. Peak serum fentanyl concentration (C(max)), time to C(max) (t(max)), area under the serum fentanyl concentration-time curve (AUC) from time 0 to infinity (AUC(0-infinity)), and AUC from 0 to the last quantifiable concentration (AUC(0-last)) were summarized using descriptive statistics. Dose proportionality was claimed if the ln-ln plots of C(max), AUC(0-infinity), and AUC(0-last) vs. dose were linear and the 90% confidence intervals (CI) of the slopes were within 0.8927 and 1.1073. The safety population comprised volunteers who received >/=1 FBT. RESULTS: Twenty-five volunteers were enrolled, 23 were included in the safety population (mean age 35.3 years), and 19 completed the study. The assessment of dose proportionality did not meet the statistical criteria (slope [90% CI]: 0.9118 [0.8601, 0.9635] for C(max), 1.0756 [1.0377, 1.1136] for AUC(0-infinity), and 1.0992 [1.0677, 1.1307] for AUC(0-last)). However, the increase in systemic exposure with dose appeared linear, and a post hoc analysis of partial AUCs from time 0 to 8, 12, 18, and 24 hours supported dose proportionality. Median t(max) of 90 minutes (range 30-180 minutes) was independent of dose. Adverse events (AEs) were mild or moderate. The most frequent AEs were nausea (N = 9), dizziness (N = 8), headache (N = 6), somnolence (N = 6), dyspepsia (N = 5), and vomiting (N = 3). No application-site or serious AEs were reported. CONCLUSIONS: Systemic exposure to FBT was approximately dose proportional across the range 100 microg to 800 microg in healthy Japanese adults. Adverse events were mild or moderate.

Extent of Fentanyl Accumulation Following Multiple Doses of Fentanyl Buccal Tablet 400 microg in Healthy Japanese Volunteers

Objective

This study was conducted to characterize the pharmacokinetics, including extent of accumulation, and safety and tolerability of fentanyl following multiple doses of fentanyl buccal tablet (FBT) in healthy Japanese volunteers.

Methods

Healthy Japanese adults received 10 successive doses of open-label FBT 400 µg at 6-hour intervals. Naltrexone was given to minimize the opioid effects of fentanyl. FBT was placed above a molar tooth between the gum and cheek. Peak serum fentanyl concentration (C_max), time to C_max (t_max), and area under the serum fentanyl concentration-time curve from 0 to 6 hours (AUC_0–6) were summarized using descriptive statistics. Accumulation ratio was calculated as C_max for dose 10/C_max for dose 1, and was calculated similarly for AUC_0–6.

Results

Fourteen volunteers (mean age 33 years) were enrolled, and 13 completed the study. After doses 1 and 10, respectively, mean (SD) C_max was 1.70 (0.49) ng/mL and 1.97 (0.42) ng/mL, AUC_0–6 was 4.46 (1.14) ng·h/mL and 6.81 (0.90) ng·h/mL, and median (range) t_max was 50 (30–110) minutes and 30 (15–120) minutes. Following 10 successive doses, systemic exposure (AUC_0–6) was 55% higher than after dose 1, and C_max was 23% higher. Steady state was achieved within 3 days of dosing at 6-hour intervals, i.e., prior to dose 10. The most frequent adverse events (AEs) were somnolence (N = 9), decreased oxygen saturation (N = 4), headache (N = 3), application-site pain (N = 8), application-site erythema (N = 6), and application-site reaction (N = 5). All AEs were mild or moderate.

Conclusions

Following administration of FBT at 6-hour intervals to healthy Japanese volunteers, at steady state, fentanyl exposure was higher by 55% (AUC_0–6) and 23% (C_max) than after a single dose of FBT. Adverse events were mild or moderate.

Management of breakthrough pain in patients with cancer

Breakthrough pain (BTP) in patients with cancer lacks a consensus definition and is subsequently inadequately diagnosed and assessed, therefore making it more challenging to manage. Cancer pain is generally moderate to severe in intensity and persistent in nature. Despite the problematic definition of BTP, it is generally described as having similar intensity, but may also be transitory and variable in predictability. Most breakthrough analgesia fails to be effective in the time required for BTP. No useful analgesia is therefore provided but drug adverse effects escalate. Cancer pain management relies on the WHO analgesic ladder. The frequency of BTP and its inadequate management means that it has significant adverse effects on patients, their families and those involved in their care. This article outlines a systematic, clinical and evidence-based approach to managing BTP in patients with cancer that emphasizes a holistic approach and an understanding of multidimensional 'total pain'. Guidelines for managing BTP are presented and areas of developing research are identified.

Effect of buccal dwell time on the pharmacokinetic profile of fentanyl buccal tablet

BACKGROUND

The time fentanyl buccal tablet (FBT) takes to completely dissolve after placement on the buccal mucosa (i.e., 'dwell time') could exceed the time to onset of analgesia.

OBJECTIVE

To examine the relationship between FBT dwell time and fentanyl pharmacokinetic parameters.

RESEARCH DESIGN AND METHODS

This was a post hoc exploratory analysis of data from two randomized, open-label, crossover, pharmaco-kinetic studies that were designed to assess dose proportionality within the anticipated therapeutic dose range. Healthy adults received single FBT doses of 200-1080 microg in Study 1 (n = 28) and 270-1300 microg in Study 2 (n = 42).

MAIN OUTCOME MEASURES

Assessments included buccal dwell time, defined as the duration of FBT presence in the oral cavity, and the following pharmacokinetic measures: maximum serum concentration (C(max)), time to C(max) (T(max)) and area under the concentration-time curve (AUC; exposure) from 0 minutes to median T(max) adjusted for the dose (T(max')) (AUC(0 T(max'))). Spontaneously reported adverse events were recorded.

RESULTS

Mean buccal dwell time for FBT across the dose range varied from 14 to 25 minutes (range 3 - 62 minutes). There was no evidence of an association between FBT dwell time and values for T(max) (medians 45 - 60 minutes), dose-normalized C(max) (means 0.42-0.66 pg/ml/200 microg) or dose-normalized AUC(0 T(max')) (means 0.24-0.38 pg x h/ml/200 microg) over the range of FBT doses delivered. All adverse events reported were mild to moderate; none were unexpected or serious.

CONCLUSION

The pharmacokinetic parameters of FBT did not appear to be related to its buccal dwell time.

Fentanyl buccal tablet: faster rescue analgesia for breakthrough pain?

Breakthrough pain (BTP) is an unmet clinical need that is still poorly diagnosed, evaluated and inadequately treated. The prevalence of BTP has been estimated to affect at least 64% of cancer patients. Two pain-relief strategies were proposed: preventive and active ('rescue'). Oral short-acting opioid seems to be the most popular approach for BTP treatment, however, it is likely to be inadequate for a substantial proportion of patients as a result of the slow-onset of most available opioid preparations. Fentanyl buccal tablet (FBT) is a novel delivery system for fentanyl citrate. FBT utilizes OraVescent technology to improve bioavailability and speed of drug delivery. Recent studies have demonstrated superior pharmacokinetic profiles when compared with other available transmucosal opioids (OTFC), however, pharmacodynamic data are still somewhat limited.

Fentanyl Effervescent Buccal Tablet

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