Comparison of Oxycodone Pharmacokinetics after Buccal and Sublingual Administration in Children

Population pharmacokinetics of oxycodone: Premature neonates to adults

BACKGROUND

Oxycodone is used in children and adults for the control of acute postoperative pain. Covariate influences such as age, size, and fat mass on oxycodone pharmacokinetic parameters over the human lifespan are poorly quantified.

METHODS

Pooled oxycodone time-concentration profiles were available from preterm neonates to adults. Data from intravenous, intramuscular, buccal, and epidural formulations were analyzed using nonlinear mixed-effects models. Normal fat mass was used to determine the influence of fat on oxycodone pharmacokinetics. Theory-based allometry was used to scale pharmacokinetic parameters to a 70 kg individual. A maturation function described the increase in clearance in neonates and infants.

RESULTS

There were 237 subjects (24 weeks postmenstrual age to 75 years; 0.44-110 kg) providing 1317 plasma concentrations. A three-compartment model with first-order elimination best described oxycodone disposition. Population parameter estimates were clearance (CL) 48.6 L.h^-1 .70 kg^-1 (CV 71%); intercompartmental clearances (Q2) 220 L.h^-1 .70 kg^-1 (CV 64%); Q3 1.45 L.h^-1 .70 kg^-1 ; volume of distribution in the central compartment (V1) 98.2 L.70 kg^-1 (CV 76%); rapidly equilibrating peripheral compartment (V2) 90.1 L. 70 kg^-1 (CV 76%); slow equilibrating peripheral compartment (V3) 28.9 L.70 kg^-1 . Total body weight was the best size descriptor for clearances and volumes. Absorption halftimes (T_ABS ) were: 1.1 minutes for intramuscular, 70 minutes for epidural, 82 minutes for nasogastric, and 159.6 minutes for buccal administration routes. The relative bioavailability after nasogastric administration was 0.673 with a lag time of 8.7 minutes.

CONCLUSIONS

Clearance matured with age; 8% of the typical adult value at 24 weeks postmenstrual age, 33% in a term neonate and reached 90% of the adult clearance value by the end of the first year of life. Allometric scaling using total body weight was the better size descriptor of oxycodone clearance than fat-free mass.

A Novel Bioanalytical Method for the Determination of Opioids in Blood and Pericardial Fluid

Opioids are the drugs most commonly detected in overdose deaths and the second most consumed worldwide. An analytical methodology has been optimized and fully validated for the determination of codeine, morphine, 6-acetylmorphine, 6-acetylcodeine, oxycodone, oxymorphone and fentanyl in whole blood and pericardial fluid. The internal standards used were codeine-d3, morphine-d3, 6-acetylmorphine-d3 and fentanyl-d5. Before solid-phase extraction, volumes of 250 μL of blood and pericardial fluid were subjected to a protein precipitation (with 750 μL of ice-cold acetonitrile) and a microwave-induced oximation was performed using a solution of 1% aqueous hydroxylamine hydrochloride in phosphate-buffered saline (1:2, v/v). Finally, the dried extracts were further derivatized with a solution of n-methyl-n-(trimethylsilyl) trifluoroacetamide + 5% trimethylchlorosilane under microwave irradiation. The chromatographic analysis was carried out using gas chromatography–mass spectrometry operating in electron impact and selected ion monitoring mode. For all analytes, the method was linear between 5 and 1,000 ng/mL with determination coefficients (r2) >0.99. Depending on the analyte and matrix, the limit of detection varies between 3 and 4 ng/mL. Intra- and intermediate precision (<20%) and bias (±20%) were acceptable for all analytes in both matrices. The stability of the substances in the studied matrices was guaranteed, at least, 24 h in the autosampler, 4 h at room temperature and 30 days after three freeze/thaw cycles. This methodology was applied to real samples from the Laboratory of Chemistry and Forensic Toxicology, Centre Branch, of the National Institute of Legal Medicine and Forensic Sciences, Portugal.

Why Are the Majority of Active Compounds in the CNS Domain Natural Products? A Critical Analysis

Small-molecule natural products (NPs) have a long and successful track record of providing first-in-class drugs and pharmacophore (scaffolds) in all therapeutic areas, serving as a bridge between modern and traditional medicine. This trajectory has been remarkably successful in three key areas of modern therapeutics: cancers, infections, and CNS diseases. Beginning with the discovery of morphine 200 years ago, natural products have remained the primary source of new drugs/scaffolds for CNS diseases. In this perspective, we address the question: why are the majority of active compounds in the CNS domain natural products? Our analysis indicates that ∼84% approved drugs for CNS diseases are NPs or NP-inspired, and interestingly, 20 natural products provided more than 400 clinically approved CNS drugs. We have discussed unique physicochemical properties of NPs and NP-inspired vis-à-vis synthetic drugs, isoform selectivity, and evolutionary relationship, providing a rationale for increasing focus on natural product driven discovery for next-generation drugs for neurodegenerative diseases.

The analgesic efficacy and pharmacokinetics of epidural oxycodone after gynaecological laparotomy: a randomized, double-blind, double-dummy comparison with intravenous administration

AIM

The aim of the present study was to compare the analgesic efficacy of epidural and intravenous (i.v.) oxycodone at the same dose.

METHODS

In this randomized, double-blind, double-dummy clinical trial, 30 women, aged 24-67 years, undergoing elective gynaecological laparotomy, were administrated either i.v. saline and epidural oxycodone 0.1 mg·kg^-1 (EPI group; n = 15) or i.v. oxycodone 0.1 mg·kg^-1 and epidural saline (IV group; n = 15). For multimodal analgesia, patients received i.v. paracetamol and dexketoprofen, and a triple-mixture epidural infusion after the first 4 h postoperatively. The primary outcome was the total dose of i.v. fentanyl for rescue analgesia during the first 4 h postoperatively.

RESULTS

All patients required fentanyl during the first 4 h. The median number of fentanyl doses were three (quartiles 1, 8) in the EPI group and seven (6, 9) in the IV group (mean difference 3.1; 95% confidence interval 0.9, 5.2; P = 0.01). After the first 4 h, the two groups needed a similar total dose of epidural infusion. Patient satisfaction was similarly high in both groups, and both administration routes were well tolerated.

CONCLUSIONS

The data support the superiority of epidural oxycodone compared with that of i.v. administration in pain management after laparotomy.

Absorption of ibuprofen orodispersible tablets in early postoperative phase - a pharmacokinetic study

OBJECTIVE

Patient-controlled oral analgesia has gained popularity in postoperative pain management. Anesthesia and surgery delay gastrointestinal tract function and this may therefore decrease bioavailability of drugs taken by mouth. To hasten absorption, an orodispersible ibuprofen tablet has been developed. In this study, we evaluated the pharmacokinetics and feasibility of orodispersible ibuprofen tablets in spine surgery patients.

METHODS

The study design was a prospective clinical trial where each patient served as her/his own control. Fifteen patients aged 19-75 years were given two orodispersible ibuprofen 200 mg tablets the day before surgery and two more tablets immediately after surgery. Blood samples for ibuprofen concentrations were taken at intervals for 6 hours following pre- and postsurgical administration of ibuprofen.

RESULTS

The mean preoperative area under time-concentration curve for ibuprofen (AUC_0-360) was 4806 (SD 1104) min·mg/L, and after surgery it was 2141 (583) min·mg/L (mean difference 2664, 95% CI for difference 2003 to 3325, p < .001). The mean of the maximum preoperative plasma concentration of ibuprofen was three times higher, 26.7 (7.7) mg/L, than the postoperative value of 8.6 (2.1) mg/L (mean diff. 18.1, 95% CI 13.9 to 22.4, p < .001). Times to maximum concentration were similar pre- and postoperatively at 155 (58) minutes and 169 (113) minutes (p = .67). No serious or unexpected adverse events were recorded.

CONCLUSIONS

While orodispersible ibuprofen tablets were feasible, ibuprofen absorption decreased immediately after surgery compared to the day before surgery. Thus, further studies are needed to establish the adequate initial postoperative dose.

Pharmacokinetics, pharmacodynamics and pharmacogenetics associated with nonsteroidal anti-inflammatory drugs and opioids in pediatric cancer patients

INTRODUCTION

Advancing appropriate and adequate analgesic pharmacotherapy in pediatric patients with cancer is an area of clinical need. Few studies have been performed to evaluate the selection of an analgesic and appropriate dosing corresponding to analgesic effect among pediatric cancer patients. This review describes information related to pharmacokinetic, pharmacodynamic, and pharmacogenomic (when applicable) considerations for analgesics that are commonly used to manage pain experienced by pediatric patients with cancer. Areas covered: Analgesics commonly used to treat pediatric patients with malignancy patterned after the World Health Organization's 'analgesic ladder' for cancer pain management. Expert opinion: Addressing pain management safely and effectively in pediatric patients with cancer will require advances in both drug development, to increase the armament of analgesics available for children, and our pharmacologic understanding of those analgesics in current use. However, performing the necessary types of studies to develop new analgesics, or gain knowledge of existing therapy, within a population that is relatively small, diverse, and who experience pain originating from a variety of sources, is a tremendous challenge.

Maturation of oxycodone pharmacokinetics in neonates and infants: Oxycodone and its metabolites in plasma and urine

AIMS

This study aimed to characterize the pharmacokinetics of oxycodone and its major metabolites in infants and covered the age range between extremely preterm neonates and 2-year-old infants.

METHODS

Seventy-nine infants (gestational age 23-42 weeks; postnatal age 0-650 days) received intravenous oxycodone hydrochloride trihydrate at a dose of 0.1 mg kg^-1 during or after surgery. Three to seven blood samples were taken from each infant, and plasma concentrations of oxycodone, noroxycodone, oxymorphone, and noroxymorphone were quantified. The unconjugated forms of these compounds were determined in urine collected after up to 24 or 48 h from 25 infants. Pharmacokinetics was determined using noncompartmental analysis and reported for six clinically relevant age groups based on postmenstrual age.

RESULTS

Oxycodone pharmacokinetics changed markedly with patient age. Preterm neonates were found to have the highest pharmacokinetic variability out of the study population. In extremely preterm neonates (n = 6) median of elimination half-life was 8.8 h (range 6.8-12.5), in preterm (n = 11) 7.4 h (4.2-11.6), and in older neonates (n = 22) 4.1 h (2.4-5.8), all of which were significantly longer than that in infants aged 6-24 months (n = 12) 2.0 h (1.7-2.6). Median renal clearance was fairly constant in all age groups, whereas non-renal clearance markedly increased with age. Noroxycodone was the major metabolite in plasma and urine.

CONCLUSIONS

Oxycodone elimination is slower and pharmacokinetic variability more pronounced in neonates when compared to older infants. These findings highlight the importance of careful dose titration for neonates.

Sufentanil sublingual formulation for the treatment of acute, moderate to severe postoperative pain in adult patients

INTRODUCTION

Sufentanil is a highly selective µ-opioid agonist commonly used by intravenous and intrathecal routes for acute pain. Sublingual sufentanil formulation for patient controlled analgesia (PCA) uses an innovative administration device that suspends a 15 µg nanotablet with a fixed lockout interval. The system is a non-invasive, less burdensome method of opioid delivery compared to intravenous and intrathecal routes. Sublingual nanotablet PCA transmucosal bioavailability is 59% and the meaningful analgesic onset time is 60 minutes. Areas covered: This paper focuses on the effectiveness, safety and feasibility of sufentanil PCA sublingual formulation for the management of postoperative pain. The paper is based on PubMed searches and the European Medicine Agency assessment report. Expert commentary: Under-treatment of acute pain is a substantial clinical problem. The initial experiences with the sublingual delivery system are encouraging. Sufentanil sublingual nanotablets intended for PCA device use are approved in Europe, and approval is pending in the United States.

Anesthesiological considerations for children with obstructive sleep apnea

PURPOSE OF REVIEW

To summarize recent evidence-based data regarding outcomes associated with children who have obstructive sleep apnea (OSA).

RECENT FINDINGS

Internet surveys conducted by pediatric otolaryngologists and pediatric anesthesiologists have reported a disturbing number of deaths within 24 h of tonsillectomy attributed to postsurgical/anesthesia apnea. Several occurred in the post anesthesia care unit after routine monitors had been removed. In addition, a number of deaths also have been attributed to children who have duplicated cytochromes allowing the rapid conversion of codeine to morphine, thus producing a relative drug overdose. Finally, there is some human and animal evidence suggesting that repeated episodes of hypoxemia result in altered opioid receptors causing relative opioid sensitivity. These factors have important clinical implications.

SUMMARY

Perioperative deaths in children with OSA occur at a low frequency. Hypoxia-induced opioid sensitivity combined with an approximate 1-2% incidence of rapid conversion of codeine to morphine suggest the need for new approaches for providing preoperative assessment of risk, extended postoperative observation and the need for alternative opioids to codeine. Additionally, new less painful surgical approaches may help to reduce postoperative opioid requirements and therefore perhaps less risk for opiate-induced apnea in this vulnerable population.

Alternative routes to oral opioid administration in palliative care: a review and clinical summary

OBJECTIVE

A major goal of palliative care is to provide comfort, and pain is one of the most common causes of treatable suffering in patients with advanced disease. Opioids are indispensable for pain management in palliative care and can usually be provided by the oral route, which is safe, effective, and of lowest cost in most cases. As patients near the end of life, however, the need for alternate routes of medication increases with up to 70% of patients requiring a nonoral route for opioid administration. In order to optimize patient care, it is imperative that clinicians understand existing available options of opioid administration and their respective advantages and disadvantages.

METHODS

We performed a literature review to describe the most commonly used and available routes that can substitute for oral opioid therapy and to provide a summary of factors affecting choice of opioid for use in palliative care in terms of benefits, indications, cautions, and general considerations.

RESULTS

Clinical circumstances will largely dictate appropriateness of the route selected. When the oral route is unavailable, subcutaneous, intravenous, and enteral routes are preferred in the palliative care population. The evidence supporting sublingual, buccal, rectal, and transdermal gel routes is mixed.

CONCLUSIONS

This review is not designed to be a critical appraisal of the quality of current evidence; rather, it is a summation of that evidence and of current clinical practices regarding alternate routes of opioid administration. In doing so, the overarching goal of this review is to support more informed clinical decision making.

Intravenous oxycodone for pain relief in the first stage of labour--maternal pharmacokinetics and neonatal exposure

Physiological changes during pregnancy may change pharmacokinetics of compounds. Oxycodone is an increasingly used opioid agonist in acute pain management but its pharmacokinetics in labouring women has not been established. We studied the maternal pharmacokinetics and neonatal exposure of intravenous oxycodone for pain relief in the first stage of labour. The study was prospective, open-labelled and with a control group. After informed consent, 15 nulliparous parturients and newborns, and newborns in a control group were studied. In the study group, oxycodone boluses of 1 mg i.v., up to a cumulative dose of 5 mg, was administered when labour pain score was 5/10 or higher. As the control group, 30 other newborns after uncomplicated deliveries with no systemic opioids were assessed for the neonatal outcome. In the study group, maternal pharmacokinetics of oxycodone was measured from plasma concentrations during labour, and neonatal exposure was assessed from umbilical plasma samples using population pharmacokinetic methods. Maternal plasma oxycodone concentration decreased with a median half-life of 2.6 hr (range, 1.8-2.8). Oxycodone concentrations in the umbilical plasma 2.7 μg/l (0.3-14.5) were similar as in maternal plasma 2.4 (0.1-14.8) μg/l at the time of birth. No severe or unexpected adverse effects were noted. To conclude, firstly, maternal elimination half-life of i.v. oxycodone was significantly shorter than that reported in non-pregnant women, and secondly, maternal plasma oxycodone at the birth correlated well with neonatal umbilical concentrations and may, thus, be used as an estimate of neonatal exposure.

Metabolism of oxycodone in human hepatocytes from different age groups and prediction of hepatic plasma clearance

Oxycodone is commonly used to treat severe pain in adults and children. It is extensively metabolized in the liver in adults, but the maturation of metabolism is not well understood. Our aim was to study the metabolism of oxycodone in cryopreserved human hepatocytes from different age groups (3 days, 2 and 5  months, 4  years, adult pool) and predict hepatic plasma clearance of oxycodone using these data. Oxycodone (0.1, 1, and 10 μM) was incubated with hepatocytes for 4 h, and 1 μM oxycodone also with CYP3A inhibitor ketoconazole (1 μM). Oxycodone and noroxycodone concentrations were determined at several time points with liquid chromatography-mass spectrometry. In vitro clearance of oxycodone was used to predict hepatic plasma clearance, using the well-stirred model and published physiological parameters. Noroxycodone was the major metabolite in all batches and ketoconazole inhibited the metabolism markedly in most cases. A clear correlation between in vitro oxycodone clearance and CYP3A4 activity was observed. The predicted hepatic plasma clearances were typically much lower than the published median total plasma clearance from pharmacokinetic studies. The data suggests that there are no children-specific metabolites of oxycodone. Moreover, CYP3A activity seems to be the major determinant in metabolic clearance of oxycodone regardless of age group or individual variability in hepatocyte batches.

Effect of absorption site on the pharmacokinetics of sublingual asenapine in healthy male subjects

Asenapine is a psychopharmacologic agent approved in the United States for the acute treatment of schizophrenia in adults and the acute treatment of manic or mixed episodes associated with bipolar I disorder with or without psychotic features in adults. It is pending approval for the treatment of schizophrenia and manic episodes associated with bipolar I disorder in Europe. Asenapine is administered as a sublingual formulation. To determine whether the pharmacokinetics of asenapine are impacted by placing the tablet buccally ('cheeking') or allowing the tablet to dissolve on the top of the tongue, pharmacokinetics were compared following buccal and supralingual administration versus sublingual administration. In this open-label, randomized, 3-way crossover trial, healthy men (n=36) received single 5 mg doses of asenapine via sublingual, supralingual and buccal routes, at least 1 week apart. With buccal administration, the area under the concentration-over-time curve (AUC(0-infinity)) and peak concentration (C(max)) were, respectively, 24%, and 19% higher than with sublingual administration; these routes were not bioequivalent. With supralingual administration, AUC(0-infinity) and C(max) were 6% and 13% lower than with sublingual administration; bioequivalence was established based on AUC(0-infinity) only; bioequivalence based on C(max) could not be assessed due to 40% within-subject variability. The most common adverse events were oral paresthesia (sublingual, 75.8%; supralingual, 55.9%; buccal, 45.7%) and somnolence (81.8%; 76.5%; 68.6%). Compared with the recommended sublingual route of asenapine administration, exposure was 24% higher with buccal administration and comparable to supralingual administration. However, differences in exposure associated with variable placement in the oral cavity did not compromise safety in healthy subjects.

Off-label and unlicensed drug prescribing in three paediatric wards in Finland and review of the international literature

OBJECTIVES

In paediatric pharmacotherapy, many drugs are prescribed to be given in ways and for conditions not approved in the marketing authorization (MA). Thus, off-label prescribing of drugs with no MA is widespread in paediatric wards. However, drug MA status and clinical practices differ across countries. In this prospective study, we studied the prescribing of off-label and unlicensed drugs in three paediatric wards in a tertiary hospital in Finland. Furthermore, we reviewed previous published studies to provide an up-to-date international perspective on prescribing of off-label and unlicensed drugs for hospitalized children.

METHODS

During a 2-week period, prescriptions for patients under 18 years of age (median age 1*6 years) in three wards; neonatal intensive care unit (NICU), general paediatric ward and paediatric surgical ward were recorded daily and drug-licensing status of all prescriptions was determined according to the approved summary of product characteristics. Published studies were retrieved through electronic searches, including MEDLINE (PubMed).

RESULTS

Of the 141 children, 108 received 629 prescriptions. Of the 108 children with a prescription, 82 (76%) had at least one off-label or unlicensed drug prescribed; 79% in the NICU, 63% in the general ward and 91% in the surgical ward (P = 0*014). Of the 108 children with a prescription, 26 (24%) received prescriptions for licensed drugs, 71 (66%) received prescriptions off-label and 36 (33%) for unlicensed drugs. Of all 629 prescriptions, 321 (51%) were for licensed drugs, 226 (36%) for off-label and 82 (13%) for unlicensed drugs. International studies showed similar extents of off-label and unlicensed-drug prescribing.

CONCLUSION

This study indicates that the use of off-label and unlicensed drugs is widespread in all the different paediatric wards surveyed and was as extensive as those reported for other countries.

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.

Endogenous opiates and behavior: 2006

This paper is the 29th consecutive installment of the annual review of research concerning the endogenous opioid system, now spanning 30 years of research. It summarizes papers published during 2006 that studied the behavioral effects of molecular, pharmacological and genetic manipulation of opioid peptides, opioid receptors, opioid agonists and opioid antagonists. The particular topics that continue to be covered include the molecular-biochemical effects and neurochemical localization studies of endogenous opioids and their receptors related to behavior (Section 2), and the roles of these opioid peptides and receptors in pain and analgesia (Section 3); stress and social status (Section 4); tolerance and dependence (Section 5); learning and memory (Section 6); eating and drinking (Section 7); alcohol and drugs of abuse (Section 8); sexual activity and hormones, pregnancy, development and endocrinology (Section 9); mental illness and mood (Section 10); seizures and neurological disorders (Section 11); electrical-related activity and neurophysiology (Section 12); general activity and locomotion (Section 13); gastrointestinal, renal and hepatic functions (Section 14); cardiovascular responses (Section 15); respiration and thermoregulation (Section 16); and immunological responses (Section 17).

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.

Ensuring pain relief for children at the end of life

Pain management in the context of pediatric palliative care can be challenging. The present article reviews, through a case-based presentation, the nonpharmacological and pharmacological methods used to ensure adequate pain control in children facing end of life. Details on the impressive range of opioid dosages required and routes of administration are highlighted from published literature and clinical experience. Where available, evidence-based recommendations are provided. Potential side effects of pain medication and barriers to good pain control are discussed. Novel analgesics and innovative delivery methods are presented as future tools enhancing pain relief at the end of life. Some challenges to ethically grounded research in this important context of care are reviewed.