Transdermal buprenorphine

Buprenorphine TTS for children--a review of the drug's clinical pharmacology

OBJECTIVE

The transdermal therapeutic system (TTS) with buprenorphine is currently being used 'off-label' to treat chronic pediatric pain. We compiled available pharmacokinetic (PK), pharmacodynamic (PD), and clinical pediatric data on buprenorphine to rationalize treatment regimens.

METHODS

We conducted a systematic biomedical literature review focusing on pediatric buprenorphine data.

RESULTS

There are few relevant pediatric buprenorphine data, particularly in children suffering chronic pain. There are no pediatric PK and PD data for children with chronic pain given sublingual or TTS formulations. Children given single dose buprenorphine have increased drug clearance referenced to bodyweight with a possible paradoxical longer duration of action. Buprenorphine metabolism is independent of renal function, which is advantageous in renal insufficiency. The risk of respiratory depression after buprenorphine is difficult to quantify. A concentration-response relationship for respiratory effects has not been described and it is unknown whether children have a ceiling effect similar to that described in healthy adult volunteers.

CONCLUSIONS

Buprenorphine is of interest in pediatric postoperative pain and cancer pain control because of its multiple administration routes, long duration of action, and metabolism largely independent of renal function. There is little reason to expect buprenorphine effects in children out of infancy are fundamentally different to those in adults. From the limited pediatric data available, it appears that buprenorphine has no higher adverse potential than the more commonly used opioids. There is an urgent need for focused PK, PD, and safety studies in children before use in children becomes more widespread.

Transdermal Opioids for Cancer Pain Management

The prevalence of pain in cancer is up to 90%, more than 45% of this can be adequately managed using the World Health Organisation three step analgesic ladder.Transdermal opioids are safe, effective, and produce significantly fewer side effects than oral morphine when used for moderate to severe cancer pain.Transdermal buprenorphine has a lower incidence of systemic side effects than transdermal fentanyl and it is indicated for use in cancer patients with neuropathic pain and renal dysfunction.Transdermal opioids require a long lag period for dose stabilisation and elimination, hence are unsuitable for acute or unstable pain, and may result in prolonged side effects.Transdermal analgesics reduce the need for frequent dosing, clock watching and are more convenient for patients, physicians and carers, hence increasing treatment compliance.

Skin permeation of buprenorphine and its ester prodrugs from lipid nanoparticles: lipid emulsion, nanostructured lipid carriers and solid lipid nanoparticles

The aim of this study was to develop and characterize lipid nanoparticle systems for the transdermal delivery of buprenorphine and its prodrugs. A panel of three buprenorphine prodrugs with ester chains of various lengths was synthesized and characterized by solubility, capacity factor (log K'), partitioning between lipids and water and the ability to penetrate nude mouse skin. Colloidal systems made of squalene (lipid emulsion, LE), squalene + Precirol (nanostructured lipid carriers, NLC) and Precirol (solid lipid nanoparticles, SLN) as the lipid core material were prepared. Differential scanning calorimetry showed that the SLN had a more-ordered crystalline lattice in the inner matrix compared to the NLC. The particle size ranged from 220-300 nm, with NLC showing the smallest size. All prodrugs were highly lipophilic and chemically stable, but enzymatically unstable in skin homogenate and plasma. The in vitro permeation results exhibited a lower skin delivery of drug/prodrug with an increase in the alkyl chain length. SLN produced the highest drug/prodrug permeation, followed by the NLC and LE. A small inter-subject variation was also observed with SLN carriers. SLN with soybean phosphatidylcholine (SLN-PC) as the lipophilic emulsifier showed a higher drug/prodrug delivery across the skin compared to SLN with Myverol, a palmitinic acid monoglyceride. The in vitro permeation of the prodrugs occurred in a sustained manner for SLN-PC. The skin permeation of buprenorphine could be adjusted within a wide range by combining a prodrug strategy and lipid nanoparticles.

Managing severe cancer pain: the role of transdermal buprenorphine: a systematic review

Pain is a frequent and important symptom in cancer patients. Among the available strong opioids, transdermal buprenorphine has been licensed in Europe since 2002, and results from a few clinical studies suggest that it may be a good alternative to the other oral or transdermal opioids. To assess the best available evidence on its efficacy and safety, we carried out a systematic literature review with the aim of pooling relevant studies. We identified 19 eligible papers describing 12 clinical studies (6 randomized controlled trials and 6 observational prospective studies), including a total of about 5000 cancer patients. Given the poor quality of reports and the heterogeneity of methods and outcomes, pooling was not feasible as the type of data was not appropriate for combining the results statistically. A meta-analysis based on individual data is ongoing in the context of the Cochrane Collaboration. In conclusion, although the narrative appraisal of each study suggests a positive risk benefit profile, well designed and statistically powered controlled clinical trials are needed to confirm this preliminary evidence.

Pediatric palliative care: use of opioids for the management of pain

Pediatric palliative care (PPC) is provided to children experiencing life-limiting diseases (LLD) or life-threatening diseases (LTD). Sixty to 90% of children with LLD/LTD undergoing PPC receive opioids at the end of life. Analgesia is often insufficient. Reasons include a lack of knowledge concerning opioid prescribing and adjustment of opioid dose to changing requirements. The choice of first-line opioid is based on scientific evidence, pain pathophysiology, and available administration modes. Doses are calculated on a bodyweight basis up to a maximum absolute starting dose. Morphine remains the gold standard starting opioid in PPC. Long-term opioid choice and dose administration is determined by the pathology, analgesic effectiveness, and adverse effect profile. Slow-release oral morphine remains the dominant formulation for long-term use in PPC with hydromorphone slow-release preparations being the first rotation opioid when morphine shows severe adverse effects. The recently introduced fentanyl transdermal therapeutic system with a drug-release rate of 12.5 microg/hour matches the lower dose requirements of pediatric cancer pain control. Its use may be associated with less constipation compared with morphine use. Though oral transmucosal fentanyl citrate has reduced bioavailability (25%), it inherits potential for breakthrough pain management. However, the gold standard breakthrough opioid remains immediate-release morphine. Buprenorphine is of special clinical interest as a result of its different administration routes, long duration of action, and metabolism largely independent of renal function. Antihyperalgesic effects, induced through antagonism at the kappa-receptor, may contribute to its effectiveness in neuropathic pain. Methadone also has a long elimination half-life (19 [SD 14] hours) and NMDA receptor activity although dose administration is complicated by highly variable morphine equianalgesic equivalence (1 : 2.5-20). Opioid rotation to methadone requires special protocols that take this into account. Strategies to minimize adverse effects of long-term opioid treatment include dose reduction, symptomatic therapy, opioid rotation, and administration route change. Patient- or nurse-controlled analgesia devices are useful when pain is rapidly changing, or in terminal care where analgesic requirements may escalate. In this article, we present detailed pediatric pharmacokinetic and pharmacodynamic data for opioids, their indications and contraindications, as well as dose-administration regimens that include practical strategies for opioid switching and dose reduction. Additionally, we discuss the problem of hyperalgesia and the use of adjuvant drugs to support opioid therapy.

Short- and intermediate-term efficacy of buprenorphine TDS in chronic painful neuropathies

Buprenorphine is a potent opioid available as a transdermal delivery system (TDS) formulation. This open-label study investigated its safety, tolerability, and efficacy in 30 patients with chronic painful neuropathy. Subjects with visual analogue scale (VAS) score > or = 5 under stable analgesic treatment were entered. The starting dosage of 35 microg/h was increased up to 70.0 microg/h in case of unsatisfactory pain control as assessed by fortnightly visits. The primary endpoint was the number of patients achieving at least 30% pain relief at day 42 visit. Treatment was safe over the study period. Nine patients dropped out for side effects, mostly nausea and daily sleepiness. Buprenorphine TDS was well tolerated in 21 patients. Thirteen patients achieved > 30% of pain relief at day 42 visit. Five patients needed to increase the dosage to 52.5 microg/h. Eight patients did not meet the primary outcome, but none allowed increasing the dosage to 70 microg/h, and four patients withdrew consent to continue the study before day 42 visit because of a 'fear to become addicted,' although 40% had obtained VAS reduction. In our study, which needs to be confirmed by a controlled trial, buprenorphine TDS induced clinically meaningful pain relief in about 40% of patients with chronic painful neuropathy, suggesting its use as a third-line treatment.

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.

Treatment of ischemic pain in patients suffering from peripheral vasculopathy with transdermal buprenorphine plus epidural morphine with ropivacaine vs. epidural morphine with ropivacaine

AIM

This study compared the efficacy and safety of buprenorphine transdermal delivery system with peridural infusion of morphine and ropivacaine to peridural infusion alone for the control of ischemic pain in patients suffering from peripheral vasculopathy.

METHODS

Eighty-six patients were randomized into two groups. In the first group, a buprenorphine patch 35 microg/hour TTDS (transtec transdermal device plus ropivacaine and morphine) was applied, and a peridural infusion of ropivacaine/morphine (200 mg + 2 mg) was established. In the second group, ropivacaine and morphine analgesia was obtained using a peridural infusion and a placebo patch. The primary efficacy parameter was the visual analog scale score for pain. Secondary parameters of efficacy were the short-form McGill Pain Questionnaire scores and a score for pain interference with sleep obtained from patient diaries evaluated every week for a period of 4 weeks.

RESULTS

Subjects in the TTDS group reported a reduction in pain, increased sleep, and a lower incidence of side effects compared with the control group.

CONCLUSION

Transdermal buprenorphine use resulted in significant pain relief with excellent patient satisfaction, which may translate into improvement in mood and quality of life.

Assessing cognitive and psychomotor performance under long-term treatment with transdermal buprenorphine in chronic noncancer pain patients

BACKGROUND

The therapeutic use of opioids has been associated with altered cognition and impaired psychomotor function. Several studies have demonstrated the impact of opioid therapy on psychomotor performance and cognition, but there are no data about the effect of long-term treatment with transdermal buprenorphine on driving ability.

METHODS

Thirty patients suffering from chronic noncancer pain, who had been treated with stable doses of transdermal buprenorphine, included in a prospective trial and compared with 90 healthy volunteers (matched pairs). A computerized test battery, developed to assess the driving ability of traffic delinquents in Germany, was used. Attention reaction, visual orientation, motor coordination, and vigilance were evaluated. The data from 14 variables were assessed, and for each test, a relevant score was defined. As the primary end-point, the sum score of the three relevant scores was determined. A weaker statistical means to assess the patient's performance is to compare the test results to an age-independent control group. Individuals performing worse than the 16th percentile of this control group are considered to be unable to drive according to German law.

RESULTS

According to tests that predict driving ability, patients receiving transdermal buprenorphine were shown to be noninferior to the control group. Driving ability, as defined as a result above the 16th percentile, did not differ significantly between the patients and the control group.

CONCLUSION

Long-term use of transdermal buprenorphine for chronic noncancer pain does not impair driving ability, but because of the individual variability of test results, an individual assessment is recommended.

Buprenorphine ameliorates the effect of surgery on hypothalamus-pituitary-adrenal axis, natural killer cell activity and metastatic colonization in rats in comparison with morphine or fentanyl treatment

Not all opioids employed in clinical practice share the same immunosuppressive properties. The potent partial micro-agonist buprenorphine appears to exhibit a neutral effect on the immune responses. Surgery stress is associated with decreased natural killer cell activity (NK) and enhancement of tumor metastasis in rats. We analyzed the ability of buprenorphine to prevent the effects of experimental surgery on HPA activation (plasma corticosterone levels), NK activity and lung diffusion of the NK sensitive tumor MADB106. Buprenorphine (0.1mg/kg) was compared with equianalgesic doses of fentanyl (0.1mg/kg) and morphine (10mg/kg) in this animal model. In normal animals morphine and fentanyl stimulate the HPA axis, decrease NK activity and augment tumor metastasis, while buprenorphine is devoid of these effects. Surgery significantly raised corticosterone levels, suppressed NK activity and increased MADB106 metastasis. Only buprenorphine was able to prevent the neuroendocrine and immune system alterations and ameliorate the increase of tumor metastasis induced by surgical stress. These preclinical findings suggest that an adequate treatment of surgically induced stress immunosuppression with an opioid drug devoid of immunosuppressive effects may also play a protective role against the metastatic diffusion following cancer surgery.

Rational Use of Sublingual Opioids in Palliative Medicine

The sublingual administration of opioid analgesics has been a mainstay in the pain management of homebound dying hospice patients who are no longer able to swallow. It is also a potentially useful route of administration in other situations in which the oral route is not available and other routes are impractical or inappropriate. Potential advantages of the sublingual route include rapid analgesic onset and avoidance of hepatic first-pass metabolism. Pharmacokinetic and pharmacodynamic studies have yielded widely disparate data on sublingual morphine. Other opioids have been less studied. Available data suggests limited sublingual availability of hydrophilic opioids (e.g., morphine, oxycodone, and hydromorphone) and superior absorption of the lipophilic opioids (e.g., methadone and the fentanils). Buprenorphine, a potent, lipophilic, partial mu-opioid receptor agonist, appears promising but awaits further study.

Efectividad y seguridad de la buprenorfina transdérmica en el tratamiento del dolor crónico en el anciano: estudio de postautorización observacional y prospectivo

BACKGROUND AND OBJECTIVE

A number of subjects aged over 65 suffer from some kind of chronic pain. The constant growth of this demographic group makes research of new and efficacious treatment strategies necessary. Transdermal buprenorphine has shown to be a safe and efficacious pharmacotherapy for patients with moderate to severe chronic pain in clinical trials. This paper provides the outcome of this drug in routine clinical practice.

PATIENTS AND METHOD

A prospective, uncontrolled observational study that included a 3-month follow-up of patients starting transdermal buprenorphine was performed. Information was collected systematically on pain relief, quality of life (EuroQol-5D questionnaire), comfort of patch use and adverse events. Missing data were imputed by the <<worst case>>.

RESULTS

Out of 1,188 patients with known age, 564 were under 65, 337 were between 65 and 75, and 287 were over 75 years. Within these respective age groups, 63.9%, 66.3% and 67.7% of patients showed <<good>> or <<very good>> pain relief; 60.4%, 60.7% and 65.2% showed improvement of sleep quality; and the mean increases of the score of the EuroQol-5D visual analogue scale were 16.0 mm, 15.8 mm and 16.8 mm. Drug-related adverse events were reported in 39.6%, 35.4% and 31.9% of patients, respectively.

CONCLUSIONS

This study performed in the routine-care setting supports the findings from previous randomised controlled clinical trials of transdermal buprenorphine.

Transdermal buprenorphine in pain management--experiences from clinical practice: Five case studies

Buprenorphine is a semi-synthetic opioid derived from thebaine. The transdermal formulation of buprenorphine has been available in Belgium for 3 years, during which time the Pain Clinic of the St Elisabeth of Verviers Hospital has gained experience in the use of transdermal buprenorphine for the treatment of moderate-to-severe pain. This paper presents four cases of chronic, non-malignant pain, and one case of chronic cancer pain. By starting patients on low doses and slowly titrating upwards, transdermal buprenorphine matrix patches provided effective analgesia and were well tolerated. Low doses of transdermal buprenorphine were created by cutting the smallest available matrix patch (35 mug/h) into halves or quarters. The initial dose was then gradually titrated upwards to the dose needed for optimum pain relief by the patients. No problems were encountered in switching patients from prior analgesic therapy with other opioids to transdermal buprenorphine.

Transdermal buprenorphine in the treatment of chronic pain

The transdermal matrix patch formulation of buprenorphine has been shown to be effective in managing moderate-to-severe cancer pain and severe pain unresponsive to nonopioid analgesics. Clinical trials have revealed that it is possible to switch from weak opioids or low doses of step III opioids to transdermal buprenorphine without any problems. With buprenorphine patches, the sublingual buprenorphine intake was dose-dependently reduced and was superior to placebo in this respect. The proportion of responders increased with the buprenorphine dose, and a higher proportion of patients receiving buprenorphine patches reported uninterrupted sleep for longer than 6 h compared with those receiving placebo. In a long-term, open, follow-up study in which the mean duration of treatment was 7.5 months, analgesia was rated as at least satisfactory by 90% of patients. Almost 60% of patients could manage their pain with one patch alone or with one additional sublingual tablet a day during the whole period of treatment, indicating a low incidence of tolerance development. The buprenorphine transdermal patch was assessed as user friendly by 94.6% of patients. In a postmarketing surveillance study, pain relief with transdermal buprenorphine was rated as good or very good by 70% of the responders. Postmarketing surveillance studies have shown that transdermal buprenorphine is also effective in the management of nociceptive and neuropathic pain, which some studies have shown to be relatively insensitive to mu-opioid analgesics, such as morphine. Transdermal buprenorphine was well tolerated. Most adverse events were either local reactions to the patch that generally subsided within 24 h or systemic events typical of treatment with opioid analgesics, such as nausea, vomiting and constipation.

Transdermal opioids for cancer pain

Patients with moderate to severe malignancy-related pain frequently require the use of opioid pharmacotherapy. Unfortunately, many cancer patients continue to be prescribed subtherapeutic doses of pain medications resulting in undo suffering and diminished quality of life. The choice of analgesic pharmacotherapy should be individualized and based on the intensity and etiology of pain reported by the patient. Health care providers must be able to readily quantify the relative analgesic potency when converting from one opioid to another or from one route of administration to another. Transdermal fentanyl is effective and well tolerated pharmacotherapy for the cancer pain patients. However, clinicians need to be cognizant that the U.S./U.K. manufacturer's recommendations for equilalagesic dosing of transdermal fentanyl may result in initial doses that produce subtherapeutic levels and unrelieved pain in some patients. A more aggressive dosing algorithm for transdermal fentanyl using a 2:1 (mg/day of oral morphine: mcg/hr of transdermal fentanyl) conversion ratio that considers both a review of the literature and clinical experience should help clinicians individualize cancer pain pharmacotherapy. Transdermal buprenorphine is now being prescribed in Europe and Australia for chronic and cancer pain management. Buprenorphine's mixed agonist/antagonist activity, dosage ceiling, and high affinity to the opiate receptor limits its use to those patients who do not already require large daily doses of opioids. Thus, buprenorphine may not be an appropriate medication for some patients with advanced unremitting cancer pain.

Opioids in pain management of blood-related malignancies

Opioids are basic analgesics used in the treatment of moderate to severe pain in patients affected by blood-related malignancies. They should be sequentially administered according to the World Health Organisation scale for cancer pain. Initial treatment and titration with opioids should be based on immediate-release preparations, to be administered at appropriate intervals in order to relieve pain and to satisfy the individual opioid requirement. Once a relatively good pain control has been achieved, a slow release formulation at equivalent doses can be given. Most patients can be adequately managed using oral formulation opioids. However, a small group, such as those presenting severe mucositis or requiring a rapid pain relief, should be managed by intravenous continuous infusion and/or by a patient-controlled analgesia system; while for patients in the community, there are distinct advantages to using the subcutaneous route. Other available routes of administration for opioids, can be used in selected circumstances, including rectal, transdermal, epidural, intrathecal and intramuscular. The invasive neuraxial route has a very limited role in patients with haematological malignancies, given the high risk of infection and bleeding. Through a close observation and a careful management, opioid-related side effects can be effectively prevented and treated. This article reviews the principles of opioid therapy and how opioids can be adapted for patients with pain due to haematological malignancies.

Pharmacokinetics of a Lidocaine Patch 5% in Dogs

Lidocaine is increasingly used in transdermal drug delivery systems for different pain conditions in human medicine whereby several pharmacokinetic studies have demonstrated minimal systemic absorption in men. In the present study, the pharmacokinetics of a lidocaine patch 5% was studied in six dogs. In the first experiment, one single lidocaine patch was applied for 12 h to the lateral side of the thorax after removing the hair either by clipping or by the application of a depilatory agent, according to a two-way crossover design. No potential adverse effects induced by the patches were observed in either group. In dogs with clipped hair, a mean peak plasma lidocaine concentration of 62.94 ng/ml was obtained after 10.67 h. In the depilatory group, a mean peak plasma concentration of 103.55 ng/ml was reached after 9.27 h. Significant differences in the AUC(0 --> infinity), C(max), k(a) and T(1/2a) were noticed between the two groups. No significant differences were found for the elimination parameters and for T(max). In the second experiment, the patches were applied for 60 h to the clipped skin in order to study the absorption kinetics after a prolonged application period. There, the mean peak lidocaine plasma concentration was 45.18 ng/ml achieved after 24 h and a final concentration of 29.37 ng/ml was obtained at 60 h. In conclusion, all dogs tolerated the transdermal lidocaine patch well. The results of this study suggest that there is an overall minimal absorption from the lidocaine patch. However, the application of a depilatory agent leads to a more rapid and increased absorption of lidocaine.

Enhancement of transdermal fentanyl and buprenorphine antinociception by transdermal Δ9-tetrahydrocannabinol

Previous studies have demonstrated that delta9-tetrahydrocannabinol (THC) enhances the antinociceptive potency of many opioids administered by a variety of different routes of administration. We hypothesized that THC would enhance fentanyl or buprenorphine analgesia via the transdermal route of administration. THC was first demonstrated to enhance opioid antinociception when both drugs were administered parenterally in a hairless guinea pig model using the pin prick test. A low dose of THC (50 mg/kg, i.p.) produced no antinociception. However, THC enhanced the potency of s.c. fentanyl by 6.7-fold, and s.c. buprenorphine in a non-parallel fashion. For the transdermal studies, THC, fentanyl or buprenorphine was applied by pipette to the skin of the dorsum between the fore- and hind-flanks and covered with individual Tegederm patches. THC (400 mg/kg) produced no antinociception. However, THC enhanced fentanyl's potency by 3.7-fold at 2-h, and 5.8-fold at 4-h. Buprenophine's potency was increased 8.2-fold at 2-h and 7.2-fold at 4-h when co-administered with THC. These results indicate that the enhancement of transdermal opioids by THC could lead to the design of an effective combination analgesic patch.

Buprenorphine in cancer pain

Buprenorphine is a broad spectrum, highly lipophilic, and long-acting partial mu opioid receptor agonist that is noncross tolerant to other opioids. Buprenorphine can be given by several routes. Metabolism is through CYP3A4 and CYP2C8 and by conjugases. Constipation and sexual dysfunction appear to be less with buprenorphine than with other opioids. The recent development of a polymer matrix patch delivery system for buprenorphine prevents "dose dumping" and facilitates pain management in those unable to take oral analgesics. Sublingual buprenorphine has been combined with naloxone to prevent illicit conversion to parenteral administration. Buprenorphine has been used extensively to control cancer pain. In certain clinical situations, buprenorphine may have particular advantages over other opioids.

Comparison of the respiratory effects of intravenous buprenorphine and fentanyl in humans and rats

BACKGROUND

There is evidence from animal studies suggesting the existence of a ceiling effect for buprenorphine-induced respiratory depression. To study whether an apparent ceiling effect exists for respiratory depression induced by buprenorphine, we compared the respiratory effects of buprenorphine and fentanyl in humans and rats.

METHODS

In healthy volunteers, the opioids were infused i.v. over 90 s and measurements of minute ventilation at a fixed end-tidal PCO2 of 7 kPa were obtained for 7 h. Buprenorphine doses were 0.7, 1.4, 4.3 and 8.6 microg kg(-1) (n=20 subjects) and fentanyl doses 1.1, 2.1, 2.9, 4.3 and 7.1 microg kg(-1) (n=21). Seven subjects received placebo. In rats, both opioids were infused i.v. over 20 min, and arterial PCO2 was measured 5, 10, 15 and 20 min after the start of fentanyl infusion and 30, 150, 270 and 390 min after the start of buprenorphine infusion. Doses tested were buprenorphine 0, 100, 300, 1000 and 3000 microg kg(-1) and fentanyl 0, 50, 68 and 90 microg kg(-1).

RESULTS

In humans, fentanyl produced a dose-dependent depression of minute ventilation with apnoea at doses > or = 2.9 microg kg(-1); buprenorphine caused depression of minute ventilation which levelled off at doses > or = 3.0 microg kg(-1) to about 50% of baseline. In rats, the relationship of arterial PCO2 and fentanyl dose was linear, with maximum respiratory depression at 20 min (maximum PaCO2 8.0 kPa). Irrespective of the time at which measurements were obtained, buprenorphine showed a non-linear effect on PaCO2, with a ceiling effect at doses > 1.4 microg kg(-1). The effect on PaCO2 was modest (maximum value measured, 5.5 kPa).

CONCLUSIONS

Our data confirm a ceiling effect of buprenorphine but not fentanyl with respect to respiratory depression.

Practice guidelines for transdermal opioids in malignant pain

Patients with moderate-to-severe malignancy-related pain require opioid pharmacotherapy. Many cancer patients continue to be prescribed subtherapeutic doses of pain medications resulting in undue suffering and diminished quality of life. Pain associated with malignancy and its treatment may exacerbate other symptoms associated with cancer, including nausea, fatigue, weakness, dyspnoea, constipation and impaired cognition. The choice of analgesic pharmacotherapy should be individualised and based on the intensity of pain reported by the patient, rather than its specific aetiology. When selecting pain management pharmacotherapy, the healthcare provider should consider the patient's pain level, activity level and any comorbid illness. Intolerable adverse effects, ineffective pain relief or a change in the patient's clinical status can dictate the need for a new pain management regimen. Healthcare providers must be able to readily quantify the relative analgesic potency when converting from one opioid to another or from one route of administration to another. Transdermal formulations of fentanyl and buprenorphine are effective pharmacotherapy that can be safely used for cancer patients with pain. However, clinicians need to be cognisant that the US/UK manufacturer's recommendations for equianalgesic dose administration of transdermal fentanyl may result in initial doses that produce subtherapeutic concentrations and unrelieved pain in some patients. A less conservative dose administration algorithm for transdermal fentanyl using a 2:1 (mg/day of oral morphine : microg/h of transdermal fentanyl) conversion ratio that considers both a review of the literature and clinical experience should help clinicians individualise cancer pain pharmacotherapy.

Broad analgesic profile of buprenorphine in rodent models of acute and chronic pain

Buprenorphine is a potent opioid analgesic clinically used to treat moderate to severe pain. The present study assessed its analgesic efficacy in a broad range of rodent models of acute and chronic pain. In the phenylquinone writhing, hot plate, and tail flick mouse models of acute pain, full analgesic efficacy was obtained (ED50 values: 0.0084-0.16 mg/kg i.v.). Full analgesic efficacy was also obtained in yeast- and formalin-induced inflammatory pain (ED50 values: 0.0024-0.025 mg/kg i.v., rats and mice) and in mustard-oil-induced spontaneous pain, referred allodynia, and referred hyperalgesia in mice (ED50 values: 0.018-0.025 mg/kg i.v.). Buprenorphine strongly inhibited mechanical and cold allodynia in mononeuropathic rats, as well as mechanical hyperalgesia and cold allodynia in polyneuropathic rats (ED50 values: 0.055 and 0.036 mg/kg i.v. and 0.129 and 0.038 mg/kg i.p., respectively). It is concluded that buprenorphine shows a broad analgesic profile and offers the opportunity to treat different pain conditions, including neuropathic pain.

Transdermal buprenorphine in the treatment of chronic pain: Resultsof a phase III, multicenter, randomized, double-blind, placebo-controlled study

BACKGROUND

Buprenorphine, a potent opioid analgesic, has been available in parenteral and oral or sublingual(SL) formulations for >25 years. In 2001, the buprenorphine transdermal delivery system (TES) was introduced at 3 release rates (35, 52.5, and 70 microg/h) for the treatment of chronic cancer and noncancer pain.

OBJECTIVE

This study compared the analgesic efficacy and tolerability of buprenorphine TES at a release rate of 35 microg/h with those of buprenorphine SL and placebo in patients with severe or very severe chronic cancer or noncancer pain.

METHODS

This multicenter, double-blind, placebo-controlled, parallel-group trial was 1 of 3 Phase III studies involved in the clinical development of buprenorphine TDS. It comprised a 6-day open-label run-in phase in which patients received buprenorphine SL 0.8 to 1.6 mg/d as needed and a double-blind phase in which patients were randomized to receive 3 sequential patches containing buprenorphine TES 35 microg/h or placebo, each lasting 72 hours. Rescue analgesia consisting of buprenorphine SL 02-mg tablets was available as needed throughout the double-blind phase. The main outcome measures were (1) the number of buprenorphine SL tablets required in addition to buprenorphine TES during the double-blind phase compared with the placebo group and compared with the buprenorphine SL requirement during the run-in phase, and (2) patients' assessments of pain intensity, pain relief, and duration of sleep uninterrupted by pain in the double-blind phase compared with the run-in phase. Adverse events were documented throughout the study.

RESULTS

One hundred thirty-seven patients were included in the double-blind phase (90 buprenorphine TES, 47 placebo). The buprenorphine TES group included 47 men and 43 women (mean [SD] age, 56.0 [12.1] years), and the placebo group included 23 men and 24 women (mean age, 55.7 [12.9] years). Forty-five patients had cancer-related pain and 92 had noncancer-related pain. The 2 treatment groups were comparable with respect to sex distribution, age, height, and body weight Patients receiving buprenorphine TES significantly reduced their consumption of buprenorphine SL tablets in the double-blind phase compared with patients receiving placebo (reduction of 0.6 [0.4] mg vs 0.4 [0.4] mg; P = 0.03). The relationship between the buprenorphine SL dose in the run-in phase and the number of buprenorphine SL tablets required in the double-blind phase was dose dependent in the active-treatment group only. Patients' assessments of pain intensity and pain relief suggested better analgesia with buprenorphine TES than with placebo, although the differences did not reach statistical significance. The proportion of patients who reported sleeping for >6 hours uninterrupted by pain in the double-blind phase compared with the run-in phase increased by 6.4% in the buprenorphine TDS group (35.6% vs 292%, respectively), compared with a decrease of 5.9% in the placebo group (40.4% vs 463%); no statistical analysis of sleep duration data was performed. Buprenorphine TDS was well tolerated, with adverse events generally similar to those associated with other opioids. The incidence of systemic adverse events in the double-blind phase was similar in the 2 treatment groups (28.9% buprenorphine TDS, 27.6% placebo), with the most common adverse events being nausea, dizziness, and vomiting. After patch removal, skin reactions (mainly mild or moderate pruritus and erythema) were seen in 35.6% of the buprenorphine TDS group and 25.5% of the placebo group.

CONCLUSIONS

In the population studied, buprenorphine TDS provided adequate pain relief, as well as improvements in pain intensity and duration of pain-free sleep. It may be considered a therapeutic option for the treatment of moderate to severe chronic pain.

Chronic fentanyl or buprenorphine infusion in the mouse: similar analgesic profile but different effects on immune responses

It is known that morphine has a negative impact on the immune responses. The potent opioids fentanyl and buprenorphine have recently become available as transdermal preparation for the treatment of chronic pain. We analyze the effect of fentanyl and buprenorphine on splenic cellular immune responses in the mouse. The parameters evaluated were lymphoproliferation, natural killer cell activity and interleukin-2 and interferon-gamma production. Drugs were administered acutely at the equianalgesic doses of 0.25 mg/kg for fentanyl and 5 mg/kg for buprenorphine, or delivered continuously with osmotic pumps for 24 h, 3 and 7 days at the rate of 7.5 microg/h per mouse (fentanyl) and 12.5 microg/h per mouse (buprenorphine). After acute administration, a significant decrease of lymphoproliferation is observed in fentanyl-treated animals only. After 24 h of fentanyl administration all the parameters were significantly reduced. After 3 days of fentanyl infusion NK activity had returned to normal values, while all the other parameters were still significantly reduced. In 7 day fentanyl-treated animals immunological tolerance had developed, since no differences with controls were present. In contrast no immune alterations were ever present in buprenorphine-treated animals. No tolerance to the antinociceptive effect of drugs had yet developed. After 1 week of infusion with fentanyl and buprenorphine, new pumps were implanted releasing double amounts of drugs. Neither fentanyl nor buprenorphine-treated animals showed altered immune responses at any time considered. These results indicate that fentanyl and buprenorphine exert different immune effects. Opioid-induced immunosuppression is less relevant in chronic administration than in acute or short-time administration.