Transdermal buprenorphine

Hollow microneedles as a flexible dosing control solution for transdermal drug delivery

Microneedles, small needle-like structures typically less than 1000 μm in length, are effective tools for transporting substances across biological barriers via minimally invasive pathways. Various microelectromechanical system (MEMS) processes enable the production of different types of microneedles, including solid, coated, dissolving, hydrogel, and hollow microneedles, each tailored to specific drug and fluid delivery mechanisms. Among these, hollow microneedles stand out for their ability to offer flexible dosage control adaptable to varying drug formulations, making them particularly promising for transdermal drug delivery systems. This review examines the fabrication processes of hollow microneedles, highlights the advantages of their hollow structure for medical applications, and discusses the key factors influencing their performance. Finally, it proposes directions for advancing these technologies in both industrial and research settings.

Transdermal Opioids and the Quality of Life of the Cancer Patient: A Systematic Literature Review

OBJECTIVE

This systematic literature review aims to evaluate the effectiveness of transdermal opioids in managing cancer pain and their impact on the quality of life (QoL) of patients.

DATA SOURCES

A systematic literature review conducted following the PRISMA protocol, focusing on randomized clinical trials found in the Lilacs, Embase, PubMed, and SciELO databases over the last 20 years.

STUDY SELECTION AND DATA EXTRACTION

We included randomized clinical trials, published in English, Portuguese, or Spanish, which assessed the impact of transdermal opioids on the QoL. Data extraction was facilitated using the Rayyan app.

DATA SYNTHESIS

Six articles meeting the inclusion and exclusion criteria were analyzed. These studies covered a population ranging from 24 to 422 cancer patients experiencing moderate to severe pain. The risk of bias was assessed in each study, generally being categorized as uncertain or high.

RELEVANCE TO PATIENT CARE AND CLINICAL PRACTICE

The findings indicate that the analgesic effectiveness and side effects of transdermal formulations (specifically buprenorphine and fentanyl) for managing moderate to severe cancer pain are comparable to, or in some cases superior to, those of oral opioids traditionally employed.

CONCLUSIONS

Transdermal therapy was suggested to have several advantages over oral opioid therapy in enhancing cancer patients' QoL. These benefits span various dimensions, including pain management, physical functioning, mental health, vitality, overall patient improvement, anger/aversion, strength/activity, general QoL, cognitive and emotional functions, fatigue, and insomnia.

Long-term efficacy and reduced side-effects of buprenorphine in patients with moderate and severe chronic pain

Background

Chronic pain significantly impacts quality of life and poses substantial public health challenges. Buprenorphine, a synthetic analog of thebaine, is recognized for its potential in managing moderate to severe chronic pain with fewer side effects and a lower incidence of tolerance compared to traditional opioids.

Objective

This retrospective study aimed to assess the long-term efficacy and safety of buprenorphine transdermal patches in patients with moderate and severe chronic pain, with a focus on pain relief sustainability and tolerance development.

Methods

This retrospective observational study involved 246 patients prescribed buprenorphine transdermal patches. We evaluated changes in pain intensity using the Numeric Rating Scale (NRS), assessed opioid tolerance based on FDA guidelines for morphine-equivalent doses, and measured patient-reported outcomes through the Patients' Global Impression of Change (PGIC). Any adverse events were also recorded.

Results

Over the 36-month period, there was a significant reduction in NRS scores for both moderate and severe pain patients, demonstrating buprenorphine's sustained analgesic effect. Tolerance measurement indicated that no patients required increases in morphine-equivalent doses that would meet or exceed the FDA's threshold for opioid tolerance (60 mg/day of morphine or equivalent). Additionally, patient satisfaction was high, with the PGIC reflecting significant improvements in pain management and overall wellbeing. The side effects were minimal, with skin reactions and nausea being the most commonly reported but manageable adverse events.

Conclusion

The study findings validate the long-term use of buprenorphine transdermal patches as an effective and safe option for chronic pain management, maintaining efficacy without significant tolerance development. These results support the continued and expanded use of buprenorphine in clinical settings, emphasizing its role in reducing the burdens of chronic pain and opioid-related side effects. Further research is encouraged to refine pain management protocols and explore buprenorphine's full potential in diverse patient populations.

Evaluation of physical variables, thermal nociceptive threshold testing and pharmacokinetics during placement of transdermal buprenorphine matrix-type patch in healthy adult horses

Background

Matrix type transdermal buprenorphine patches have not been investigated in horses and may provide an effective means of providing continuous pain control for extended period and eliminating venous catheterization.

Objective

Assessment of the physiological variables (heart rate, respiratory rate, body temperature) and thermal nociceptive threshold testing, and describing the pharmacokinetic profile of transdermal buprenorphine matrix-type patch (20 μg h-1 and 40 μg h-1 dosing) in healthy adult horses.

Study design

Randomised experimental study with a Latin-square design.

Methods

Six adult healthy horses received each of the three treatments with a minimum 10 day washout period. BUP0 horses did not receive a patch (control). BUP20 horses received one patch (20 μg h-1) applied on the ventral aspect of the tail base resulting in a dose of 0.03-0.04 μg kg-1 h-1. BUP40 horses received two patches placed alongside each other (40 μg h-1) on the tail base resulting in a dose of 0.07-0.09 μg kg-1 h-1. Whole blood samples (for determination of buprenorphine concentration), physiological variables and thermal threshold testing were performed before (0 h) and at 2, 4, 8, 12, 16, 24, 32, 40, 48, 56, 64, 72, and 96 h after patch application. The patches were removed 72 h following placement and were analyzed for residual buprenorphine content.

Results

Between the three groups, there was no change in physiological variables across timepoints as compared to baseline (p > 0.1). With the higher dose, there was a significant increase in thermal thresholds from baseline values from 2 h until 48 h and these values were significantly higher than the group receiving the lower patch dose for multiple timepoints up to 40 h. 40 μg h-1 patch led to consistent measurable plasma concentrations starting at 2 h up to 96 h, with the mean plasma concentrations of > 0.1 ng/ml from 4 h to 40 h.

Conclusions

20 μg h-1 and 40 μg h-1 patch doses were well tolerated by all horses. At higher dose, plasma buprenorphine concentrations were more consistently measurable and blunted thermal thresholds for 48 h vs. 32 h with 20 μg h-1 dosing as compared to control.

Clinical efficacy of buprenorphine after oral dosing in rats undergoing major surgery

Serum corticosterone, serum buprenorphine, body weight change, consumption of food and water and behaviour-based pain assessment were measured in catheterised and non-catheterised male Wistar rats undergoing myocardial infarct (MI) surgery under general anaesthesia following buprenorphine dosing by subcutaneous (Bup-SC, 0.05 mg/kg) and oral (Bup-O, 0.4 mg/kg) routes. Buprenorphine was dosed subcutaneously at half an hour before and 8, 16 and 24 hours after surgery (Bup-SC), orally at one hour before surgery (Bup-O1) or at one hour before and 12 hours after surgery (Bup-O2) in catheterised rats and at one hour before and 24 hours after surgery (Bup-O24) in non-catheterised rats. Serum corticosterone, body weight changes and food and water consumption were not significantly different between treatments in catheterised rats. Bup-SC resulted in rapidly decreasing serum concentrations below the clinically effective concentrations (1 ng/mL) already at two hours after the first dose. Bup-O provided significantly higher and slowly decreasing serum concentrations, at or above clinically effective concentrations, for 24 hours (Bup-O1) and 42 hours (Bup-O2) after surgery. In non-catheterised rats, body weight development and food consumption were significantly higher in Bup-O24 rats compared to Bup-SC rats. The results indicate that a SC buprenorphine dose of 0.05 mg/kg every eight hours provides long periods of serum concentrations below clinically effective levels, and that a higher dose and/or more frequent dosage are required to provide stable serum concentrations at or above clinically effective levels. A single oral buprenorphine dose of 0.4 mg/kg provides clinically effective and stable serum concentrations for 24 hours in rats after MI surgery.

Comparison of the Transdermal and Intravenous Administration of Buprenorphine in the Management of Intra- and Postoperative Pain in Dogs Undergoing a Unilateral Mastectomy

The aim of this prospective clinical study was to evaluate the effectiveness of transdermal patches of buprenorphine as an alternative route for the management of perioperative pain in dogs undergoing a unilateral mastectomy. Our hypothesis was that the transdermal route would allow the obtainment of an analgesic plan comparable to that of the injectable administration. Twelve dogs were divided in two groups. In the BupreP group (six dogs), buprenorphine patches were applied 40 h before the start of the surgery, guaranteeing a dosage of 5−6 μg/kg/h. In the BupreI group (six dogs), 20 μg/kg of buprenorphine was administered intravenously 30 min before the induction of anesthesia, and this was repeated every 6 h for 24 h. The main physiological parameters, sedation scores (0 = no sedation; 11 = deep sedation), and pain scores were monitored from 30 min before the surgery to 24 h after the end of anesthesia. All p values < 0.05 were defined as statistically significant. Thirty minutes before the surgery, the sedation scores were higher in BupreI (score = 10) compared to the BupreP group (score = 1). Moreover, during the mastectomy, the mean arterial pressure significantly increased in both groups even if nobody required additional analgesia. In the postoperative period, the pain scores did not show statistically significant differences between the two groups, maintaining values below the pain threshold at all times of the study. In conclusion, the transdermal administration of buprenorphine could guarantee an analgesic quality equal to that of the injectable route.

Assessment of the Safety and Efficacy of Pre-emptive Use of Extended-release Buprenorphine for Mouse Laparotomy

Buprenorphine is commonly used to control postoperative pain in rodents. Short-acting formulations of buprenorphine (bup-HCl) require frequent handling and restraint of animals for appropriate dosing, which can be stressful and confound research outcomes. Ethiqa XR (bup-ER) is an FDA-indexed extended-release buprenorphine formulation that is an alternative to bup-HCl in mice and rats. In the current study, we first evaluated the pharmacokinetics of bup-ER in male C57BL/6J mice by sampling blood at 10 time points, ranging from 30 min to 72 h after administration (n = 3 mice per time point). Average plasma concentrations fell below therapeutic levels at 48 h after administration. We also evaluated the safety of bup-ER when administered prior to surgery in combination with common anesthetics and the efficacy of bup-ER in mouse laparotomy. Anesthetic safety was studied by measuring respiratory rate, rectal temperature, and recovery time in groups of mice (n = 8) given bup-HCl, bup-ER, or saline in combination with isoflurane or ketamine-xylazine anesthesia. No differences were seen between analgesic treatment groups with either of the general anesthetics. To evaluate efficacy, mice (n = 10) were randomly allocated to receive either bup-ER (3.25 mg/kg) once presurgically, bup-HCl (0.1 mg/kg) presurgically and then every 8 h, or saline once before surgery. Mice underwent a sham laparotomy and were assessed for pain based on changes in weight, cageside ethogram, nesting consolidation test, rearing frequency, and nociception to von Frey testing at 6, 12, 24, 48, and 72 h after surgery. Cageside ethogram, rearing frequency, and von Frey testing showed significant differences between bup-ER-treated mice and saline controls in the early postoperative period. No significant effects between treatment groups were seen in daily weights or nesting consolidation scores. This study demonstrates that bup-ER can be safely administered before surgery and provides analgesia for up to 48 h after administration based on pharmacokinetic and behavioral data.

Transdermal buprenorphine for pain management in children

Pain is one of the main symptoms reported by sick children, particularly by those suffering from cancer. Opioids are very useful in controlling this symptom but they are burdened with significant side effects that limit their use in children. Buprenorphine is a strong opioid that, due to its particular pharmacological characteristics, ensures excellent pain relief with fewer side effects than other opioids. The transdermal formulation allows for good pain control associated with optimal compliance by patients and few limitations on daily life. Unfortunately, transdermal buprenorphine use remains off-label for the control of chronic pain in children; therefore, it is desirable that new studies can validate its use in the paediatric population. This review aims to analyse the clinical advantages of transdermal buprenorphine in the paediatric population and the possible side effects registered in daily clinical practice.

Pharmacokinetics of Single-Dose Intramuscular and Subcutaneous Injections of Buprenorphine in Common Marmosets (Callithrix jacchus)

Although buprenorphine is the most frequently used opioid analgesic in common marmosets (Callithrix jacchus), there is limited information in the literature supporting current dosing regimens used for this species. The purpose of this study was to determine the pharmacokinetic profiles of single-dose buprenorphine HCl administered intramuscularly (IM) at 0.01 mg/kg in 6 adult marmosets (1.8 to 12.8 y old; 2 males, 4 females) and subcutaneously (SQ) at 0.01 mg/kg in 6 adult marmo- sets (2.3-4.4 y old; 3 males, 3 females) by mass spectrometry. Blood was collected at multiple time points from 0.25 to 24 h from unsedated animals following a hybrid sparse-serial sampling design. The maximal observed plasma concentration of buprenorphine (Cmax ) administered IM (2.57 ± 0.95 ng/mL) was significantly higher than administered SQ (1.47 ± 0.61 ng/mL). However, the time to Cmax (Tmax) was not statistically different between routes (17.4 ± 6 min for IM and 19.8 ± 7.8 min for SQ). The time of the last quantifiable concentration of buprenorphine was 5 ± 1.67 h for IM compared with 6.33 ± 1.51 h for SQ, which was not statistically different. The mean buprenorphine plasma concentration-time curves were used to propose a dosing frequency of 4 to 6 h for buprenorphine at 0.01 mg/kg IM or SQ based on a theoretical therapeutic plasma concentration threshold of 0.1 ng/mL. Based on the mean pharmacokinetic parameters and plasma-concentration time curves, both IM and SQ routes of buprenorphine at this dose provide a rapid increase in the plasma concentration of buprenorphine above the therapeutic threshold, and may be more effective for acute rather than long-lasting analgesia. Further studies are needed to examine repeated dosing regimens and the efficacy of buprenorphine in common marmosets.

Explaining differential effects of medication for opioid use disorder using a novel approach incorporating mediating variables

BACKGROUND AND AIMS

A recent study found that homeless individuals with opioid use disorder (OUD) had a lower risk of relapse on extended-release naltrexone (XR-NTX) versus buprenorphine-naloxone (BUP-NX), whereas non-homeless individuals had a lower risk of relapse on BUP-NX. This secondary study examined differences in mediation pathways to medication effect between homeless and non-homeless participants.

DESIGN

Secondary analysis of an open-label randomized controlled, 24-week comparative effectiveness trial, 2014-17.

SETTING

Eight community addiction treatment programs in the United States.

PARTICIPANTS

English-speaking adults with DSM-5 OUD, recruited during inpatient admission (n = 570).

INTERVENTION(S)

Randomization to monthly injection of XR-NTX or daily sublingual BUP-NX.

MEASUREMENTS(S)

Mediation analysis estimated the direct effect of XR-NTX versus BUP-NX on relapse and indirect effect through mediators of medication adherence, use of illicit opioids, depressive symptoms and pain, separately by homeless status.

FINDINGS

For the homeless subgroup, the protective indirect path contributed a 3.4 percentage point reduced risk of relapse [95% confidence interval (CI) = -12.0, 5.3] comparing XR-NTX to BUP-NX (explaining 21% of the total effect). For the non-homeless subgroup, the indirect path contributed a 9.4 percentage point increased risk of relapse (95% CI = 3.1, 15.7) comparing XR-NTX to BUP-NX (explaining 57% of the total effect).

CONCLUSIONS

A novel approach to mediation analysis shows that much of the difference in medication effectiveness (extended-release naltrexone versus buprenorphine-naloxone) on opioid relapse among non-homeless adults with opioid use disorder appears to be explained by mediators of adherence, illicit opioid use, depressive symptoms and pain.

Comparative evaluation of analgesic efficacy of buprenorphine transdermal patch and fentanyl patch in management of postoperative pain after arthroscopic lower limb surgery: A randomized controlled trial

Background and Aims

Transdermal opioids are newer modality in use for the control of postoperative pain, because of its noninvasiveness, longer duration of action, sustained blood levels, and with minimal side effects. The study was aimed to evaluate the efficacy of analgesia of buprenorphine patch 10, 20 μg·h^-1 and fentanyl patch 25 μg·h^-1 for relief of pain in the postoperative period in patients undergoing arthroscopic lower limb surgeries.

Materials and Methods

It was a randomized, double-blinded, prospective study in which adult patients undergoing lower limb arthroscopic surgery were randomly segregated into three groups. In Group 1 (fentanyl patch 25 μg·h^-1), Group 2 (buprenorphine patch 10 μg·h^-1), and Group 3 (buprenorphine patch 20 μg·h^-1), transdermal patches were applied 12 h prior to surgery. Mean NRS score, total rescue analgesic requirement, drug-related adverse effects, and hemodynamic status were evaluated till 72 h in the postoperative period.

Results

Out of 175 screened patients, 150 patients were finally analyzed. Baseline characteristics were the same among all the three groups. Median NRS score was lowest in Group 3 [P value < 0.05 at 2, 4, 8, 12, and 24 h after surgery (Kruskal Wallis test). The total consumption of postoperative rescue analgesic diclofenac was the lowest in Group 3 as compared to other groups without any significant increase in adverse events.

Conclusions

In arthroscopic lower limb surgery, buprenorphine patch (20 μg·h^-1) applied 12 h prior to surgery is an effective postoperative analgesic and it is not associated with any significant adverse effects.

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

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

Predicting Opioid Therapy Safety In Pancreatic Cancer Patients

Background — Obligatory use of strong opioids for treating chronic pain syndrome in patients with pancreatic cancer provides the implementation of opioid-associated adverse reactions. Genetic and non-genetic risk factors are predictive of the opioid therapy safety. Contemporary methods of information analysis allow using prognostic risk models for practical application. Objective — Identification of significant risk factors for the development of opioid-associated adverse drug reactions in patients with chronic pain syndrome against the background of pancreatic cancer. Material and Methods — The study included 90 patients with chronic pain against the background of pancreatic cancer, randomized at a ratio of 1: 1. Group 1 received morphine sulfate (MS), group 2 received fentanyl transdermal therapeutic system (FTTS) with standard adjuvant therapy (ketoprofen, diazepam, amitriptyline). To assess pain level, the 10-point Digital Rating Scale, the Visual Analogue Scale and the pain questionnaires were used. The assessment of the treatment safety was conducted by the Naranjo Scale. Assessment of prognostic genetic and non-genetic factors was carried out using ROC analysis with calculation of AUC (the area under the ROC-curve). Results — Prognostic models of good quality were determined with the optimal ratio of sensitivity and specificity for the influence of genetic and non-genetic risk factors on the development of opioid-associated adverse drug reactions (OA-ADRs) in comparison groups. Various prognostic factors, complementing each other, were identified in the comparison groups. Conclusion — The following OA-ADRs predicting factors were identified: for FTTS-associated nausea and vomiting – age and carriage of rs7438135 AG genotype of UGT2B7 gene; for local reactions – the sum of points on the ESAS scale and carriage of rs7438135 AA genotype of UGT2B7 gene; for difficulty urinating – the level of glomerular filtration rate; for neurotoxicity – the level of AST and bilirubin, and the carriage of rs1128503 GG genotype of ABCB1 gene; for pruritus – carriage of rs1045642642 AA genotype of ABCB1 gene. The prognostic factors for the implementation of MS-associated neurotoxicity were age and comorbidity; for dry mouth was predicted best from the sum of points on the MMCE scale; weakness was predicted by the carriage of rs7668258 TT genotype of UGT2B7 gene.

A comprehensive review of partial opioid agonists for the treatment of chronic pain

Chronic pain is a common condition that is being increasingly recognized, diagnosed, and treated in a variety of settings. Opioids can be used to treat chronic pain but at the cost of adverse effects and risk of dependence. Recently, there has been a movement to improve analgesic care in the setting of the opioid epidemic and the overprescribing of opioids, causing over-accessibility, dependence, and large numbers of overdose deaths. Opioid-specific receptors, including the μ, δ, κ, and opioid receptor like-1 (ORL-1) receptors, are each 7-transmembrane spanning proteins, which affect the G-protein and β-arrestin cascades. Each opioid class can act differently on the receptors, resulting in full, partial, or antagonizing effects. This comprehensive review looks at different agents in major classes, nonselective and mixed/partial agonists/antagonists, including the nonselective partial agonists, levorphanol and tramadol. Mixed partial agonists/antagonists include buprenorphine, pentazocine, nalbuphine, and butorphanol. Oliceridine is the only current selective partial agonist that agonizes specific pathways to promote analgesic effects and discourage adverse effects.

Buprenorphine for Cancer Pain in Patients With Nonmedical Opioid Use: A Retrospective Study at a Comprehensive Cancer Center

Background:

Outpatients with cancer commonly have nonmedical opioid use (NMOU) behaviors and use opioids to dull emotional and existential suffering. Buprenorphine is often used for cancer pain due to less reported euphoria when compared to other opioids.

Methods:

A retrospective review was done in patients who were prescribed buprenorphine for cancer pain. Pain scores were reported on a Likert pain scale of 1 to 10. Nonmedical opioid use was defined as patients taking opioids for emotional pain at or above the maximum prescribed amount.

Results:

For 16 patients, the mean pain score prior to buprenorphine (pain pre) was 8.3 (Standard deviation (Std) 1.6), and the mean pain score on follow-up post-buprenorphine (pain post) was 6.1 (Std 2.3) with a reduction in mean pain score (pain change) of −2.0 (Std 2.9, P = .059). Those patients without NMOU had a pain prescore of 9.5 (Std 1.0) and pain post of 4.3 (Std 2.5) with a mean pain change of −5.0 (Std 1.7, P = .20). The mean pain change in those with chemical coping (−1.3/Std 2.7), illicit drug use (−2.8/Std 1.0), or psychiatric comorbidity (−2.4/Std 2.7) were reduced after buprenorphine, however, not statistically significant. Outpatient rotation to buprenorphine was well tolerated.

Conclusions:

The pain score in those patients without NMOU was significantly lower after rotation to buprenorphine than those with NMOU. We deduce that in those with NMOU, it is more challenging to achieve pain relief with buprenorphine. Overall, for all patients, rotation to buprenorphine resulted in a marginally significantly reduced pain score.

Immunomodulation Associated with Sustained-release Buprenorphine in Female CD1 Mice Challenged with Ovalbumin

Opioid analgesics have immunomodulatory properties, which often result in immunosuppression. Sustained-release buprenorphine (SR-Bup) has recently become available as an analgesic for pain management in mice, and little is known regarding potential effects of SR-Bup on the murine immune response. To this end, we immunized female CD1 mice with ovalbumin in complete Freud adjuvant and then treated them with either saline, SR-Bup, Bup-HCl, or SR-vehicle (SR-Veh) for 18 d. Splenocytes were isolated for culture and stimulation to assess cytokine responses, and blood was collected to determine serum antibody responses to ovalbumin. In all treatment groups, levels of IL10, TNFα, and IFNγ increased in ovalbumin-stimulated splenocytes compared with unstimulated splenocytes. Cytokine responses after stimulation did not differ between treatment groups except for IL10, which was significantly higher in SR-Bup-treated mice compared with those given saline or Bup-HCl. The antibody response was significantly increased after immunization but did not differ across treatment groups, except that the response to SR-Veh was lower. These results suggest that the immunomodulatory effects of prolonged treatment with SR-Bup on innate and adaptive immunity are negligible.

Pharmacokinetics of a Long-lasting, Highly Concentrated Buprenorphine Solution after Subcutaneous Administration in Rhesus Macaques (Macaca mulatta)

Opioids are essential for use in rhesus macaques (Macaca mulatta) that require multimodal analgesia or those unable to receive NSAID as part of their pain management plan. The current opioid epidemic has universally limited the availability of these vital analgesics, compelling clinicians to investigate other options including novel opioid formulations. A commercially available injectable, long-lasting, highly concentrated buprenorphine solution (HCBS) provides therapeutic plasma concentrations lasting 24 h after a single dose in cats ( Felis catus). We hypothesized that this same HCBS would achieve therapeutic concentrations (≥0.1 ng/mL) for at least 24 h in rhesus macaques. In the current study, 6 healthy, adult rhesus macaques were included in a randomized, 2-period, 2-treatment crossover study. The low dose (0.24 mg/kg SC) achieved a peak plasma concentration of 19.1 ± 5.68 ng/mL at 0.308 ± 0.077 h, with an AUC of 236.4 ± 22.5 h/ng/mL and terminal elimination half-life of 19.6 ± 4.02 h; for the high dose (0.72 mg/kg SC), these parameters were 65.2 ± 14.7 ng/mL, 0.034 ± 0.004 h, 641.3 ± 79.4 h/ng/mL, and 20.6 ± 2.30 h, respectively. The mean plasma concentrations for the low and high doses in rhesus macaques significantly exceeded the therapeutic threshold for 48 and 72 h, respectively. One macaque showed mild somnolence at both doses, and another showed mild pruritus at both doses. These findings show that subcutaneous administration of HCBS provides prolonged and long-lasting therapeutic plasma levels for 48 to 72 h dosing without problematic adverse effects and thus represents a potential new analgesic alternative.

Evaluation of Analgesic Patches in Cynomolgus Macaques (Macaca fascicularis)

Opioids are widely used in veterinary and human medicine to manage pain. However, there is a paucity of information in the literature regarding the pharmacokinetics of opioid transdermal patches (TDP) in NHP. Therefore, to determine whether opioid TDP attain therapeutic concentrations in NHP, the pharmacokinetics of fentanyl (25 μg/h) and buprenorphine (10 and 20 μg/h) TDP were evaluated in naïve, adult, male cynomolgus macaques (n = 4) in a crossover study. Plasma opioid levels were determined by tandem liquid chromatography-mass spectrometry. The AUC_0-inf for fentanyl and the low and high dose buprenorphine patches were 115 ± 14, 462 ± 74, and 778 ± 344 ng× h/mL, and the plasma half-lifes were 22 ± 4, 77 ± 27, and 42 ± 11 h, respectively. No adverse effects were noted throughout the study. Minimal therapeutic concentrations for fentanyl (0.2 ng/mL) and buprenorphine (0.1 ng/mL) were achieved in all macaques within 8 h of fentanyl and 24 h of buprenorphine TDP application. Therapeutic levels for the fentanyl and low- and high-dose buprenorphine patches were maintained for 96, 120, and 144 h, respectively. These findings suggest that 25-μg/h fentanyl patches should be replaced every 4 d, and the low- and high-dose buprenorphine patches should be replaced every 5 and 6 d, respectively. The results of this study show that fentanyl and buprenorphine patches achieve minimal therapeutic levels for clinically relevant periods of time and should be considered viable options for pain management in cynomolgus macaques.

Treating Chronic Pain: An Overview of Clinical Studies Centered on the Buprenorphine Option

The buprenorphine receptor binding profile is unique in that it binds to all three major opioid receptors (mu, kappa, delta), and also binds to the orphan-like receptor, the receptor for orphanin FQ/nociceptin, with lower affinity. Within the mu receptor group, buprenorphine analgesia in rodents is dependent on the recently discovered arylepoxamide receptor target in brain, which involves a truncated 6-transmembrane mu receptor gene protein, distinguishing itself from morphine and most other mu opioids. Although originally designed as an analgesic, buprenorphine has mainly been used for opioid maintenance therapy and only now is increasingly recognized as an effective analgesic with an improved therapeutic index relative to certain potent opioids. Albeit a second-, third-, or fourth-line analgesic, buprenorphine is a reasonable choice in certain clinical situations. Transdermal patches and buccal film formulations are now commercially available as analgesics. This review discusses buprenorphine pharmacodynamics and pharmacokinetics, use in certain populations, and provides a synopsis of systematic reviews and randomized analgesic trials. We briefly discuss postoperative management in patients receiving buprenorphine maintenance therapy, opioid equivalence to buprenorphine, rotations to buprenorphine from other opioids, and clinical relevance of buprenorphine-related QTc interval changes.

Transdermal buprenorphine for moderate chronic noncancer pain syndromes

Introduction: Chronic noncancer pain has remained a challenging clinical problem. Opioid analgesics are effective, but they are known to be associated with opioid use disorder and potentially treatment-limiting side effects. Buprenorphine is a Schedule III synthetic opioid in the USA with a chemical structure similar to that of morphine but with a longer duration of action, greater potency, and other unique pharmacological attributes. Its role in treatment of chronic noncancer pain may be broader than currently thought.Areas covered: The pharmacokinetics, pharmacodynamics, clinical efficacy, and safety profile of transdermal buprenorphine in moderate chronic noncancer pain syndromes patients will be discussed.Expert commentary: Buprenorphine offers effective analgesia in the form of a Schedule III drug (rather than Schedule II such as oxycodone or morphine) and transdermal buprenorphine is a convenient, accepted, around-the-clock pain reliever. Its lower potential for abuse should make it a more desirable pain reliever but many payers do not reimburse buprenorphine, driving prescribers and their patients to generic versions of the riskier Schedule II oral opioids such as oxycodone and morphine.

Buprenorphine and pain treatment in pediatric patients: an update

Introduction

The usual management of moderate to severe pain is based on the use of opioids. Buprenorphine (BPN) is an opioid with an analgesic potency 50 times greater than that of morphine. It is widely used in various pain models and has demonstrated efficacy and safety in adult patients; however, there are insufficient clinical trials in pediatric populations.

Purpose

The aim of this study was to perform an updated meta-analysis on the implementation of BPN in the treatment of pain in the pediatric population.

Methods

A bibliographic search was carried out in different biomedical databases to identify scientific papers and clinical trials with evidence of BPN use in children and adolescents.

Results

A total of 89 articles were found, of which 66 were selected. Analysis of these items revealed additional sources, and the final review included a total of 112 publications.

Conclusion

Few studies were found regarding the efficacy and safety of BPN use in children. In recent years, the use of this drug in the pediatric population has become widespread, so it is imperative to perform clinical trials and pharmacological and pharmacovigilance studies, which will allow researchers to develop dosage schemes based on the evidence and minimize the risk of adverse effects.

The pharmacokinetics and analgesic effects of extended-release buprenorphine administered subcutaneously in healthy dogs

Buprenorphine is a partial μ agonist opioid used for analgesia in dogs. An extended-release formulation (ER-buprenorphine) has been shown to provide effective analgesia for 72 hr in rats and mice. Six healthy mongrel dogs were enrolled in a randomized, blinded crossover design to describe and compare the pharmacokinetics and pharmacodynamics of ER-buprenorphine administered subcutaneous at 0.2 mg/kg (ER-B) and commercially available buprenorphine for injection intravenously at 0.02 mg/kg (IV-B). After drug administration, serial blood samples were collected to measure plasma buprenorphine concentrations using liquid chromatography/mass spectrometry detection. Heart rate, respiratory rate, body temperature, sedation score, and thermal threshold latency were recorded throughout the study. Median (range) terminal half-life, time to maximum concentration, and maximum plasma concentration of ER-buprenorphine were 12.74 hr (10.43-18.84 hr), 8 hr (4-36 hr), and 5.00 ng/ml (4.29-10.98 ng/ml), respectively. Mild bradycardia, hypothermia, and inappetence were noted in both groups. Thermal threshold latency was significantly prolonged compared to baseline up to 12 hr and up to 72 hr in IV-B and ER-B, respectively. These results showed that ER-buprenorphine administered at a dose of 0.2 mg/kg resulted in prolonged and sustained plasma concentrations and antinociceptive effects up to 72 hr after drug administration.

Getting Drugs Across Biological Barriers

The delivery of drugs to a target site frequently involves crossing biological barriers. The degree and nature of the impediment to flux, as well as the potential approaches to overcoming it, depend on the tissue, the drug, and numerous other factors. Here an overview of approaches that have been taken to crossing biological barriers is presented, with special attention to transdermal drug delivery. Technology and knowledge pertaining to addressing these issues in a variety of organs could have a significant clinical impact.

Influence of UGT2B7, CYP3A4, and OPRM1 Gene Polymorphisms on Transdermal Buprenorphine Pain Control in Patients with Critical Lower Limb Ischemia Awaiting Revascularization

BACKGROUND

Pain control in critical limb ischemia (CLI) varies considerably between individuals.

OBJECTIVE

To evaluate pharmacogenetically the response to transdermal buprenorphine (BUP-TTS) in patients with CLI who are awaiting revascularization.

METHODS

One hundred and seven patients with CLI were treated with BUP-TTS. The following were analyzed: (1) pain perception (visual analog scale (VAS) before and 4 days after treatment) and (2) genetics: glucuronosyltransferase (UGT2B7), cytochrome (CYP3A4), and μ-opioid receptor (OPRM1) gene polymorphisms.

RESULTS

Ninety-three patients completed the study. The VAS score by the fourth day of analgesia dropped from 6.82 to 3.38 (P < 0.05). The analgesic response to BUP-TTS was greater in men than in women (P = 0.019). Patients who were AA homozygotes for the CYP3A4 gene showed the best response to analgesic treatment (P = 0.003). The combination of the CYP3A4 gene with UGT2B7 or OPRM1 was favorable to the effect of the CYP3A4 gene (P = 0.045 and P = 0.026, respectively). The combination of UGT2B7 with OPRM1 was ineffective (P = 0.648). The 3 polymorphisms together had no effect on response to treatment (P = 0.461).

CONCLUSIONS

BUP-TTS is efficacious in the control of pain in patients with CLI. The homozygous AA carriers of the CYP3A4 gene respond better to treatment with BUP-TTS.

On the selection of an opioid for local skin analgesia: Structure-skin permeability relationships

Recent studies demonstrated that post-herpetical and inflammatory pain can be locally managed by morphine gels, empirically chosen. Aiming to rationalize the selection of the most suitable opioid for the cutaneous delivery, we studied the in vitro penetration through human epidermis of eight opioids, evidencing the critical modifications of the morphinan core. Log P, log D, solid-state features and solubility were determined. Docking simulations were performed using supramolecular assembly made of ceramide VI. The modifications on position 3 of the morphinan core resulted the most relevant in determining both physicochemical characteristics and diffusion pattern. The 3-methoxy group weakened the cohesiveness of the crystal lattice structure and increased the permeation flux (J). Computational studies emphasized that, while permeation is essentially controlled by molecule apolarity, skin retention depends on a fine balance of polar and apolar molecular features. Moreover, ChemPLP scoring the interactions between the opioids and ceramide, correlated with both the amount retained into the epidermis (Qret) and J. The balance of the skin penetration properties and the affinity potency for μ-receptors evidenced hydromorphone as the most suitable compound for the induction of local analgesia.

Buprenorphine for treating cancer pain

BACKGROUND

Many patients with cancer experience moderate to severe pain that requires treatment with strong analgesics. Buprenorphine, fentanyl and morphine are examples of strong opioids used for cancer pain relief. However, strong opioids are ineffective as pain treatment in all patients and are not well-tolerated by all patients. The aim of this Cochrane review is to assess whether buprenorphine is associated with superior, inferior or equal pain relief and tolerability compared to other analgesic options for patients with cancer pain.

OBJECTIVES

To assess the effectiveness and tolerability of buprenorphine for pain in adults and children with cancer.

SEARCH METHODS

We searched CENTRAL (the Cochrane Library) issue 12 or 12 2014, MEDLINE (via OVID) 1948 to 20 January 2015, EMBASE (via OVID) 1980 to 20 January 2015, ISI Web of Science (SCI-EXPANDED & CPCI-S) to 20 January 2015, ISI BIOSIS 1969 to 20 January 2015. We also searched ClinicalTrials.gov (http://clinicaltrials.gov/; metaRegister of Controlled Trials (mRCT) (http://www.controlled-trials.com/mrct/), the World Health Organization (WHO) International Clinical Trials Registry Platform (ICTRP) search portal (http://apps.who.int/trialsearch/) and the Proceedings of the Congress of the European Federation of International Association for the Study of Pain (IASP; via European Journal of Pain Supplements) on 16 February 2015. We checked the bibliographic references of identified studies as well as relevant studies and systematic reviews to find additional trials not identified by the electronic searches. We contacted authors of included studies for other relevant studies.

SELECTION CRITERIA

We included randomised controlled trials, with parallel-group or crossover design, comparing buprenorphine (any formulation and any route of administration) with placebo or an active drug (including buprenorphine) for cancer background pain in adults and children.

DATA COLLECTION AND ANALYSIS

Two review authors independently extracted data pertaining to study design, participant details (including age, cancer characteristics, previous analgesic medication and setting), interventions (including details about titration) and outcomes, and independently assessed the quality of the included studies according to standard Cochrane methodology. As it was not feasible to meta-analyse the data, we summarised the results narratively. We assessed the overall quality of the evidence for each outcome using the GRADE approach.

MAIN RESULTS

In this Cochrane review we identified 19 relevant studies including a total of 1421 patients that examined 16 different intervention comparisons.Of the studies that compared buprenorphine to another drug, 11 studies performed comparative analyses between the randomised groups, and five studies found that buprenorphine was superior to the comparison treatment. Three studies found no differences between buprenorphine and the comparison drug, while another three studies found treatment with buprenorphine to be inferior to the alternative treatment in terms of the side effects profile or patients preference/acceptability.Of the studies that compared different doses or formulations/routes of administration of buprenorphine, pain intensity ratings did not differ significantly between intramuscular buprenorphine and buprenorphine suppository. However, the average severity of dizziness, nausea, vomiting and adverse events as a total were all significantly higher in the intramuscular group relatively to the suppository group (one study).Sublingual buprenorphine was associated with faster onset of pain relief compared to subdermal buprenorphine, with similar duration analgesia and no significant differences in adverse event rates reported between the treatments (one study).In terms of transdermal buprenorphine, two studies found it superior to placebo, whereas a third study found no difference between placebo and different doses of transdermal buprenorphine.The studies that examined different doses of transdermal buprenorphine did not report a clear dose-response relationship.The quality of this evidence base was limited by under-reporting of most bias assessment items (e.g., the patient selection items), by small sample sizes in several included studies, by attrition (with data missing from 8.2% of the enrolled/randomised patients for efficacy and from 14.6% for safety) and by limited or no reporting of the expected outcomes in a number of cases. The evidence for all the outcomes was very low quality.

AUTHORS' CONCLUSIONS

Based on the available evidence, it is difficult to say where buprenorphine fits in the treatment of cancer pain with strong opioids. However, it might be considered to rank as a fourth-line option compared to the more standard therapies of morphine, oxycodone and fentanyl, and even there it would only be suitable for some patients. However, palliative care patients are often heterogeneous and complex, so having a number of analgesics available that can be given differently increases patient and prescriber choice. In particular, the sublingual and injectable routes seemed to have a more definable analgesic effect, whereas the transdermal route studies left more questions.

Buprenorphine for treating cancer pain

BACKGROUND

Many patients with cancer experience moderate to severe pain that requires treatment with strong analgesics. Buprenorphine, fentanyl and morphine are examples of strong opioids used for cancer pain relief. However, strong opioids are ineffective as pain treatment in all patients and are not well-tolerated by all patients. The aim of this Cochrane review is to assess whether buprenorphine is associated with superior, inferior or equal pain relief and tolerability compared to other analgesic options for patients with cancer pain.

OBJECTIVES

To assess the effectiveness and tolerability of buprenorphine for pain in adults and children with cancer.

SEARCH METHODS

We searched CENTRAL (the Cochrane Library) issue 12 or 12 2014, MEDLINE (via OVID) 1948 to 20 January 2015, EMBASE (via OVID) 1980 to 20 January 2015, ISI Web of Science (SCI-EXPANDED & CPCI-S) to 20 January 2015, ISI BIOSIS 1969 to 20 January 2015. We also searched ClinicalTrials.gov (http://clinicaltrials.gov/; metaRegister of Controlled Trials (mRCT) (http://www.controlled-trials.com/mrct/), the World Health Organization (WHO) International Clinical Trials Registry Platform (ICTRP) search portal (http://apps.who.int/trialsearch/) and the Proceedings of the Congress of the European Federation of International Association for the Study of Pain (IASP; via European Journal of Pain Supplements) on 16 February 2015. We checked the bibliographic references of identified studies as well as relevant studies and systematic reviews to find additional trials not identified by the electronic searches. We contacted authors of included studies for other relevant studies.

SELECTION CRITERIA

We included randomised controlled trials, with parallel-group or crossover design, comparing buprenorphine (any formulation and any route of administration) with placebo or an active drug (including buprenorphine) for cancer background pain in adults and children.

DATA COLLECTION AND ANALYSIS

Two review authors independently extracted data pertaining to study design, participant details (including age, cancer characteristics, previous analgesic medication and setting), interventions (including details about titration) and outcomes, and independently assessed the quality of the included studies according to standard Cochrane methodology. As it was not feasible to meta-analyse the data, we summarised the results narratively. We assessed the overall quality of the evidence for each outcome using the GRADE approach.

MAIN RESULTS

In this Cochrane review we identified 19 relevant studies including a total of 1421 patients that examined 16 different intervention comparisons.Of the studies that compared buprenorphine to another drug, 11 studies performed comparative analyses between the randomised groups, and five studies found that buprenorphine was superior to the comparison treatment. Three studies found no differences between buprenorphine and the comparison drug, while another three studies found treatment with buprenorphine to be inferior to the alternative treatment in terms of the side effects profile or patients preference/acceptability.Of the studies that compared different doses or formulations/routes of administration of buprenorphine, pain intensity ratings did not differ significantly between intramuscular buprenorphine and buprenorphine suppository. However, the average severity of dizziness, nausea, vomiting and adverse events as a total were all significantly higher in the intramuscular group relatively to the suppository group (one study).Sublingual buprenorphine was associated with faster onset of pain relief compared to subdermal buprenorphine, with similar duration analgesia and no significant differences in adverse event rates reported between the treatments (one study).In terms of transdermal buprenorphine, two studies found it superior to placebo, whereas a third study found no difference between placebo and different doses of transdermal buprenorphine.The studies that examined different doses of transdermal buprenorphine did not report a clear dose-response relationship.The quality of this evidence base was limited by under-reporting of most bias assessment items (e.g., the patient selection items), by small sample sizes in several included studies, by attrition (with data missing from 8.2% of the enrolled/randomised patients for efficacy and from 14.6% for safety) and by limited or no reporting of the expected outcomes in a number of cases. The evidence for all the outcomes was very low quality.

AUTHORS' CONCLUSIONS

Based on the available evidence, it is difficult to say where buprenorphine fits in the treatment of cancer pain with strong opioids. However, it might be considered to rank as a fourth-line option compared to the more standard therapies of morphine, oxycodone and fentanyl, and even there it would only be suitable for some patients. However, palliative care patients are often heterogeneous and complex, so having a number of analgesics available that can be given differently increases patient and prescriber choice. In particular, the sublingual and injectable routes seemed to have a more definable analgesic effect, whereas the transdermal route studies left more questions.

Modeling nociception in zebrafish: a way forward for unbiased analgesic discovery

Acute and chronic pain conditions are often debilitating, inflicting severe physiological, emotional and economic costs and affect a large percentage of the global population. However, the development of therapeutic analgesic agents based primarily on targeted drug development has been largely ineffective. An alternative approach to analgesic development would be to develop low cost, high throughput, untargeted animal based behavioral screens that model complex nociceptive behaviors in which to screen for analgesic compounds. Here we describe the development of a behavioral based assay in zebrafish larvae that is effective in identifying small molecule compounds with analgesic properties. In a place aversion assay, which likely utilizes supraspinal neuronal circuitry, individually arrayed zebrafish larvae show temperature-dependent aversion to increasing and decreasing temperatures deviating from rearing temperature. Modeling thermal hyperalgesia, the addition of the noxious inflammatory compound and TRPA1 agonist allyl isothiocyanate sensitized heat aversion and reversed cool aversion leading larvae to avoid rearing temperature in favor of otherwise acutely aversive cooler temperatures. We show that small molecules with known analgesic properties are able to inhibit acute and/or sensitized temperature aversion.

Buprenorphine for pain relief in mice: repeated injections vs sustained-release depot formulation

Sustained-release formulations of analgesic drugs are promising alternatives to repeated drug injections. Here, we compared a sustained-release formulation of buprenorphine (SB, 2.2 mg/kg) with a standard protocol of three injections of buprenorphine (Temgesic, 0.1 mg/kg/8 h) in mice. Buprenorphine serum concentration and analgesic action (thermal sensitivity) were determined in healthy mice. Additionally, the pain relief properties of both protocols were assessed after laparotomy using physiological and ethological measures of pain and recovery. Serum concentrations and thermal sensitivity tests indicated duration of action of at least 4 h (but less than 8 h) with the Temgesic protocol, and 24–48 h with SB. Behavioural and clinical parameters indicated at least partial pain relief after surgery for both protocols. Observed side-effects of buprenorphine independent of the protocol were increased activity, disturbed circadian rhythm and several abnormal behaviours. A tendency for decreased food and water intake as well as body weight reduction was also seen. Body weight decreased significantly in animals that received three injections of Temgesic, regardless of whether surgery was performed or not ( P = 0.015; P = 0.023), hinting at a stress response towards this repeated intervention. In conclusion, an application interval of 8 h (Temgesic) appears too long and might lead to repeated periods with insufficient analgesia in animals undergoing lasting and/or substantial pain after surgery. In comparison to the standard protocol, SB provided a long-lasting, assured analgesia without possible stressful repeated injections in a standard surgical model, with only limited and acceptable behavioural side-effects.

Buprenorphine for Cancer Pain

Buprenorphine (BUP) is a semisynthetic derivative of the opium alkaloid thebaine found in the poppy Papaver somniferum. Its chemical structure contains the morphine structure but differs by having a cyclopropylmethyl group. Buprenorphine is a potent µ opioid agonist. Buprenorphine undergoes extensive first-pass metabolism in the liver and gut. The development of a transdermal BUP formulation in 2001 led to its evaluation in cancer pain. This article provides the practitioner with an update on the current role of BUP in cancer care. It highlights data suggesting effectiveness in various types of cancer pain. The article reviews pharmacology, routes of administration, adverse effects, drug interactions, and cost considerations.

Retrospective analysis of 4 years of clinical experience with transdermal buprenorphine (Transtec®) in post-traumatic pain

SUMMARY: 

Aims: To evaluate the effectiveness and safety of transdermal buprenorphine (BTDS) in the treatment of post-traumatic pain in a working population. Patients & methods: Retrospective case series of patients with severe post-traumatic pain treated with BTDS between 2008 and 2012. Results: 57 patients were evaluated: 38 men, 19 women (mean age 43 years); patients with burns (n = 22), skin degloving (14), open dislocations (eight), traumatic nerve lesions (six), spinal cord injury (four) and limb amputations (three). 25, 12 and 20 patients experienced neuropathic pain, nociceptive pain or neuropathic/nociceptive pain, respectively. The mean baseline DN4 questionnaire and pain intensity scores were 4.8±2.3 and 7.4±1.5, respectively. The mean duration of pain before BTDS use was 24.4 months (>3 months in 65% of patients). Total patient-years of BTDS treatment were 73. After 14.7±14.9 months of BTDS treatment, mean pain intensity was reduced by 4.2±2.2 points, 38 patients (66.7%) had ≥50% pain relief, 69% reported functional improvement, especially in gait ability (25) and activities of daily life (14), and 46 patients (80.7%) had improved sleep quality. The starting dose of BTDS was 4.4–17.5 μg/h; maintenance dose was 8.8–70 μg/h. At the start of BTDS treatment, all patients used a total of 187 concomitant analgesics daily, 72% of which were stopped during treatment with BTDS; the number of patients that could be managed exclusively with BTDS and rescue analgesia increased to 31%. 13 patients (22%) presented nausea, eight constipation, six local skin reactions, three vomiting and somnolence, and two patients experienced dizziness. Four patients (6.9%) stopped BTDS due to adverse reactions. Conclusions: BTDS is an effective and safe alternative for the treatment of patients with severe post-traumatic pain, reducing the intensity of pain and improving functional capacity and quality of sleep.

Pharmacokinetics of buprenorphine following intravenous and intramuscular administration in male rhesus macaques (Macaca mulatta)

This study reports the pharmacokinetics of buprenorphine in conscious rhesus macaques (Macaca mulatta) after intravenous (i.v.) and intramuscular (i.m.) administration. Four healthy, opioid-naïve, socially housed, adult male macaques were used. Buprenorphine (0.03 mg/kg) was administered intravenously as a bolus or intramuscularly on separate occasions. Blood samples were collected prior to, and up to 24 h, postadministration. Serum buprenorphine concentrations were analyzed with liquid chromatography-mass spectrometry. Noncompartmental pharmacokinetic analysis was performed with commercially available software. Mean residence time in the i.v. study as compared to the i.m. study was 177 (159-189) vs. 185 (174-214) min, respectively [median (range)]. In the i.v. study, concentration back-extrapolated to time zero was found to be 33.0 (16.8-57.0) ng/mL [median (range)]. On the other hand, the maximum serum concentration found in the i.m. study was 11.8 (6.30-14.8) ng/mL [median (range)]. Rhesus macaques maintained concentrations >0.10 ng/mL for over 24 h in the i.v. study and over 12 h in the i.m. study. Bioavailability was found to be 68.1 (59.3-71.2)% [median (range)]. No significant adverse effects were observed in the monkeys at the 0.03 mg/kg dose of buprenorphine during either study.

Transdermal buprenorphine in chronic pain: indications and clinical experience

Transdermal buprenorphine has been shown to be effective in managing moderate-to-severe cancer pain and severe pain that is unresponsive to nonopioid analgesics. In clinical trials, it provided better pain relief than placebo, despite a higher consumption of rescue analgesia by placebo patients. Analgesia was rated as satisfactory or better by 90% of patients in a long-term follow-up study and 94.6% considered the buprenorphine matrix patch to be user friendly. Transdermal buprenorphine is well tolerated; most adverse events are transient local reactions to the patch or systemic effects typical of treatment with opioids. Even in opioid-experienced volunteers, buprenorphine does not cause respiratory depression at doses up to 70-times higher than those used for analgesia. No problems have been encountered when switching from another opioid to transdermal buprenorphine, or in combining the buprenorphine patch with intravenous morphine or tramadol for breakthrough pain. There is a growing body of evidence that transdermal buprenorphine may be particularly useful for managing neuropathic pain. Most notably, it appears to be effective in treating hyperalgesic states and syndromes characterized by pronounced central sensitization.

Medication pain management in the elderly: unique and underutilized analgesic treatment options

BACKGROUND

By 2030, the US population of adults aged ≥65 years will increase by >80%, and these adults will account for nearly 20% of the US population. In this population, the decline of multiple physiologic processes and diseases collectively influence treatment options. Physiologic changes, drug-drug interactions resulting from polypharmacy, and drug-disease interactions combine to make elderly patients more sensitive to the adverse events (AEs) associated with medications, all of which must be considered in drug selection.

OBJECTIVE

This article focuses on select underutilized medication options for analgesia that may provide significant advantages in the elderly population above and beyond commonly prescribed conventional choices.

METHODS

We performed a complete review of the literature using the search terms pain management, elderly, opioids, NSAIDs, topical NSAIDs, levorphanol, buprenorphine transdermal, and tapentadol. Databases searched included PubMed, Google Scholar, Ovid, and Athens. Package inserts were utilized for approval dates, indications, and formulations available. We looked at reviews of agents to identify important studies for consideration that searches may have missed. Pharmacology and pharmacokinetic data were taken from randomized trials focusing in this area. Pivotal Phase III trials were utilized for discussion of clinical trial experience and to summarize efficacy and AEs. For purposes of validity, only peer-reviewed literature was included.

RESULTS

There were limited data that specifically outlined analgesic drug selection and highlighted safer alternatives for the elderly patient based on polypharmacy risks, end-organ deterioration, and/or drug choices that presented less risk. We focused on unique opioid alternatives: levorphanol, which offers several therapeutic advantages similar to methadone but without the pharmacokinetic and drug-interaction pitfalls associated with methadone; tapentadol, associated with significantly less gastrointestinal distress and constipation; and transdermal buprenorphine, an agonist/antagonist with less risk for the toxicities associated with conventional opioids and with compliance benefits. Topical NSAIDs are discussed as a viable therapeutic option. Specific attention to a more desirable tolerability profile, including avoidance of drug interactions, end-organ dysfunction, and gastrointestinal bleed with topical NSAID agents versus their oral counterparts is discussed, including the ability to achieve superior tissue levels for appropriately selected inflammatory conditions.

CONCLUSION

It is incumbent that providers consider these options as part of an analgesic armamentarium in an effort to maximize therapeutic benefit and minimize risks in the increasing elderly patient population.

Pharmacokinetics, Tolerability, and Performance of a Novel Matrix Transdermal Delivery System of Fentanyl Relative to the Commercially Available Reservoir Formulation in Healthy Subjects

A novel transdermal formulation of fentanyl-containing dipropylene glycol droplets dispersed in a silicone matrix with a rate-controlling membrane was developed. Healthy male subjects (n = 24) received repeated 72-hour applications of fentanyl (50 mug/h) as the novel matrix and the conventional reservoir formulations in a randomized, 2-way crossover study. Blood samples were collected, and serum concentrations of fentanyl were assayed using liquid chromatography with mass spectrometry detection. The mean area under the curve (AUCtau) and peak concentrations (C(max)) of the matrix formulation were 84 838 pg.h/mL and 1680 pg/mL, respectively. Ratio and 90% confidence intervals of AUCtau and C(max) between the 2 formulations were within 80% to 125%. Adherence of the matrix formulation was higher than the reservoir formulation (62.5 vs 56.2%, P < .0001), without affecting skin irritation. Vital signs and adverse events of the 2 formulations were similar in nature and frequency. The novel matrix formulation displayed enhanced adherence and resulted in similar pharmacokinetics and tolerability as the reservoir formulation.

Efficacy and safety of transdermal buprenorphine in the management of children with cancer-related pain

BACKGROUND

The current study investigated the efficacy, safety, tolerability, and compliance of a transdermal buprenorphine delivery system for the management of chronic cancer pain in the pediatric population.

PROCEDURE

Sixteen pediatric patients with moderate to severe cancer-related pain not satisfactorily controlled with previous non-opioid therapies were enrolled. Transdermal buprenorphine was administered following a 72 hour schedule and rescue medication (tramadol) was allowed for breakthrough pain. Pain intensity was assessed using the Wong-Baker faces pain rating scale (WBS) and other parameters related to the global quality of life were evaluated. Children's evaluations of efficacy, compliance, and tolerability were recorded using numerical scales. Adverse events were monitored during the study and the medications needed to control opioid-related nausea and constipation were recorded.

RESULTS

Eleven patients (68.75%) responded to transdermal buprenorphine after 2 weeks of treatment. Pain intensity measured with WBS decreased from 6.25 at baseline to 1.38 at Day +60 (P < 0.001). All outcome measures of global quality of life (quality of sleep, alimentation, play and activity, speech, and crying) significantly improved over the 60-day study period. Children's evaluations of compliance and tolerability of the drug were always positive over the entire period of treatment. No severe adverse events were recorded. Opioid-related nausea was well controlled with medication on request, and the need for laxative therapy was greater at the end of the second month of treatment.

CONCLUSIONS

Transdermal buprenorphine was found to represent an efficient, safe and well tolerated approach to the management of children's chronic cancer pain.

Buprenorphine: the basic pharmacology revisited

The historical background leading to the current use of buprenorphine as an analgesic and its role in the management of opioid dependence is summarized. The popular description of buprenorphine as a "partial agonist" is discussed in relation to efficacy in animal models of antinociception and clinical analgesia. The latest information on the respiratory depressant effects of buprenorphine and its N-dealkylated metabolite (norbuprenorphine) is presented. New data on the buprenorphine withdrawal syndrome in rats are described.

Transdermal buprenorphine for postoperative pain control in gynecological surgery: a prospective randomized study

OBJECTIVE

Although numerous methods are available for postoperative pain (POP) management, new approaches are constantly being investigated. This feasibility study assessed the buprenorphine transdermal therapeutic system (Bup-TTS) for the treatment of POP after gynecological open surgery.

RESEARCH DESIGN AND METHODS

Forty-five patients were prospectively randomized to different Bup-TTS dosages (17.5, 35, or 52.5 μg/h). Patients were blinded with regard to patch dose.

MAIN OUTCOME MEASURES

Efficacy was evaluated in terms of rescue boluses (intravenous morphine 2 mg in the first six postoperative hours, intravenous ketorolac 30 mg thereafter) required to achieve a static and dynamic Numerical Rating Scale (sNRS and dNRS) score ≤4. Side effects were evaluated from patch application (12 hours before surgery) until the 72nd postoperative hour. Patient satisfaction regarding POP management was assessed via anonymous questionnaire.

RESULTS

All Bup-TTS groups required additional postoperative analgesia, particularly in the first postoperative hour. No between-group differences in sNRS/dNRS values were recorded at emergence from anesthesia. A significant inverse correlation occurred between Bup-TTS dosage and use of morphine (p = 0.04), ketorolac (p = 0.04) or both rescues (p = 0.02). Postoperative nausea/vomiting occurred in 3.1% of assessments, with no between-group differences and a significant correlation with morphine amount (p = 0.01). No serious side effects occurred. Despite no between-group difference, patient satisfaction was inversely correlated with the number of rescue doses (p < 0.001). Study limitations include the small sample size, the absence of a control group treated with a more conventional technique for POP relief, the focus on selected patients at low perioperative risk and the presence of slightly different types of open surgery (hysterectomy vs myomectomy only).

CONCLUSION

Bup-TTS efficacy was directly proportional to its dosage, although additional analgesia was required, particularly in the first postoperative hour. Moreover, the consumption of morphine and ketorolac was inversely correlated to the Bup-TTS dosage. Increasing Bup-TTS doses were not associated with an increased incidence of side effects. Bup-TTS appears a safe and feasible approach for moderate POP management; further larger studies are warranted.

Buprenorphine 5, 10 and 20 μg/h transdermal patch: a review of its use in the management of chronic non-malignant pain

This article reviews the pharmacology, therapeutic efficacy and tolerability profile of the 7-day lower-dose (5, 10 and 20 μg/h) buprenorphine transdermal patch (BuTrans®, Norspan®) in the management of chronic non-malignant pain, with a focus on European labelling for the drug. Buprenorphine is a semi-synthetic opioid analgesic that acts primarily as a partial agonist at the mu opioid receptor. The transdermal formulation provides continuous delivery of buprenorphine, resulting in relatively consistent plasma drug concentrations throughout the 7-day dosing interval. The analgesic efficacy of transdermal buprenorphine in patients with osteoarthritis of the hip and/or knee has been demonstrated in several randomized controlled trials, which have shown the formulation to be equivalent to sublingual buprenorphine, noninferior to prolonged-release tramadol tablets, noninferior to codeine plus paracetamol (acetaminophen) combination tablets (when transdermal buprenorphine was used together with regularly scheduled oral paracetamol) and generally superior to a matching transdermal placebo patch. Transdermal buprenorphine was significantly more effective than placebo in reducing chronic low back pain of at least moderate severity in two randomized, double-blind, crossover trials. Other clinical trials, including a randomized, double-blind, maintenance-of-analgesia study, have also demonstrated the analgesic efficacy of transdermal buprenorphine in patients with chronic non-malignant pain of various causes. In general, serious adverse events with transdermal buprenorphine are similar to those for other opioid analgesics. Transdermal buprenorphine has a ceiling effect for respiratory depression, and the main risk is when it is combined with other CNS depressants. The most frequently reported adverse events with transdermal buprenorphine are headache, dizziness, somnolence, constipation, dry mouth, nausea, vomiting, pruritus, erythema, application site pruritus and application site reactions. Transdermal buprenorphine was better tolerated than sublingual buprenorphine in a 7-week, randomized, double-blind trial in patients with osteoarthritis pain. Nevertheless, as with other opioids, persistence with transdermal buprenorphine therapy is difficult for many patients because of adverse events or other reasons. Thus, transdermal buprenorphine has generally demonstrated good efficacy and tolerability in clinical trials in chronic non-malignant pain, providing effective background analgesia as part of pain management strategies for patients with osteoarthritis, low back pain and other persistent pain syndromes of at least moderate severity. It also has favourable pharmacodynamic and pharmacokinetic properties, which have beneficial clinical implications, most notably the convenience of once-weekly administration and no need for dosage adjustments in the elderly or those with compromised renal function, making it an opioid of choice in these patients, and a useful therapeutic option overall in the management of chronic non-malignant pain.

Interaction of μ-opioid receptor agonists and antagonists with the analgesic effect of buprenorphine in mice

Buprenorphine is a potent opioid analgesic with partial agonistic properties at mu-opioid receptors. This study investigated the interaction potential with several full mu-agonists in the tail-flick test in mice. We further examined the reversibility of buprenorphine antinociception by different mu-opioid receptor antagonists. Combination of buprenorphine with morphine, oxycodone, hydromorphone and fentanyl in the analgesic dose range resulted in additive or synergistic effects. When given after the decline of the acute buprenorphine effect, both morphine and fentanyl also showed full efficacy. A moderate antagonistic effect according to the partial mu-agonistic properties of buprenorphine was only seen when high doses exceeding the therapeutic dose ranges were combined. Under these conditions antinociception of morphine was reduced to the effect of buprenorphine alone. Prophylactic administration of naloxone (10 mg/kg i.v.), naltrexone (1 mg/kg i.v.) and clocinnamox (5 mg/kg s.c.) fully and persistently blocked the antinociception of a high dose of buprenorphine. An established effect of buprenorphine was less sensitive, although repeated administration of naloxone induced complete antagonism, as did the irreversible antagonist clocinnamox under prophylactic and curative treatment conditions. Our results suggest that the antinociceptive effect of buprenorphine is mainly, if not exclusively, mediated by activation of mu-opioid receptors. They confirm clinical experience that in the analgesic dose range a switch between buprenorphine and full mu-agonists is possible without loss of analgesic efficacy and without a refractory period between the termination of buprenorphine analgesia and the onset of action of the new mu-opioid treatment. Antinociception of buprenorphine is sensitive towards mu-opioid receptor antagonists and incomplete inhibition can be improved by increasing the dose or repetitive dosing.

In-vitro and in-vivo transdermal iontophoretic delivery of tramadol, a centrally acting analgesic

Objectives

The feasibility of transdermal delivery of tramadol, a centrally acting analgesic, by anodal iontophoresis using Ag/AgCl electrodes was investigated in vitro and in vivo.

Methods

To examine the effect of species variation and current strength on skin permeability of tramadol, in-vitro skin permeation studies were performed using porcine ear skin, guinea-pig abdominal skin and hairless mouse abdominal skin as the membrane. In an in-vivo pharmacokinetic study, an iontophoretic patch system was applied to the abdominal skin of conscious guinea pigs with a constant current supply (250 µA/cm2) for 6 h. An intravenous injection group to determine the pharmacokinetic parameters for estimation of the transdermal absorption rate in guinea pigs was also included.

Key findings

The in-vitro steady-state skin permeation flux of tramadol current-dependently increased without significant differences among the three different skin types. In the in-vivo pharmacokinetic study, plasma concentrations of tramadol steadily increased and reached steady state (336 ng/ml) 3 h after initiation of current supply, and the in-vivo steady-state transdermal absorption rate was 499 µg/cm2 per h as calculated by a constrained numeric deconvolution method.

Conclusions

The present study reveals that anodal iontophoresis provides current-controlled transdermal delivery of tramadol without significant interspecies differences, and enables the delivery of therapeutic amounts of tramadol.