Clinical pharmacokinetics of transdermal opioids: focus on transdermal fentanyl

Transdermal matrix fentanyl membrane patch (matrifen): in severe cancer-related chronic pain

The matrix fentanyl membrane patch is a new transdermal patch designed with a reduced drug load compared with established reservoir and matrix fentanyl patches. The drug is contained within a silicone matrix with a rate-controlling membrane designed to maintain constant serum fentanyl concentrations over the 72-hour application period. The matrix fentanyl membrane patch was equivalent to the reservoir fentanyl patch in terms of transdermal delivery of fentanyl, as demonstrated after both single (100 microg/h) and multiple (50 microg/h) applications by the peak serum fentanyl concentration and the area under the serum concentration-time curve over 72 hours. In a randomized, nonblind, multicentre trial, the transdermal matrix fentanyl membrane patch was noninferior to standard opioid therapy (transdermal reservoir or matrix fentanyl patch or an oral opioid) in terms of analgesic efficacy over 30 days in patients with cancer-related chronic pain requiring long-term opioid use. The transdermal matrix fentanyl membrane patch was as well tolerated as standard opioid therapy; patient-rated tolerability scores for constipation, nausea, daytime drowsiness and sleep disturbance were similar between treatments.

Management of chronic pain in the elderly: focus on transdermal buprenorphine

Chronic pain in the elderly is a significant problem. Pharmacokinetic and metabolic changes associated with increased age makes the elderly vulnerable to side effects and overdosing associated with analgesic agents. Therefore the management of chronic cancer pain and chronic nonmalignant pain in this growing population is an ongoing challenge. New routes of administration have opened up new treatment options to meet this challenge. The transdermal buprenorphine matrix allows for slow release of buprenorphine and damage does not produce dose dumping. In addition the long-acting analgesic property and relative safety profile makes it a suitable choice for the treatment of chronic pain in the elderly. Its safe use in the presence of renal failure makes it an attractive choice for older individuals. Recent scientific studies have shown no evidence of a ceiling dose of analgesia in man but only a ceiling effect for respiratory depression, increasing its safety profile. It appears that transdermal buprenorphine can be used in clinical practice safely and efficaciously for treating chronic pain in the elderly.

Transdermal drug pharmacokinetics in man: Interindividual variability and partial prediction

A database of human dermatopharmacokinetic parameters of 12 transdermal patches is established. The effect of system design, application site, and metabolism on pharmacokinetic data is discussed, and interindividual variability of data and its possible sources evaluated. Using multiple regression analysis, two equations based on drugs physicochemical characteristics are suggested for partial prediction of peak plasma concentration (C(max)) after patch application. Patch application presumably decreases variance as rub-off, wash and exfoliation steps are diminished. The results showed that interindividual variation, in terms of coefficient of variation (CV) of C(max), is inversely correlated with drugs molecular weight and lipophilicity in the range of 200<MW<400 and 1.6<logK(oct)<4.3. Multiple regression analysis of C(max) against physichochemical parameters demonstrated the prominent contribution of hydrogen bonding acceptability of the molecules on their maximal plasma concentration after patch administration. The findings suggest that the serum concentration profile for transdermal therapeutic systems (TTS) is a net result of the system performance, drug absorption and elimination. Thus, the variability in serum concentration is a function of variability of each process involved. This should be noted in explanation of effect of molecular features of drugs on their plasma concentration profile.

Efficacy, safety and pharmacokinetic study of a novel fentanyl-containing matrix transdermal patch system in Japanese patients with cancer pain

BACKGROUND AND OBJECTIVES

A novel transdermal matrix patch delivery system for fentanyl has been developed to deliver improved management of cancer pain compared with that obtained using current fentanyl reservoir patches. This study was carried out to assess the efficacy, safety and pharmacokinetic profiles of a 12.5 microg/h transdermal matrix fentanyl patch administered with the objective of replacing morphine, oral oxycodone or fentanyl injection formulations. The study also evaluated how the pharmacokinetic profiles of higher dose fentanyl patches (25, 37.5 and 50 microg/h) changed following dose adjustments to optimize management of cancer pain.

METHODS

This open-label, multicentre study involved 87 patients of both sexes (> or =20 years) with a confirmed diagnosis of cancer. Patients were receiving any one of the following at the time of enrollment for the management of their cancer pain: (a) morphine <45 mg/day orally, <30 mg/day as suppositories, or <15 mg/day by injection; (b) oral oxycodone <30 mg/day; or (c) fentanyl injectable preparations <0.3 mg/day. The patients were administered a 3-day course of fentanyl transdermal matrix patch application three times. The initial dose was 12.5 microg/h, which could be increased when a new patch was applied if the physician deemed this to be appropriate based on pain intensity ratings and use of rescue medications. Efficacy outcomes included patients' global assessment scores (primary efficacy endpoint) measured on a five-step scale and dichotomous scores for physicians' global assessment. The occurrence of adverse events and changes in laboratory tests were evaluated as safety variables. Serum fentanyl levels were measured immediately after removal of the old patch on days 4, 7 and 10 to obtain data on trough serum concentrations.

RESULTS

The percentage of patients in category 3 or higher (very satisfied, satisfied, or neither satisfied nor dissatisfied) for the patient's global assessment score was 89.4% (76/85), indicating high patient satisfaction and attainment of sufficient pain control after patients switched from their previously used opioid analgesics. Similar findings were obtained on physicians' global assessment scores. A total of 316 adverse events occurred in 78 (90.7%) of 86 patients who were administered at least one patch. These included nausea (31 [36.0%]), somnolence (26 [30.2%]), vomiting (22 [25.6%]), diarrhoea (17 [19.8%]), constipation (14 [16.3%]), pyrexia (11 [12.8%]) and insomnia (9 [10.5%]). The mean (+/- SD) serum fentanyl concentration determined on day 4 was 169.9 +/- 103.4 pg/mL (n = 83). Serum fentanyl measurement results indicated that the same fentanyl patch dose resulted in similar serum fentanyl levels, while increased doses produced higher serum fentanyl concentrations.

CONCLUSION

The fentanyl matrix transdermal patch formulation employed in this study demonstrated sufficient cancer pain control for patients switching from morphine or oral oxycodone preparations. The patch tested was well tolerated and its use did not result in any increased incidence of adverse drug reactions over those commonly found with opioid analgesics.

Subcutaneous injection of inhaled anesthetics produces cutaneous analgesia

PURPOSE

Previous investigations suggest that inhaled anesthetics may produce cutaneous analgesia. The objective of this study was to evaluate whether inhaled anesthetics have a direct analgesic effect on skin.

METHODS

We conducted subcutaneous injections of one of three inhaled anesthetics (halothane, isoflurane, and enflurane) or one of two local anesthetics (lidocaine and procaine) at various dosages in rats (n=6 rats, for each dose of each drug). Subcutaneous injections of vehicles (saline or olive oil) were used as controls (n=6 rats for each vehicle). We constructed concentration-response curves, wherein the concentrations of drugs tested in subcutaneous tissue fluid were estimated by calculation, and the cutaneous analgesic effects of drugs were evaluated by pinprick tests on skin.

RESULTS

Like local anesthetics, subcutaneous injection of inhaled anesthetics produced concentration-dependent, cutaneous analgesia which attained maximum (complete cutaneous analgesia) at high concentration. This effect was reversible and localized in the area of injection. On the basis of 50% effective concentration, the ranking of potencies was lidocaine>halothane>isoflurane>enflurane>procaine (P<0.05 for all differences). Subcutaneous injections of vehicles did not produce cutaneous analgesia.

CONCLUSIONS

Like local anesthetics (lidocaine and procaine), subcutaneous injections of inhaled anesthetics (halothane, isoflurane, and enflurane) produced a concentration-dependent, cutaneous, analgesic effect at the site of injection. Inhaled anesthetics have a direct analgesic effect on skin.

Management of malignant bowel obstruction

Malignant bowel obstruction (MBO) is a common and distressing outcome particularly in patients with bowel or gynaecological cancer. Radiological imaging, particularly with CT, is critical in determining the cause of obstruction and possible therapeutic interventions. Although surgery should be the primary treatment for selected patients with MBO, it should not be undertaken routinely in patients known to have poor prognostic criteria for surgical intervention such as intra-abdominal carcinomatosis, poor performance status and massive ascites. A number of treatment options are now available for patients unfit for surgery. Nasogastric drainage should generally only be a temporary measure. Self-expanding metallic stents are an option in malignant obstruction of the gastric outlet, proximal small bowel and colon. Medical measures such as analgesics according to the W.H.O. guidelines provide adequate pain relief. Vomiting may be controlled using anti-secretory drugs or/and anti-emetics. Somatostatin analogues (e.g. octreotide) reduce gastrointestinal secretions very rapidly and have a particularly important role in patients with high obstruction if hyoscine butylbromide fails. A collaborative approach by surgeons and the oncologist and/or palliative care physician as well as an honest discourse between physicians and patients can offer an individualised and appropriate symptom management plan.

Morphine bioavailability from a topical gel formulation in volunteers

Although available therapies provide relief to many patients with cancer-related pain, swallowing difficulties or intestinal obstruction may preclude oral analgesic delivery in some. Topical morphine might provide an alternate delivery form but morphine bioavailability from a topical gel formulation has not been reported in humans. We conducted a randomized, placebo-controlled, double-blind, crossover study of five volunteers after they provided institutionally-approved, written, informed consent. They were admitted to the Northwestern University General Clinical Research Center twice, being randomly assigned to receive either 1mL of morphine compounded at 10mg/mL in pluronic lecithin organogel (PLO) base applied to the wrist and 1mL of normal saline administered subcutaneously, or 1mL of topical drug-free PLO base and 1mL of subcutaneous morphine, 3mg/mL, the first time and the opposite combination the second. Seventeen blood samples were collected from 5minutes to 10hours after dose administration for morphine concentration determination. Plasma samples were prepared by solid-phase extraction and morphine concentrations measured by a mass spectrometric technique with a linear range of 0.5-500ng/mL. Bioavailability of the topical formulation relative to the subcutaneous dose was to be estimated from doses and the plasma morphine concentration versus time relationships. Because morphine was seldom detected in plasma samples after topical administration and was unquantifiable when it was, the low bioavailability of topical morphine was unquantifiable. These results suggest that topical administration of morphine compounded in a PLO base for transdermal drug delivery is unlikely to provide relief of cancer-related pain.

Effect of voriconazole and fluconazole on the pharmacokinetics of intravenous fentanyl

OBJECTIVE

Fentanyl is a widely used opioid analgesic, which is extensively metabolized by hepatic cytochrome P450 (CYP) 3A. Recent reports suggest that concomitant administration of CYP3A inhibitors with fentanyl may lead to dangerous drug interactions.

METHODS

The potential interactions of fentanyl with triazole antifungal agents voriconazole and fluconazole were studied in a randomized crossover study in three phases. Twelve healthy volunteers were given 5 microg/kg of intravenous fentanyl without pretreatment (control), after oral voriconazole (400 mg twice on the first day and 200 mg twice on the second day), or after oral fluconazole (400 mg once on the first day and 200 mg once on the second day). Plasma concentrations of fentanyl, norfentanyl, voriconazole, and fluconazole were determined up to 24 h. Pharmacokinetic parameters were calculated using compartmental methods.

RESULTS

The mean plasma clearance of intravenous fentanyl was decreased by 23% (range -22 to 48%; p < 0.05) and 16% (-34 to 53%; p < 0.05) after voriconazole and fluconazole administration, respectively. Voriconazole increased the area under the fentanyl plasma concentration-time curve by 1.4-fold (p < 0.05). The initial plasma concentrations and volume of distribution of fentanyl did not differ significantly between phases.

CONCLUSION

Both voriconazole and fluconazole delay the elimination of fentanyl significantly. Caution should be exercised, especially in patients who are given voriconazole or fluconazole during long-lasting fentanyl treatment, because insidiously elevated fentanyl concentration may lead to respiratory depression.

Impact of transdermal fentanyl on quality of life in rheumatoid arthritis

OBJECTIVES

The purpose of the study was to investigate the effectiveness and tolerability of transdermal fentanyl in a treatment regimen in patients with rheumatoid arthritis (RA).

METHODS

Two hundred twenty-six patients (mean age 66 y) with severe pain caused by RA who had not previously been treated with transdermal fentanyl were included in this prospective, open-label study. Pain intensity, functional impairment, and well-being were documented prospectively for 30 days after treatment with transdermal fentanyl had been initiated. Patients evaluated pain on an 11-point numerical rating scale. Quality of sleep, daily and social functioning, and treatment satisfaction were rated using 5-point categorical rating scales. General well-being was assessed by the Marburg questionnaire.

RESULTS

Adding transdermal fentanyl to the ongoing RA therapy reduced pain intensity significantly from 8.0 (7.82 to 8.18) to 4.0 (3.75 to 4.25). Mean functional impairment due to pain also decreased significantly from "severe" at the beginning to "mild to moderate." Treatment with transdermal fentanyl also led to a significant improvement by approximately 1.5 units for all items in the Marburg questionnaire on general well-being. At the end of the study, nearly all patients were satisfied with the pain treatment. Transdermal fentanyl was generally well tolerated. The most frequent side effects were nausea (9.7%) and vomiting (7.1%).

DISCUSSION

Patients with pain caused by RA improved in terms of pain intensity, sleep, function, and general well-being when transdermal fentanyl was added to the treatment regimen. Treatment satisfaction was high. Transdermal fentanyl also demonstrated good tolerability over a period of 30 days.

Clinical experience with transdermal and orally administered opioids in palliative care patients--a retrospective study

BACKGROUND

Transdermal fentanyl is a widely used opioid for the treatment of cancer pain. Simplicity of use and high patient compliance are the main advantages of this opioid. However, based on our clinical experience, transdermal fentanyl is often not efficacious in terminally ill palliative care patients. We thus retrospectively examined the pain management and need for opioid switching in cancer patients admitted to our palliative care unit.

METHODS

Of 354 patients admitted to our palliative care unit from 2004 through 2005, 81 patients were pre-treated with transdermal fentanyl. Demographic and cancer-related data (diagnosis, symptoms, pain score on a numeric rating scale (NRS)), analgesic dose at admission and discharge were compared.

STATISTICS

mean +/- SD, ANOVA, Wilcoxon's test was used for inter-group comparisons, significance P < 0.05, adjusted for multiple testing. Pain scores are given in median (range).

RESULTS

Mean transdermal fentanyl dose at admission was 81.0 +/- 55.8 microg/h. In 79 patients transdermal fentanyl treatment was discontinued. In two patients, analgesic treatment according to WHO I provided sufficient pain relief. The other 77 patients were switched to other opioids: 33 patients to oral morphine and 44 to oral hydromorphone. In patients switched to morphine the dose at discharge (104.7 +/- 89.0 mg) was lower than at admission (165.5 mg morphine equivalence). In patients switched to hydromorphone the dose of 277.8 +/- 255.0 mg morphine equivalent was higher at discharge than at admission (218.2 +/- 131.4 mg morphine equivalence--considering an equianalgesic conversion ratio morphine: hydromorphone = 7.5: 1). Pain scores decreased significantly after opioid rotation (NRS at rest/on exertion: 4 (0-10)/7 (2-10) versus 1 (0-3)/2 (0-5); P < 0.001).

CONCLUSIONS

In the patient group switched to morphine, sufficient pain relief was achieved by lower equianalgesic morphine doses, compared with the doses at admission. In the patient group switched to hydromorphone, higher equianalgesic morphine doses were needed at discharge, considering an equianalgesic conversion ratio of morphine: hydromorphone = 7.5: 1. Patients with far advanced cancer often suffer from sweating and cachexia, which may have negative effects on the absorption of transdermal fentanyl. Opioid switching to oral morphine or hydromorphone was well tolerated and proved to be an efficacious option for cancer pain treatment.

Use of single-drop microextraction for determination of fentanyl in water samples

Fentanyl is a very potent synthetic narcotic analgesic. Because of its strong sedative properties, it has become an analogue of illicit drugs such as heroin. Its unambiguous detection and identification in environmental samples can be regarded as strong evidence of its illicit preparation. In this paper we report application of single-drop microextraction (SDME) for analysis of water samples spiked with fentanyl. Experimental conditions which affect the performance of SDME, for example the nature of the extracting solvent, sample stirring speed, extraction time, ionic strength, and solution pH, were optimized. The method was found to be linear in the concentration range 0.10-10 ng mL(-1). The limits of quantitation and detection of the method were 100 pg mL(-1) and <75 pg mL(-1), respectively. This technique is superior to other sample-preparation techniques because of the simple experimental set-up, short analysis time, high sensitivity, and minimum use of organic solvent.

Skin pretreatment with an Er:YAG laser promotes the transdermal delivery of three narcotic analgesics

Because of their low oral bioavailabilities and short half-lives, it may be more feasible to administer narcotic analgesics via the skin. However, this delivery method is limited by the low permeability of the stratum corneum (SC). The aim of this study was to enhance the transdermal delivery of three narcotic drugs, including morphine, nalbuphine, and buprenorphine, with an erbium:yttrium-aluminum-garnet (Er:YAG) laser pretreatment. In an in vitro pig skin permeation experiment, Er:YAG laser pretreatment of the skin produced a 10~35-fold enhancement in drug permeation that was dependent on the laser fluence and the narcotic analgesic used. The permeation of morphine and nalbuphine showed higher enhancement with Er:YAG laser treatment as compared to that of buprenorphine. This may have been due to the higher lipophilicity and molecular mass of buprenorphine than the other two narcotic drugs. A photomechanical wave was generated by filtering laser radiation through a polystyrene target. The experimental results showed that a single photomechanical wave was sufficient to enhance morphine permeation by sevenfold. This enhancement was significantly lower than that produced by direct laser irradiation, indicating the predominant mechanism of SC ablation by the Er:YAG laser for transdermal drug delivery.

Fentanyl HCl iontophoretic transdermal system (ITS): clinical application of iontophoretic technology in the management of acute postoperative pain

The fentanyl HCl iontophoretic transdermal system (fentanyl ITS) is a novel patient-controlled analgesia (PCA) system that has been approved in the USA and Europe for the management of acute, moderate-to-severe postoperative pain. This system extends the applicability of transdermal drug delivery to acute pain management, allowing patients to self-administer pre-programmed doses of fentanyl non-invasively through the use of iontophoretic technology. Iontophoresis is the process by which an electric current is used to drive ionized drug molecules across the skin and into the systemic circulation. Results of a recent US clinical trial found the fentanyl ITS to provide pain control equivalent to a standard regimen of morphine i.v. PCA, with a similar incidence of opioid-related adverse events. The fentanyl ITS may offer a number of clinical advantages over existing PCA modalities. Its method of drug delivery avoids the risk of complications from needle-related injuries and infection, and its pre-programmed electronics eliminate the potential for manual programming errors and excessive dosing. In addition, the compact size of the system could enable greater patient mobility following surgery. The fentanyl ITS has the potential to become a valuable option in the management of acute postoperative pain.

Validated GC–MS analysis for the determination of residual fentanyl in applied Durogesic® reservoir and Durogesic® D-Trans® matrix transdermal fentanyl patches

The method development and validation characteristics are described of a simple gas chromatographic-mass spectrometric (GC-MS) analytical procedure to determine residual fentanyl in used Durogesic reservoir patches and Durogesic D-Trans matrix technology based systems to estimate the actual rate of transdermal fentanyl delivered in individual patients. The sample preparation protocol constituting a saline based extraction of sets of new patches of each nominal dose available, resulted in fentanyl extraction recoveries to increase steadily as a function of increasing extraction time. For the reservoir type transdermal therapeutic system (TTS), fentanyl extraction efficiencies at equilibrium (16 h) ranged from approximately 60% (100-microg/h TTS) to 95% (25-microg/h TTS), whereas for the matrix type system considerable lower recoveries were demonstrated for the highest nominal dose rates (35%-52%), while reaching 90% for the 25-microg/h system. For the latter type of fentanyl TTS, an optimized methanol based extraction protocol yielded virtually quantitative fentanyl recoveries for each matrix patch nominal dose level at substantially shorter extraction periods (15 min). The GC-MS analytical method using selected ion monitoring (SIM) and deuterated fentanyl as internal standard was shown to be adequately selective with regard to the presence of other compounds in the Durogesic patches. It was further demonstrated that the developed analytical protocols provided highly reproducible and accurate estimates of the initial fentanyl content of each patch type at all available nominal doses, with coefficients of variation and relative errors generally below 10%. These advantageous assay validation characteristics can be further transposed to the application of residual fentanyl level estimates in used patches, provided that with each batch of samples also a set of new TTSs with equal dose is assayed to perfectly mimic extraction phenomena. Finally, the presented GC-MS analytical protocol was successfully applied for the determination of residual fentanyl in a subset of 57 reservoir type patches obtained from four palliative patients.

Effect of local administration of transdermal fentanyl on peripheral opioid analgesia

OBJECTIVE

Transdermal fentanyl is a commonly used analgesic for the treatment of severe chronic pain. Recent investigations have shown the presence of mu-opioid receptors in the skin and opioid analgesic efficacy with alternative routes of administration of narcotics. This placebo-controlled, double-blind prospective study assessed whether transdermal fentanyl administration produces local peripheral opioid analgesia at the site of application.

DESIGN

Baseline pain threshold and supra-threshold pain intensity assessments were measured using Quantitative Sensory Testing in 12 healthy volunteers. Placebo and fentanyl containing patches (Duragesic, 25 microg/h) were applied to opposite forearms for 2 h. After patch removal, pain threshold, supra-threshold pain response, and the area of secondary hyperalgesia were evaluated for both forearms.

RESULTS

No statistically significant differences in pain threshold, supra-threshold pain intensity, or area of hyperalgesia in fentanyl- versus placebo-treated forearms were detected in the study subjects.

CONCLUSION

These results suggest that the application of transdermal fentanyl patch for a period of 2 h does not produce local peripheral opioid analgesia at the site of patch application.

Regional differences in transdermal penetration of fentanyl through equine skin

The rate and regional differences for the penetration of fentanyl through equine skin was investigated in vitro using a commercial transdermal therapeutic system (TTS) or 'patch'. Skin collected from the thorax, groin and leg (dorsal metacarpal) regions of five horses was placed in diffusion cells and a fentanyl TTS applied to each skin sample. Drug penetration through each skin sample over 48 h measured using high performance liquid chromatography (HPLC). Cumulative penetration (microg/cm2) was plotted against time (h) and used to regress the steady state flux (microg/cm2/h) of fentanyl through each skin site. Results showed similar fluxes for both the thorax (2.32+/-0.17 microg/cm2/h and groin (2.21+/-0.11 (microg/cm2/h) regions, but significantly lower flux (P=<0.05) for the leg region (1.56+/-0.120 microg/cm2/h. Interestingly, there was a significantly longer lag time for the penetration of fentanyl through the groin region (7.87+/-0.51 h) compared to the other two sites (5.66+/-0.97 h and 5.75+/-0.43 h for the thorax and leg regions respectively). The results suggest that a fentanyl TTS applied to the leg region may have a small but significantly lower amount of fentanyl available systemically, compared to patches applied to the thorax or groin regions, which may affect the level of analgesia subsequently achieved in the horse.

Transdermal drug delivery: Basic principles for the veterinarian

The use of topical pharmaceutical formulations is increasingly popular in veterinary medicine. A potential concern is that not all formulations are registered for the intended species, yet current knowledge strongly suggests that simple extrapolation of transdermal drug pharmacokinetics and pharmacodynamics between species, including humans, cannot be done. In this review, an overview is provided of the underlying basic principles determining the movement of topically applied molecules into and through the skin. Various factors that may affect transdermal drug penetration between species, between individuals of a particular species and regional differences in an individual are also discussed. A good understanding of the basic principles of transdermal drug delivery is critical to avoid adverse effects or lack of efficacy when applying topical formulations in veterinary medicine.

Identification of exposure pathways for opioid narcotic analgesics in pharmaceutical production workers

The protection of workers from the potential harmful effects of active pharmaceutical ingredients (APIs) poses a significant challenge for the drug manufacturing industry. The actual pathways through which pharmaceutical production workers are exposed to potent drugs and the processes resulting in actual uptake are up till now virtually unknown. In this study, a detailed exposure assessment survey was conducted in a pharmaceutical 'primary manufacturing' production facility during which environmental and biological exposure monitoring for potent opioid narcotic drugs was performed. On the occasion of multiple consecutive production days, personal half-shift air samples were collected and hand wipes were taken at the end of each half-shift and analysed for fentanyl. All environmental samples showed detectable amounts of fentanyl (>0.1 ng per sample), indicating a potential for both inhalation and dermal exposure. Spatial distribution of fentanyl dermal contamination was further investigated by means of patch samplers placed on five anatomical regions of the body. Body locations showing the highest level of fentanyl contamination were identified as the hands, the neck and lower arms. The effective uptake of fentanyl was demonstrated by the detection of this opioid in urine samples of the workers involved. Individual and group-level analysis of combined external and internal fentanyl exposure measures revealed a positive and significant correlation between fentanyl hand exposure and urinary excretion, while it seemed that the effect of inhalation exposure was largely due to its correlation with dermal exposure. The results of the established individual linear and mixed effects models strongly suggest that in most workers the dermal pathway is actually the primary route of fentanyl exposure.

Opioid-induced gastrointestinal dysfunction

Use of opioid analgesics is associated with a number of side effects, especially opioid-induced gastrointestinal dysfunction. The extensive use of these compounds and the significant negative impact of the resulting gastrointestinal dysfunction on patients' quality of life make it an important clinical issue. In recent years our understanding of the mechanisms of opioid-induced gastrointestinal dysfunction has advanced greatly. This article reviews the underlying pathophysiological mechanisms of specific gastrointestinal adverse effects of opioids. The role of endogenous opioid peptides in certain gastrointestinal diseases is also discussed. A better understanding of the pathophysiological mechanisms of opioid-induced bowel dysfunction should lead to the development of newer opioid analgesics and improved regimens resulting in reduced gastrointestinal adverse effects.

Evaluation of the bioequivalence of two transdermal fentanyl systems following single and repeat applications

OBJECTIVE

Transdermal delivery of fentanyl has potential benefits over slow-release morphine, being largely preferred by patients owing to the combination of effective pain relief, a good safety profile and easy, pain-free dosing. The new drug-in-adhesive Durogesic D-TRANS fentanyl Matrix Delivery System (DDTDF) has improved pharmaceutical characteristics and patient acceptability compared to the original Durogesic transdermal reservoir system (fentanyl transdermal reservoir), whilst still providing reliable and consistent delivery of fentanyl. The bioequivalence of these two systems was evaluated in two studies.

RESEARCH DESIGNS AND METHODS

Eighty healthy volunteers received single (72 h) or multiple (288 h) applications of DDTDF and the transdermal reservoir system (100 microg/h) in two separate randomised, crossover bioequivalence studies. Bioequivalence was assessed by calculating the ratio of least squares means based on log-transformed data following single system application and at steady-state during the fourth application.

RESULTS

Both transdermal systems were bioequivalent with respect to all tested pharmacokinetic parameters. Inter-subject variability was comparable between the two systems and was greater than intra-subject variability. Transdermal delivery was well tolerated in both groups.

CONCLUSIONS

The pharmacokinetic results demonstrate that DDTDF is bioequivalent to the original fentanyl transdermal reservoir system after single and multiple applications.

Switching from reservoir to matrix systems for the transdermal delivery of fentanyl: a prospective, multicenter pilot study in outpatients with chronic pain

Matrix systems for transdermal fentanyl will replace the reservoir systems in Europe. In an industry-independent, prospective, multicenter pilot study, 46 outpatients with chronic pain were asked to assess pain intensity, sleep interference, adverse events, and multiple secondary parameters during administration of the last reservoir and the first two matrix patches. There was no difference in pain intensity, sleep interference, and the rate of adverse events between both systems. Self assessment on a 6-step numeric rating scale (1 = very good, 6 = insufficient) comparing the two systems (reservoir vs. matrix) showed that skin compatibility (2.6 vs. 1.5), adhesive properties (3.2 vs. 1.8), wearability/comfort (2.8 vs. 1.5), and general satisfaction (2.5 vs. 1.8) improved significantly with the new matrix technology. At study endpoint, 91% of patients preferred the matrix system for future use. The new fentanyl matrix system is characterized by a high level of general satisfaction, ease of use, patient acceptance, and improved skin compatibility. Reservoir and matrix systems appear to have comparable efficacy and safety so that outpatients can be switched directly from the reservoir to the matrix system without difficulties and new dose titration.

Transdermal buprenorphine in clinical practice--a post-marketing surveillance study in 13,179 patients

OBJECTIVE

The objective of this post-marketing surveillance study was to collect effectiveness and safety data on the labelled use of buprenorphine transdermal patches (Transtec*) under routine clinical conditions.

RESEARCH DESIGN AND METHODS

For this open, observational study, patients with moderate to severe cancer or non-cancer pain requiring treatment with an opioid analgesic were recruited at hospitals, outpatient clinics and general practitioners' practices in Germany. Buprenorphine transdermal patches (35 microg/h, 52.5 microg/h or 70 microg/h) were prescribed at physicians' discretion in accordance with the product's Summary of Product Characteristics (SmPC). Patients assessed their pain relief as 'very good', 'good', 'satisfactory', 'poor' or 'no effect'. Investigators were instructed to report all adverse events throughout the observation period. On completion, effectiveness and tolerability were evaluated for the overall study population, cancer and non-cancer patients, and patients < 70 years and > or = 70 years. Other analyses assessed pain relief with respect to previous opioid treatment and increased patch strength, and in patients who remained on their original dose. The total observation time was 9 months, and the average individual documented treatment time was 60.8 days.

RESULTS

A total of 13,179 patients were evaluated; 3690 (28%) with cancer pain and 9489 (72%) with non-cancer pain. The most frequent diagnoses in non-cancer patients were musculoskeletal disorders (77%) and neuropathy (23%). In the great majority of cases (78%), treatment was started with the 35 microg/h patch. The initial dose needed to be increased subsequently only in about 18% of subjects. Buprenorphine transdermal patches provided effective, sustained and dose-dependent analgesia in patients with cancer and non-cancer pain, irrespective of the patients' age or pain syndromes. Whereas good or very good pain relief was documented only for 6% of the patients with the initial assessment, this percentage increased to 71% at the first follow-up and 80% at the final assessment. Fewer than 5% of subjects discontinued treatment owing to unsatisfactory pain relief. Altogether, adverse events were documented for 2874 patients (22%), whereas a relationship with trans dermal buprenorphine (adverse drug reactions) was assumed for only 10% (2220 adverse drug reactions in 1330 patients). The tolerability profile was as expected for an opioid and did not vary to a relevant extent with either the patient's age or the cause of pain (cancer or non-cancer). No evidence emerged of any previously unknown side effects.

CONCLUSIONS

Buprenorphine transdermal patches are well tolerated and effective in the treatment of chronic cancer and non-cancer pain, irrespective of the patients' age. There was no clinically relevant development of tolerance.

Stark wirksame Opioidanalgetika und Obstipation

In cancer pain therapy treatment with strong opioids is essential. However, it may be accompanied by the occurrence of various adverse effects. The most frequent and persistent side effect in the course of opioid treatment is constipation. It is mainly caused by linkage of the opioid to the peripheral mu-receptors in the bowel and may increase as a result of certain concomitant circumstances, such as poor intake of fluids or electrolyte disorder. Present research indicates that there is a relation between type of opioid and degree of constipation, i.e. treatment with transdermal fentanyl or methadone tends to cause less constipation compared to morphine or hydromorphone. The route of administration of morphine--oral vs. subcutaneous--does not seem to affect the incidence of opioid-induced constipation. Furthermore, prophylaxis and efficient control of opioid-induced constipation still fail to be part of the routine in pain treatment.

Compartmental Modeling of Transdermal Iontophoretic Transport II: In Vivo Model Derivation and Application

PURPOSE

This study was aimed to develop a family of compartmental models to describe in a strictly quantitative manner the transdermal iontophoretic transport of drugs in vivo. The new models are based on previously proposed compartmental models for the transport in vitro.

METHODS

The novel in vivo model considers two separate models to describe the input into the systemic circulation: a) constant input and b) time-variant input. Analogous to the in vitro models, the in vivo models contain four parameters: 1) kinetic lag time (tL), 2) steady-state flux during iontophoresis (JSS), 3) skin release rate constant (KR), and 4) passive flux in the post-iontophoretic period (Jpas). The elimination from the systemic circulation is described by a) the one-compartment and b) the two-compartment pharmacokinetic models. The models were applied to characterize the observed plasma concentration vs. time data following single-dose iontophoretic delivery of growth hormone-releasing factor (GRF) and R-apomorphine. Moreover, the models were also used to simulate the observed plasma concentration vs. time profiles following a two-dose transdermal iontophoretic administration of alniditan.

RESULTS

The time-variant input models were superior to the constant input models and appropriately converged to the observed data of GRF and R-apomorphine allowing the estimation of JSS, KR, and Jpas. In most cases, the values of tL were negligible. The estimated JSS and the in vivo flux profiles of GRF and R-apomorphine were similar to those obtained using the deconvolution method. The two-dose iontophoretic transport of alniditan was properly simulated using the proposed time-variant input model indicating the utility of the model to predict and to simulate the drug transport by a multiple-dose iontophoresis. Moreover, the use of the compartmental modeling approach to derive an in vitro-in vivo correlation for R-apomorphine was demonstrated. This approach was also used to identify the optimum in vitro model that closely mimics the in vivo iontophoretic transport of R-apomorphine.

CONCLUSIONS

The developed in vivo models demonstrate their consistency and capability to describe the in vivo iontophoretic drug transport. This compartmental modeling approach provides a scientific basis to examine in vitro-in vivo correlations of drug transport by iontophoresis.

[Effectiveness of a pharmaceutical care unit for the control of severe chronic pain]

INTRODUCTION

The effectiveness of a pharmaceutical care unit was assessed within a staged program for non-malignant severe chronic pain control in a multidisciplinary pain management unit at Consorcio Hospital General Universitario, Valencia, Spain.

MATERIALS AND METHODS

One hundred and fifty patients with clinical indication for a major opioid were included in WHO's third analgesic rung by our medical team following careful triage. The pharmaceutical care unit, or phase II, monitored dosage titration for pain stabilization with absence of side effects, as well as the onset of subsequent chronic therapy.

RESULTS

Upon program completion 75% of patients had their pain under control, having required 22.7 days on average for opiate dose titration. Mean daily dose was 22.3 mg, and constipation was prophylactically managed from the start. Fifty-nine percent of patients received subsequent chronic therapy with fentanyl transdermal patches at 25 microg/h; 10% followed suit with oral morphine solution, and 6% with controlled-release morphine. Twenty-five percent of the remaining patients had relevant events during the therapy titration stage, which led to therapy discontinuation and discharge because of lack of therapeutic effectiveness. After 24 months 70% of patients were still on initial doses.

CONCLUSIONS

The effectiveness of our unit was demonstrated by the achievement of the program objectives.

Pharmacology of palliative medicine

OBJECTIVE

To describe the concepts of both pharmacokinetics and pharmacodynamics and how it applies to palliative medicine.

DATA SOURCES

Research and review articles and textbooks.

CONCLUSION

Most patients who have an illness that requires palliation are elderly, have co-morbid conditions, and are on many medications. Both age and disease can alter the way drugs are handled by the body (pharmacokinetics) and how they affect the body (pharmacodynamics).

IMPLICATIONS FOR NURSING PRACTICE

The oncology nurse, armed with the correct knowledge about medications, can have an important inmpact on improving the patient's care, safety, and quality of life.

Utilisation pattern of fentanyl transdermal system in The Netherlands

PURPOSE

To describe the utilisation pattern of TTS fentanyl in daily practice.

METHODS

A retrospective cohort study was performed with data from the Dutch PHARMO system, including medication and hospital admission records of 850,000 inhabitants of 25 Dutch cities. New starters of TTS fentanyl with at least two consecutive prescriptions in the period of 1 January 1996 through 31 December 2001 were included in the study cohort. Patients were distinguished in having non-cancer or cancer pain.

RESULTS

About 61% of the patients suffered from non-cancer pain and 60% used other opioids before start of TTS fentanyl. The majority of the patients used other pain medication during the first treatment episode. Most patients (74%) started treatment with the lowest dose of TTS fentanyl (25 microg/hour), patients with cancer pain more often started with higher doses. About half of the patients changed type of patch during the first treatment episode, 80% of these patients had an increase in dose of TTS fentanyl. Fifty percent of all patients had a first treatment episode of less than 2 months and more than one third did not renew their prescription within two months. The median number of days of use per patch was 2.2 days for all patients.

CONCLUSIONS

The use of TTS fentanyl is limited to a short period of time for a substantial percentage of patients starting treatment. The median duration of use per TTS fentanyl patch i.e. 2.2 days, was lower than the 3 days application period recommended in the summary of product characteristics.

Efficacy, safety, and steady-state pharmacokinetics of once-a-day controlled-release morphine (MS Contin XL) in cancer pain

The efficacy, safety, and pharmacokinetics of a novel once-daily morphine formulation (OAD morphine) and a 12-hourly formulation (twice-daily CR morphine) were compared in a double-blind, multi-centered crossover study. Chronic cancer pain patients (n=25) were randomized to OAD morphine (mean 238 +/- 319 mg q24h) or twice-daily CR morphine (mean 119 +/- 159 mg q12h) for one week. They then crossed over to the alternate drug, which also was taken for one week. There was no difference between treatments for evaluations of overall pain intensity, analgesic efficacy, or adverse events. However, whereas pain scores increased during the day on twice-daily CR morphine (P=0.0108), they remained stable on OAD morphine. Most patients (68%) chose once-daily dosing for continuing pain management (P=0.015). The AUC ratio was 100.3%, indicating equivalent absorption. Fluctuation indices were 93.5 +/- 28.8% and 179.3 +/- 41.3% (P=0.0001) for OAD morphine and twice-daily CR morphine, respectively. OAD morphine provides analgesia similar to twice-daily CR morphine with reduced fluctuation in plasma morphine concentration and more stable pain control.

Investigation of in vitro transdermal absorption of fentanyl from patches placed on skin samples obtained from various anatomic regions of dogs

OBJECTIVE

To investigate in vitro transdermal absorption of fentanyl from patches through skin samples obtained from various anatomic regions of dogs.

SAMPLE POPULATION

Skin samples from 5 Greyhounds.

PROCEDURE

Skin samples from the dogs' thoracic, neck, and groin regions were collected postmortem and frozen. After samples were thawed, circular sections were cut and placed in Franz-type diffusion cells in a water bath (32 degrees C). A commercial fentanyl patch, attached to an acetate strip with a circular hole, was applied to each skin sample. Cellulose strips were used as control membranes. Samples of receptor fluid in the diffusion cells were collected at intervals for 48 hours, and fentanyl concentrations were analyzed by use of high-performance liquid chromatography.

RESULTS

Mean+/-SD release rate of fentanyl from the patch, defined by its absorption rate through the non-rate-limiting cellulose membrane, was linear during the first 8 hours (2.01+/-0.05 microg/cm2 of cellulose membrane/h) and then decreased. Fentanyl passed through skin from the groin region at a faster rate and with a significantly shorter lag time, compared with findings in neck or thoracic skin samples.

CONCLUSIONS AND CLINICAL RELEVANCE

In vitro, fentanyl from a patch was absorbed more quickly and to a greater extent through skin collected from the groin region of dogs, compared with skin samples from the thoracic and neck regions. Placement of fentanyl patches in the groin region of dogs may decrease the lag time to achieve analgesia perioperatively; however, in vivo studies are necessary to confirm these findings.

Opioid switching from transdermal fentanyl to oral methadone in patients with cancer pain

BACKGROUND

Patients with cancer often are rotated from other opioids to methadone to improve the balance between analgesia and side effects. To the authors' knowledge, no clear guidelines currently exist for the safe and effective rotation from transdermal fentanyl to methadone.

METHODS

The authors evaluated a protocol for switching opioid from transdermal fentanyl to oral methadone in 17 patients with cancer. Reasons for switching were uncontrolled pain (41.1% of patients) and neurotoxic side effects (58.9% of patients). Methadone was initiated 8-24 hours after fentanyl withdrawal, depending on the patient's previous opioid doses (from < 100 microg per hour to > 300 microg per hour). The starting methadone dose was calculated according to a 2-step conversion between transdermal fentanyl:oral morphine (1:100 ratio) and oral morphine:oral methadone (5:1 ratio or 10:1 ratio). The correlation between previous fentanyl dose and the final methadone dose or the fentanyl:methadone dose ratio was assessed by means of Pearson and Spearman correlation coefficients (r), respectively. A Friedman test was used to compare pain intensity before and after the switch and the use of daily rescue doses.

RESULTS

Opioid rotation was fully or partially effective in 80% and 20%, respectively, of patients with somatic pain. Neuropathic pain was not affected by opioid switching. Delirium and myoclonus were reverted in 80% and 100% of patients, respectively, after opioid switching. A positive linear correlation was obtained between the fentanyl and methadone doses (Pearson r, 0.851). Previous fentanyl doses were not correlated with the final fentanyl:methadone dose ratios (Spearman r, - 0.327).

CONCLUSIONS

The protocol studied provided a safe approach for switching from transdermal fentanyl to oral methadone, improving the balance between analgesia and side effects in patients with cancer.

Dermal penetration of fentanyl: inter- and intraindividual variations

Fentanyl is a potent synthetic opioid that is increasingly being used in transdermal drug delivery systems. The target organ concentration of a drug administered dermally will depend on the rate of dermal absorption and the systemic elimination. We have studied the intra- and interindividual variation in dermal penetration of fentanyl in an in vitro model (static diffusion cells) with human skin, and compared the absorption of fentanyl from an aqueous solution with absorption from a commercial patch. The intraindividual variation in dermal penetration of fentanyl in aqueous solution was limited (18%) and no differences in penetration characteristics were observed between breast and abdominal skin. The interindividual variation in dermal penetration of fentanyl was extensive, with maximal fluxes ranging from 21-105 ng/cm2/hr following application of an infinite dose of fentanyl to the donor chamber. Use of transdermal drug delivery systems (patches) reduced the inter-individual variation. The permeability coefficients after application of fentanyl in aqueous solution and through patches were identical (0.0011 cm/hr). One person had a higher than average penetration rate following patch application, which may indicate that the human skin and not the patch barrier was the rate-determining factor for the other individuals included in this study.

Development and validation of a highly sensitive gas chromatographic–mass spectrometric screening method for the simultaneous determination of nanogram levels of fentanyl, sufentanil and alfentanil in air and surface contamination wipes

A highly sensitive gas chromatographic-mass spectrometric (GC-MS) analytical method for the determination of the opioid narcotics fentanyl, alfentanil, and sufentanil in industrial hygiene personal air samples and surface contamination wipes was developed and comprehensively validated. Sample preparation involved a single step extraction of the samples with methanol, fortified with a fixed amount of the penta-deuterated analogues of the opioid narcotics as internal standard. The GC-MS analytical procedure using selected ion monitoring (SIM) was shown to be highly selective. Linearity was shown for levels of extracted wipe and air samples corresponding to at least 0.1-2 times their surface contamination limit (SCL) and accordingly to 0.1-2 times their time weighted average occupational exposure limit (OEL-TWA) based on a full shift 9601 air sample. Extraction recoveries were determined for spiked air samples and surface wipes and were found to be quantitative for both sampling media in the entire range studied. The air sampling method's limit of detection (LOD) was determined to be 0.4 ng per sample for fentanyl and sufentanil and 1.6 ng per sample for alfentanil, corresponding to less than 1% of their individual OEL for a full shift air sample (9601). The limit of quantification (LOQ) was found to be 1.4, 1.2, and 5.0 ng per filter for fentanyl, sufentanil, and alfentanil, respectively. The wipe sampling method had LODs of 4 ng per wipe for fentanyl and sufentanil and 16 ng per wipe for alfentanil and LOQs of respectively, 14, 12, and 50 ng per wipe. The analytical intra-assay precision of the air sampling and wipe sampling method, defined as the coefficient of variation on the analytical result of six replicate spiked media was below 10 and 5%, respectively, for all opioids at all spike levels. Accuracy expressed as relative error was determined to be below 10%, except for alfentanil at the lowest spike level (-13.1%). The stability of the opioids during simulated air sampling was investigated. For fentanyl and sufentanil a quantitative recovery was observed at all spike levels, while for alfentanil recoveries ranged from 60.3 to 85.4%. When spiked air samples were stored at ambient temperature and at -15 degrees C quantitative recovery was found for fentanyl and sufentanil after 7 and 14 days. For alfentanil a slight loss seemed to occur upon storage during 7 days, being more explicit after 14 days. Ambient storage of spiked wipes seemed to lead to significant losses of all opioids studied, yielding recoveries of 37.7-88.3%. Upon storage of similar wipes at -15 degrees C a significantly higher recovery was found ranging from 77.3 to 88.3%. The developed analytical and sampling procedures have been recently applied in an explorative field study of which the results of surface contamination wipe sampling are presented in this paper. To our knowledge, this is the first study addressing the development and validation of analytical procedures for the assessment of external occupational exposure to potent opioid narcotics.

Highly sensitive gas chromatographic—mass spectrometric screening method for the determination of picogram levels of fentanyl, sufentanil and alfentanil and their major metabolites in urine of opioid exposed workers

Highly sensitive and specific analytical GC-MS procedures were developed and comprehensively validated for the determination of the opioid narcotics fentanyl, sufentanil and alfentanil and their major nor-metabolites in urine of potentially exposed opioid production workers. A simple, one step extraction protocol was developed using commercially available solid phase extraction (SPE) columns to recover all analytes from urine. The secondary amine functionalities of the nor-metabolites were derivatized to form stable, pentafluorobenzamide (PFBA)-derivatives with good chromatographic properties. Using the penta-deuterated analogues as internal standards, a limit-of-detection (LOD) of 2.5 pg fentanyl/ml, 2.5 pg sufentanil/ml and 7.5 pg alfentanil/ml urine was achieved. For the opioid metabolites the LODs were found to be <50 pg/ml urine. The developed analytical procedures show excellent intra-assay accuracy, particularly considering the ultra low levels of the analytes, with relative errors generally below 10%. Overall, an excellent reproducibility was observed with coefficients of variation below 10% at all spike levels for all opioid parent compounds and their metabolites, except for low norfentanyl concentrations. Upon storage at -30 degrees C urine samples were found to be stable for at least 2 months as no significant losses of either compound were observed. The developed analytical procedures have been successfully applied in a biological monitoring survey of fentanyl exposed production workers.

The effect of inhalant anesthetic and body temperature on peri-anesthetic serum concentrations of transdermally administered fentanyl in dogs

OBJECTIVES

To determine whether moderate hypothermia during anesthesia significantly affects the serum concentration of transdermally delivered fentanyl and whether halothane or isoflurane affect these concentrations.

STUDY DESIGN

Randomized cross-over experimental trial.

ANIMALS

Six mature, healthy Beagles (three males, three females) weighing 10.6 +/- 0.43 kg.

METHODS

A 50-microg hour(-1) fentanyl patch was applied 36 hours prior to anesthesia. Anesthesia was induced at time 0 (t = 0). Each dog received four treatments: isoflurane + normothermia (ISO-NORM), isoflurane + hypothermia (ISO-HYPO), halothane + normothermia (HAL-NORM), and halothane + hypothermia (HAL-HYPO). Dogs were intubated and maintained at 1.5 times MAC. Animals in the hypothermia treatments were cooled to 35 degrees C during anesthesia. Serum fentanyl analysis was performed at -36, -24, -12, 0, 0.5, 1, 1.5, 2, 2.5, 3, 3.5, 4, 4.5, 5, 6, 7, 8, 9, 10, 18, and 26 hours. Direct arterial blood pressures and arterial blood gases were monitored.

RESULTS

The mean body temperatures (+/-SEM) during the anesthetic period for the four treatments were: ISO-NORM = 37.7 +/- 0.07 degrees C, ISO-HYPO = 35.8 +/- 0.1 degrees C, HAL-NORM = 37.7 +/- 0.06 degrees C, and HAL-HYPO = 35.8 +/- 0.13 degrees C. The mean (+/-SEM) serum fentanyl concentrations (SFC) for both hypothermia treatments were significantly lower than baseline concentrations at t = 1 hour and persisted for the duration of anesthesia for the ISO-HYPO treatment but only from t = 1 to 2 hours for the HAL-HYPO treatment. Serum fentanyl concentrations returned to baseline within one hour of the end of anesthesia, regardless of body temperature. There were no significant differences between treatments for systolic or diastolic blood pressure but mean blood pressures were higher during normothermia versus hypothermia during the last hour of anesthesia.

CONCLUSIONS AND CLINICAL RELEVANCE

Hypothermia during inhalation anesthesia produced a significant reduction in SFC using transdermal administration and was more protracted with isoflurane than halothane anesthesia. While significant reductions in SFC occurred, the SFC were still within the range believed to confer analgesia.

Transdermal buprenorphine

Buprenorphine is a low molecular weight, lipophilic, opioid analgesic. Recently, a transdermal matrix patch formulation of buprenorphine has become available in three dosage strengths designed to release buprenorphine at 35, 52.5 and 70 micro g/h over a 72-hour period. At least satisfactory analgesia with minimal requirement for rescue medication (</=0.2 mg/day sublingual buprenorphine) was achieved by 34-50% of patients with chronic pain treated with transdermal buprenorphine 35, 52.5 or 70 micro g/h and 31% of placebo recipients, in one double-blind, placebo-controlled, randomised trial. In one trial involving patients unsuccessfully treated with weak opioids or morphine, 36.6% and 47.5% of buprenorphine 35 micro g/h and 52.5 micro g/h recipients, respectively, experienced at least satisfactory analgesia and received </=0.2 mg/day of sublingual buprenorphine compared with 16.2% of placebo recipients (both p </= 0.032). The requirement for rescue medication was reduced from baseline in >50% of patients treated with transdermal buprenorphine, in two trials. Furthermore, despite the availability of rescue medication to all patients, those receiving transdermal buprenorphine tended to experience greater pain relief, reduced pain intensity and longer pain-free sleep. Transdermal buprenorphine was generally well tolerated. Systemic adverse events were typical of opioid treatment or were attributable to the underlying disease.

Pain management of cancer patients with transdermal fentanyl: a study of 1828 step I, II, & III transfers

The aim of this observational study was to examine pain management outcomes and quality of life (QoL) measures in cancer patients with intolerable or chronic severe pain transferring from World Health Organization's step I, II, and III analgesics to the transdermal therapeutic fentanyl system (TTS-F). This study examines the safety and efficacy of TTS-F in long-term pain management, addressing the role of TTS-F in cancer pain. Pain measures were assessed in 1828 patients (step I [naïve], 268; step II [codeine], 1239; and step III [morphine], 321) on the basis of selected questions from the Greek-Brief Pain Inventory. Overall treatment satisfaction (scale, 1 to 4), QoL, and European Collaborative Oncology Group (ECOG) status were also recorded. These were assessed in relation to TTS-F dose, stratified by transfer step, primary cancer, metastases, type of pain, and concomitant use of anti-inflammatory drugs. Of 1828 patients, 100 (5.5%) withdrew, and an addition 14 (0.8%) discontinued because of side effects. A total of 1714 continued on study; 744 patients died, and 970 departed during the study period. In total, 93.8% were satisfied with their pain relief, and complete patient satisfaction was obtained within 2 months. Pain, QoL, and treatment satisfaction measures demonstrated statistically significant improvements over time, independent of the step transfer. Although doses of TTS-F were higher for step III > II > I and for metastatic than nonmetastatic, the median dose for all groups remained 50 microg/h throughout the study period. Pain and QoL improvements were independent of patient characteristic(s). Direct transfer to TTS-F for patients with intolerable or chronic moderate to severe cancer pain offers an efficient and safe long-term analgesic option for palliative care patients. Careful selection and follow-up by experienced palliative care specialists are mandatory. TTS-F as a first-line analgesic approach for severe cancer pain should be considered a viable option because of its durable efficacy and low incidences of side effects.

PERSPECTIVE

At a fairly constant dose of 50 microg/h, the transdermal therapeutic fentanyl system offers a safe, well-tolerated pain relief treatment for carefully monitored patients with cancer pain. The authors stress that this includes patients who experience difficulties in their pain management while progressing through the WHO's ladder for pain management.

The effect of rectal temperature on perianesthetic serum concentrations of transdermally administered fentanyl in cats anesthetized with isoflurane

OBJECTIVES

To determine whether moderate hypothermia during 4 hours of anesthesia with isoflurane substantially affects serum concentrations of transdermally administered fentanyl in the perianesthetic period in cats.

ANIMALS

7 healthy mature cats.

PROCEDURE

A fentanyl patch (25 microg/h) was applied to the shaved thorax 24 hours before induction of anesthesia. Anesthesia was induced at time 0. Each cat received 2 treatments in a random order. Treatments were isoflurane anesthesia with normothermia and isoflurane anesthesia with hypothermia. Cats were intubated, connected to a nonrebreathing circuit, and maintained at 1.3X minimum alveolar concentration for 4 hours. Cats in the hypothermia treatment groups were actively cooled to 35 degrees C following the induction of anesthesia. Serum fentanyl analysis was performed at -24, -12, 0, 1, 2, 3, 4, 4.5, 5, 6, 7, 8, 9, 10, 12, and 24 hours.

RESULTS

Mean +/- SEM serum fentanyl concentration (SFC) for the hypothermia treatment group (0.598 +/- 0.3048 ng/mL) was significantly lower than the baseline concentration (1.834 +/- 0.6393 ng/mL) at 1 hour. This significant reduction persisted for the duration of anesthesia for the hypothermia treatment group. Serum fentanyl concentrations returned to baseline values within 1 hour of the end of anesthesia, regardless of body temperature.

CONCLUSIONS AND CLINICAL RELEVANCE

Hypothermia during inhalant anesthesia induced a significant reduction in SFC obtained with transdermal administration. The impact of this reduction in SFC on the contribution of transdermally administered fentanyl to any reduction in the need for inhalant anesthesia remains to be determined.

Transdermal fentanyl: informed prescribing is essential

While morphine is historically the gold standard for the management of severe cancer pain, some patients either do not achieve adequate analgesia, or suffer intolerable side-effects. For these patients an alternative opioid is recommended. One such alternative is the potent mu opioid agonist fentanyl, delivered in a transdermal controlled release formulation. Similar to morphine, transdermal fentanyl is effective for the management of moderate to severe cancer pain. However, inappropriate prescribing of transdermal fentanyl, particularly in the clinical setting of unstable pain, can cause significant opioid toxicity, as highlighted in the case reports described.

Long-term cancer pain management in morphine pre-treated and opioid naive patients with transdermal fentanyl

There is emerging data supporting the use of TTS-F (transdermal therapeutic system-fentanyl) in opioid naive patients. Our study examines the safety and efficacy of TTS-F in the long-term control of cancer pain in opioid naive patients and those transferring from oral morphine. Pain was assessed in 589 patients (Group A: 268 opioid naive, Group B: 321 transferring from morphine) using a Visual Analogue Scale (VAS; 0-10), based on selected questions from the Greek Brief Pain Inventory (GBPI). Overall treatment satisfaction was assessed on a 4-point scale. Quality of Life (QOL) and ECOG (0-4) status were also recorded. These were assessed in relation to TTS-F dose, pain type (neuropathic, combined, nociceptive), concomitant use of anti-inflammatory drugs and other demographic data. Of 589 patients, 59 (10%) withdrew as a result of inadequate pain satisfaction or for other reasons. There were no discontinuations due to side effects; no Grade 3-4 events occurred. A total of 530 continued on-study, 211 patients died during study period and 295 departed; all (506; 89%) were satisfied with their pain relief. Analysis of patients at baseline, 28 days, 6 and 12 month time points (n = 153 Group A; n = 214 Group B) with respect to QOL and pain measures indicated a statistically significant (p < 0.001) improvement in all measures across time independent of pain type, or any other patient characteristic(s). In patients with intolerable pain, transfer to TTS-F offers an efficient and safe long-term analgesic option. TTS-F offers durable long-term maintenance of pain relief with acceptable side effects in opioid naive patients. In general, TTS-F as a first line analgesic approach for carefully selected and monitored patients experiencing moderate to severe cancer pain should be considered.

The use of long-acting opioids in chronic pain management

The consensus statement from the American Pain Society and American Academy of Pain Medicine states that the undertreatment of pain is unjustified [6]. It has been suggested that opioid therapy can be used effectively to treat noncancer pain in a subset of patients [26], and this is becoming more acceptable [3]. Providing sustained analgesia is an important aspect of therapy, and medications should be administered on an around-the-clock basis, because regular administration of doses maintains a constant level of drug in the body and helps prevent recurrence of pain. Ideal treatment for persistent pain is a long-acting opioid administered around the clock to prevent baseline pain, with the use of short-acting opioids as supplemental agents for breakthrough pain. Controlled-release formulations can lessen the inconvenience associated with around-the-clock administration of short-acting opioids. Sustained analgesia also can be achieved with transdermal fentanyl, which combines a strong opioid with a 72-hour release profile and the benefits of a parenteral route, avoiding first-pass metabolism. Controlled-release formulations of morphine and oxycodone are available in the United States, and hydromorphone preparations are being reviewed for approval. Clinical experience with these formulations and transdermal fentanyl indicates that these agents are equally effective in controlling pain. Studies have demonstrated improved quality of life with the transdermal route and with controlled-release morphine and oxycodone. Because of patch reapplication every 72 hours, the transdermal route also enhances compliance. Use of an opioid without the need for oral or intravenous administration and the opportunity to improve compliance are among the advantages of the transdermal route in clinical practice. The nurse has an important role in the management of patients receiving long-acting opioids for chronic noncancer pain, Facilitation of the conversion from short-acting to long-acting opioids may be the initial step. Individualization of therapy to determine which route and product best suits the patient's needs and lifestyle can be accomplished through a comprehensive nursing assessment. Titration of dose along with institution of a short-acting opioid for break-through pain may require frequent interventions that a nurse familiar with the patient can provide. Prevention and management of opioid-related adverse events are essential for effective opioid therapy. Providing patient and family education regarding administration, monitoring, and management of opioid therapy is an important nursing role. Lastly, documentation of pain level, functional status, and opioid-related adverse events is required for each contact with the patient, to make this information available to all who assist in the management of the patient's pain. Chronic noncancer pain is an experience that affects all aspects of a patient's life. Effective pain management with long-acting opioids may help the patient to focus on the positive aspects of life, decreasing the focus on pain.

Management of Painful Conditions in the Elderly

Persistent pain conditions in the elderly are most often due to degenerative disorders of the spine, osteoarthritis of the joints, malignant cancer, and vascular disorders. The consequences of persistent pain include depression, anxiety, de-creased socialization, sleep disturbance, impaired ambulation, and increased healthcare utilization. Proper pain assessment is the key to selecting appropriate treatment. Barriers to pain assessment are associated with the patient's perception of pain and the caregiver's attitude towards providing effective treatment. All elderly patients have age-related physiologic changes that affect absorption, distribution, metabolism, and clearance of medications used for pharmacologic treatment. Medications used in pain management include opioids, nonsteroidal anti-inflammatory drugs, gabapentin, nortriptylline, desipramine, and lidocaine 5%patch. Pharmacists have an important role in the monitoring of medications in elderly. As the utilization of prescription medication continues to increase in the elderly, pharmacists are becoming the frontline of healthcare care for this population.