Acupuncture and laserpuncture as a therapeutic approach for nociception and inflammation: An experimental study in mice.

Inflammation and pain are consequences of injuries or diseases that affect a large number of people. This study aims to evaluate the effect of acupuncture and laserpuncture on nociception and inflammation in mice compared to the effects of morphine and dexamethasone. 140 male Swiss mice were used. Treatment with acupuncture and laserpuncture were performed at the acupoints LI11, ST36, GB34, and BL60 in mice. To evaluate the effect of acupuncture and laserpuncture on nociception, the hot plate test and intraplantar formalin injection were used. The effect of acupuncture and laserpuncture on the inflammation was evaluated through carrageenan-induced paw edema. Thermographic analysis was also applied to evaluate the anti-inflammatory effects. An antinociceptive effect (≈57%) was observed in treatments with acupuncture and laserpuncture, equivalent to the effect of morphine. Laserpuncture and acupuncture decreased paw edema by ≈25%. Acupuncture had an effect equivalent to dexamethason, basides reducing the neurogenic phase by 35% and the inflammatory phase in formalin-induced nociception by 40%, equivalent to the effects of morphine. In thermographic analysis, acupuncture, laserpuncture, morphine, and negative control had paw temperature of ≈27 °C, while formalin treatment was 31°C. Acupuncture and laserpuncture proved to be effective therapies for the treatment of inflammatory and painful processes.

Comparison of the Centers for Disease Control (CDC) recommendations and the risk index for overdose or serious opioid-induced respiratory depression (RIOSORD) tool for guiding naloxone coprescribing.

PURPOSE: Patients treated with ongoing opioid therapy may be at an increased risk of respiratory depression or death, which may be mitigated through prompt administration of naloxone. The Centers for Disease Control (CDC) guidelines for prescribing opioids in primary care settings recommend patients treated with ongoing opioid analgesic therapy be offered a coprescription of naloxone based on total oral morphine milligram equivalents per day or concurrent benzodiazepine therapy. Opioid overdose risk is dose-dependent, yet other patient-specific factors contribute to this risk. The risk index for overdose or serious opioid-induced respiratory depression (RIOSORD) incorporates additional risk factors to assess the risk of overdose or clinically relevant respiratory depression. OBJECTIVES: This study compared the frequency of meeting CDC, Veterans' Health Administration (VA) RIOSORD, or civilian RIOSORD criteria for naloxone coprescribing. METHODS: A retrospective chart review of 42 Federally Qualified Health Centers in Illinois was conducted for all CII-CIV opioid analgesic prescriptions. Ongoing opioid therapy was defined as patients who received seven or more CII-CIV opioid analgesic prescriptions during the 1-year study period. Patients aged 18-89, receiving opioids for nonmalignant pain, and meeting the criteria of ongoing opioid therapy were included in the analysis. RESULTS: A total of 41,777 controlled substance analgesic prescriptions were prescribed during the study period. Data from 651 individual patient charts were evaluated. Of those, 606 patients met inclusion criteria. From these data, 57.9 percent of patients (N = 351) met civilian RIOSORD criteria, 36.5 percent (N = 221) met VA RIOSORD criteria, and 22.8 percent (N = 138) met CDC guideline recommendations for naloxone coprescribing. The percentage of patients who met RIOSORD criteria compared to CDC criteria was significantly higher (p < 0.001). Of all patients meeting ongoing opioid therapy criteria, only seven had been coprescribed naloxone. CONCLUSION: Coprescribing of naloxone is significantly underutilized in patients treated with opioid therapy for nonmalignant chronic pain and should not solely be based on total oral morphine milligram equivalents per day or concurrent benzodiazepine therapy. As risk assessment improves, consideration of other risk-conferring variables, such as gabapentinoids, skeletal muscle relaxants, and sleep hypnotics, should be considered.

Chemical composition and antinociceptive and anti-inflammatory activity of the essential oil of Hyptis crenata Pohl ex Benth. from the Brazilian Amazon.

ETHNOPHARMACOLOGICAL RELEVANCE: The leaf tea of Hyptis crenata has its practical use in the Brazilian Amazon for treating gastrointestinal and liver disorders, sweating induction, and as an anti-inflammatory. AIM OF THE STUDY: Evaluation of the chemical composition, acute oral toxicity, and antinociceptive and anti-inflammatory activities of the H. crenata essential oil. MATERIAL AND METHODS: The essential oil was hydrodistilled and analyzed by GC and GC-MS. The antinociceptive action in mice was evaluated for the peripheral and central analgesic activity (abdominal contortion and hot plate tests), and the xylene-induced ear swelling was carried out for the nociception test. RESULTS: Oxygenated monoterpenes (53.0%) and monoterpene hydrocarbons (38.9%) predominated in the H. crenata oil, being 1,8-cineo1e (35.9%), α-pinene (20.8%), camphor (10.0%), and ß-pinene (7.3%) their primary constituents. The oral oil administration in the mice did not display changes in behavior patterns or animal mortality at 300 and 2000 mg/kg doses. The control group's biochemical parameters (ALP, AST, ALT) displayed a statistical difference from the treated group, unlike the renal parameters, which showed no variation between the groups. Oil reduced the abdominal contortions at doses of 100 (79.5%) and 300 mg/kg (44.4%), while with endodontacin, the dose was 5 mg/kg (75.2%). In addition, the oil could not decrease the paw licking/biting time at doses of 30, 100, and 300 mg/kg. However, it showed a significant antinociceptive effect on the second phase in the formalin test inhibiting licking time, with a reduction of 50.8% (30 mg/kg), 63.4% (100 mg/kg), 58.0% (300 mg/kg), and morphine (4 mg/kg, 78.3%). The oil administration produced significant inhibition of ear edema at all tested doses, with a better effect produced at 30 mg/kg (64.0% inhibition). CONCLUSION: The oil of Hyptis crenata, rich in 1,8-cineole, camphor, α-pinene, and ß-pinene, totaling 74%, displayed low acute toxicity and significant anti-inflammatory activity, with peripheral and no central antinociceptive action. Thus, these results show an actual perspective on using H. crenata oil in developing a phytotherapeutic product.

Pharmacokinetics, adverse effects and effects on thermal nociception following administration of three doses of codeine to horses.

BACKGROUND: In humans, codeine is a commonly prescribed analgesic that produces its therapeutic effect largely through metabolism to morphine. In some species, analgesic effects of morphine have also been attributed to the morphine-6-glucuronide (M6G) metabolite. Although an effective analgesic, administration of morphine to horses produces dose-dependent neuroexcitation at therapeutic doses. Oral administration of codeine at a dose of 0.6 mg/kg has been shown to generate morphine and M6G concentrations comparable to that observed following administration of clinically effective doses of morphine, without the concomitant adverse effects observed with morphine administration. Based on these results, it was hypothesized that codeine administration would provide effective analgesia with decreased adverse excitatory effects compared to morphine. Seven horses received a single oral dose of saline or 0.3, 0.6 or 1.2 mg/kg codeine or 0.2 mg/kg morphine IV (positive control) in a randomized balanced 5-way cross-over design. Blood samples were collected up to 72 hours post administration, codeine, codeine 6-glucuronide, norcodeine morphine, morphine 3-glucuronide and M6G concentrations determined by liquid chromatography- mass spectrometry and pharmacokinetic analysis performed. Pre- and post-drug related behavior, locomotor activity, heart rate and gastrointestinal borborygmi were recorded. Response to noxious stimuli was evaluated by determining thermal threshold latency. RESULTS: Morphine concentrations were highest in the morphine dose group at all times post administration, however, M6G concentrations were significantly higher in all the codeine dose groups compared to the morphine group starting at 1 hour post drug administration and up to 72-hours in the 1.2 mg/kg group. With the exception of one horse that exhibited signs of colic following administration of 0.3 and 0.6 mg/kg, codeine administration was well tolerated. Morphine administration, led to signs of agitation, tremors and excitation. There was not a significant effect on thermal nociception in any of the dose groups studied. CONCLUSIONS: The current study describes the metabolic profile and pharmacokinetics of codeine in horses and provides information that can be utilized in the design of future studies to understand the anti-nociceptive and analgesic effects of opioids in this species with the goal of promoting judicious and safe use of this important class of drugs.

Neurological excitation in a 6-week-old male infant after morphine overdose.

While respiratory depression is a known complication of morphine overdose, the neuro-excitatory side effect of the morphine metabolite morphine-3-glucuronide is less widely known. Here, we report the case of an infant with neurological excitation after morphine overdose. The neuro-excitation in this infant was probably induced by an elevated morphine-3-glucuronide concentration.

Morphine Use in the Treatment of Acute Cardiogenic Pulmonary Edema and Its Effects on Patient Outcome: A Systematic Review.

PURPOSE OF REVIEW: To analyze whether the use of morphine, as initial treatment in acute cardiogenic pulmonary edema (ACPE), has an impact in clinical outcomes and mortality. A systematic review of the literature was performed, including all the studies comparing clinical outcomes in patients with ACPE who were treated or not with morphine. RECENT FINDINGS: Seven studies were selected, none of which were a randomized trial focused on answering the aim of this systematic review. The studies consisted of clinical trial secondary analysis assessing non-invasive ventilation in ACPE, one open non-randomized trial, two propensity score evaluations from large registries, and three clinical case reviews. Most of the studies showed unfavorable results with the use of morphine in terms of adverse events and mortality, and many of them were statistically significant. Finally, the ongoing MIdazolam versus MOrphine in acute cardiogenic pulmonary edema (MIMO) trial was specifically designed to compare the results of morphine use versus midazolam. The potential hemodynamic and sedative benefit of the use of morphine for vasodilatation and dyspnea amelioration may be opposed by an increase in mortality, ICU admission, and adverse events. Until there is a randomized clinical trial, the use of morphine for ACPE should be limited.

Adverse immune reactions and non-immune medications for perioperative use. / Reacciones adversas inmunitarias y no inmunitarias a fármacos de uso perioperatorio.

Reactions to medications can occur through a mechanism mediated by immunoglobulin or otherwise, not both. Drug allergy is a type of adverse reaction to the drug and comprises a range of hypersensitivity reactions mediated by different immunological mechanisms with diverse clinical manifestations. A rate of 3.2 fatal cases of anaphylaxis associated with drugs per 100,000 inhabitants per year is estimated, which seems to be approximately 10 times higher in hospitalized patients. The incidence of perioperative anaphylactic reactions is estimated at 1 in 10,000-20,000 anesthetic procedures. The diagnosis is based on a careful clinical history and physical examination. In some cases, skin tests, progressive challenges and methods to induce tolerance to the medication may be required. In hospitalized patients and at perioperative intervals, muscle relaxants, neuroleptics and morphinomimetics are frequently used and adverse reactions may occur to these drugs. This review shows a general description of the reactions of these medications, emphasizes allergic reactions and analyzes strategies for the diagnosis and treatment of these reactions.

Las reacciones a medicamentos pueden ocurrir por mecanismos mediados o no por imunoglobulina E. La alergia a fármacos es un tipo de interacción adversa y comprende una gama de reacciones de hipersensibilidad mediadas por distintos mecanismos inmunológicos con diversas manifestaciones clínicas. Se estima una tasa anual de 3.2 casos fatales de anafilaxia asociados con los fármacos por cada 100 000 habitantes, que parece ser aproximadamente 10 veces mayor en los pacientes hospitalizados. La incidencia de reacciones anafilácticas perioperatorias se estima en uno de cada 10 000-20 000 procedimientos anestésicos. El diagnóstico se basa en una cuidadosa historia clínica y en el examen físico. En algunos casos pueden requerirse pruebas cutáneas, pruebas de retos progresivos y procedimientos de inducción de tolerancia al medicamento. En los pacientes hospitalizados y en el intervalo perioperatorio frecuentemente se emplean relajantes musculares, neurolépticos y morfinomiméticos, por lo que pueden presentarse respuestas adversas a estos fármacos. En esta revisión se hace énfasis en las reacciones alérgicas a los medicamentos y se abordan estrategias para su diagnóstico y manejo.

Characteristics of opioid-maintained clients smoking fentanyl patches: The importance of confirmatory drug analysis illustrated by a case series and mini-review.

The increase in opioid prescribing in many European countries over the last decade has raised concerns about associated diversion, overdose, and mortality. Fentanyl is one of these synthetic opioids that is typically prescribed as a transdermal patch for pain that requires continuous pain relief and has been the focus of investigation due to reports of overdose and death. We report a case series of 14 drug addiction treatment entrants, who entered treatment in a service located in the region of Southern Denmark from August 2015 to December 2015 for smoking fentanyl patches. Clients presented with difficulties breathing and pains in the lungs. The clients had a history of past opioid use, including heroin. Relapses resulted in treatment disengagement. Immunoassays for fentanyl were used in the service. In some cases, false negative results occurred. Clients' urine samples were subsequently analysed in a collaborating laboratory. Seven clients tested positive for fentanyl. One client was positive for both fentanyl and heroin. Analyses were also positive for other opioids and metabolites in 6 clients, predominantly codeine and oxycodone. Results from confirmatory analysis contributed to clearer insights into clients' drug histories, which facilitated personalised care plans consisting of opioid agonist therapy informed by confirmed drug use. In Denmark, prescription levels of fentanyl are high, which has been accompanied by observations of diversion and smoking in a smaller population. In addition to revision of inappropriate prescribing to reduce diversion, we recommend increased reliance upon confirmatory drug analysis in the addiction treatment sector in Denmark.

Morphine-induced hyperalgesia involves mu opioid receptors and the metabolite morphine-3-glucuronide.

Opiates are potent analgesics but their clinical use is limited by side effects including analgesic tolerance and opioid-induced hyperalgesia (OIH). The Opiates produce analgesia and other adverse effects through activation of the mu opioid receptor (MOR) encoded by the Oprm1 gene. However, MOR and morphine metabolism involvement in OIH have been little explored. Hence, we examined MOR contribution to OIH by comparing morphine-induced hyperalgesia in wild type (WT) and MOR knockout (KO) mice. We found that repeated morphine administration led to analgesic tolerance and hyperalgesia in WT mice but not in MOR KO mice. The absence of OIH in MOR KO mice was found in both sexes, in two KO global mutant lines, and for mechanical, heat and cold pain modalities. In addition, the morphine metabolite morphine-3beta-D-glucuronide (M3G) elicited hyperalgesia in WT but not in MOR KO animals, as well as in both MOR flox and MOR-Nav1.8 sensory neuron conditional KO mice. M3G displayed significant binding to MOR and G-protein activation when using membranes from MOR-transfected cells or WT mice but not from MOR KO mice. Collectively our results show that MOR is involved in hyperalgesia induced by chronic morphine and its metabolite M3G.

Maternal Use of Opioids During Pregnancy and Congenital Malformations: A Systematic Review.

CONTEXT: Opioid use and abuse have increased dramatically in recent years, particularly among women. OBJECTIVES: We conducted a systematic review to evaluate the association between prenatal opioid use and congenital malformations. DATA SOURCES: We searched Medline and Embase for studies published from 1946 to 2016 and reviewed reference lists to identify additional relevant studies. STUDY SELECTION: We included studies that were full-text journal articles and reported the results of original epidemiologic research on prenatal opioid exposure and congenital malformations. We assessed study eligibility in multiple phases using a standardized, duplicate review process. DATA EXTRACTION: Data on study characteristics, opioid exposure, timing of exposure during pregnancy, congenital malformations (collectively or as individual subtypes), length of follow-up, and main findings were extracted from eligible studies. RESULTS: Of the 68 studies that met our inclusion criteria, 46 had an unexposed comparison group; of those, 30 performed statistical tests to measure associations between maternal opioid use during pregnancy and congenital malformations. Seventeen of these (10 of 12 case-control and 7 of 18 cohort studies) documented statistically significant positive associations. Among the case-control studies, associations with oral clefts and ventricular septal defects/atrial septal defects were the most frequently reported specific malformations. Among the cohort studies, clubfoot was the most frequently reported specific malformation. LIMITATIONS: Variabilities in study design, poor study quality, and weaknesses with outcome and exposure measurement. CONCLUSIONS: Uncertainty remains regarding the teratogenicity of opioids; a careful assessment of risks and benefits is warranted when considering opioid treatment for women of reproductive age.

[Analysis of the accessibility of short acting oral opioids in Hungary]. / A rövid hatású, szájon át adható morfinszármazékok hazai elérhetoségének elemzése.

Short acting oral formulas make part of optimal opioid analgesia. The use of short acting oral morphine has not widely spread in Hungary, and these drugs completely lacked from the market for three years. Since December 2015 short acting morphine-sulphate has again been commercialised. The causes of the market failure are analysed in this article. The aim of the retrospective analysis is to help the accessibility of the medicine to every patient in need. Prescription morphine use depends on the harmonised cooperation of a number of actors. Besides regulating and financing authorities and professional organisations, patients and the opinion forming media are also responsible for building up the right routine.

A review of morphine and morphine-6-glucuronide's pharmacokinetic-pharmacodynamic relationships in experimental and clinical pain.

Morphine is a widely used opioid for treatment of moderate to severe pain, but large interindividual variability in patient response and no clear guidance on how to optimise morphine dosage regimen complicates treatment strategy for clinicians. Population pharmacokinetic-pharmacodynamic models can be used to quantify dose-response relationships for the population as well as interindividual and interoccasion variability. Additionally, relevant covariates for population subgroups that deviate from the typical population can be identified and help clinicians in dose optimisation. This review provides a detailed overview of the published human population pharmacokinetic-pharmacodynamic studies for morphine analgesia in addition to basic drug disposition and pharmacological properties of morphine and its analgesic active metabolite, morphine-6-glucuronide, that may help identify future covariates. Furthermore, based on simulations from key pharmacokinetic-pharmacodynamic models, the contribution of morphine-6-glucuronide to the analgesic response in patients with renal insufficiency was investigated. Simulations were also used to examine the impact of effect-site equilibration half-life on time course of response. Lastly, the impact of study design on the likelihood of determining accurate pharmacodynamic parameters for morphine response was evaluated.

In vivo profiling of seven common opioids for antinociception, constipation and respiratory depression: no two opioids have the same profile.

BACKGROUND AND PURPOSE: For patients experiencing inadequate analgesia and intolerable opioid-related side effects on one strong opioid analgesic, pain relief with acceptable tolerability is often achieved by rotation to a second strong opioid. These observations suggest subtle pharmacodynamic differences between opioids in vivo. This study in rats was designed to assess differences between opioids in their in vivo profiles. EXPERIMENTAL APPROACH: Male Sprague Dawley rats were given single i.c.v. bolus doses of morphine, morphine-6-glucuronide (M6G), fentanyl, oxycodone, buprenorphine, DPDPE ([D-penicillamine(2,5) ]-enkephalin) or U69,593. Antinociception, constipation and respiratory depression were assessed using the warm water tail-flick test, the castor oil-induced diarrhoea test and whole body plethysmography respectively. KEY RESULTS: These opioid agonists produced dose-dependent antinociception, constipation and respiratory depression. For antinociception, morphine, fentanyl and oxycodone were full agonists, buprenorphine and M6G were partial agonists, whereas DPDPE and U69,593 had low potency. For constipation, M6G, fentanyl and buprenorphine were full agonists, oxycodone was a partial agonist, morphine produced a bell-shaped dose-response curve, whereas DPDPE and U69,593 were inactive. For respiratory depression, morphine, M6G, fentanyl and buprenorphine were full agonists, oxycodone was a partial agonist, whereas DPDPE and U69,593 were inactive. The respiratory depressant effects of fentanyl and oxycodone were of short duration, whereas morphine, M6G and buprenorphine evoked prolonged respiratory depression. CONCLUSION AND IMPLICATIONS: For the seven opioids we assessed, no two had the same profile for evoking antinociception, constipation and respiratory depression, suggesting that these effects are differentially regulated. Our findings may explain the clinical success of 'opioid rotation'. LINKED ARTICLES: This article is part of a themed section on Opioids: New Pathways to Functional Selectivity. To view the other articles in this section visit http://dx.doi.org/10.1111/bph.2015.172.issue-2.

A conjugate vaccine attenuates morphine- and heroin-induced behavior in rats.

BACKGROUND: Currently approved medications for opioid addiction have shown clinical efficacy, but undesired side effects, dependence induced by the medications themselves, and low treatment compliance necessitate the need for novel therapies. METHODS: A novel morphine-keyhole limpet hemocyanin conjugate vaccine was synthesized with 6-glutarylmorphine as the hapten and a lengthened linker of 6 carbon atoms. The titer and specificity of the triggered antibody were assessed by enzyme-linked immunosorbent assay. The effects of the vaccine on the morphine-induced elevation of dopamine levels in the nucleus accumbens were determined by high-performance liquid chromatography. The effects of the vaccine on morphine-induced locomotor sensitization and heroin-primed reinstatement of heroin self-administration were also assessed. RESULTS: After subcutaneous administration in rats, the vaccine triggered a high antibody titer, with comparable specificity for morphine, 6-acetylmorphine, and heroin, but no interaction with dissimilar therapeutic opioid compounds, including buprenorphine, naloxone, and nalorphine, was observed. The vaccine significantly prevented the elevation of dopamine levels in the nucleus accumbens induced by a single morphine challenge. Moreover, the vaccine prevented the expression of morphine-induced locomotor sensitization and heroin-primed reinstatement of heroin seeking, suggesting its potential for preventing relapse. CONCLUSION: These results demonstrate that active immunization with the present vaccine induces a robust morphine/heroin-specific antibody response in rats and attenuates the behavioral effects of morphine and heroin.

[Cytokines level in patients with drug-induced jaw necrosis].

The study included 15 patients with purulent inflammatory diseases of maxillofacial area and 25 patients with facial bone necrosis induced by synthetic drugs. Pro- and anti-inflammatory cytokines levels in saliva and wound fluid were analyzed in two groups. The results proved cytokines to play important role in jaw necrosis induced by drugs containing red phosphorus.

A "krokodil" emerges from the murky waters of addiction. Abuse trends of an old drug.

"Krokodil" is the street name for the semi-synthetic opioid derivative desomorphine. Although an old drug, it re-staged on "drug arena" during the last decade causing detrimental effects to its users. Despite the fact that Russia and other former Soviet Republics were the initial plagued countries, "krokodil" arrived in Europe and United States lately, as a substitute of the relative expensive, and in many cases unavailable, heroin. It can be easily manufactured in home-environment from codeine and causes significant health problems, even deaths worldwide. The aim of this review is to summarize the current knowledge about this drug, concerning its chemistry, synthesis, pharmacology and toxicology. Published or reported "krokodil" related cases, fatalities or intoxications, as well as self reports from drug users are reviewed. The existing analytical methodologies for the determination of desomorphine in biological samples as well as its legal status are also presented.

Breaking worse: the emergence of krokodil and excessive injuries among people who inject drugs in Eurasia.

BACKGROUND: Krokodil, a homemade injectable opioid, gained its moniker from the excessive harms associated with its use, such as ulcerations, amputations and discolored scale-like skin. While a relatively new phenomenon, krokodil use is prevalent in Russia and the Ukraine, with at least 100,000 and around 20,000 people respectively estimated to have injected the drug in 2011. In this paper we review the existing information on the production and use of krokodil, within the context of the region's recent social history. METHODS: We searched PubMed, Google Advanced Search, Google Scholar, YouTube and the media search engine www.Mool.com for peer reviewed or media reports, grey literature and video reports. Survey data from HIV prevention and treatment NGOs was consulted, as well as regional experts and NGO representatives. FINDINGS: Krokodil production emerged in an atypical homemade drug production and injecting risk environment that predates the fall of communism. Made from codeine, the active ingredient is reportedly desomorphine, but - given the rudimentary 'laboratory' conditions - the solution injected may include various opioid alkaloids as well as high concentrations of processing chemicals, responsible for the localized and systemic injuries reported here. Links between health care and law enforcement, stigma and maltreatment by medical providers are likely to thwart users seeking timely medical help. CONCLUSION: A comprehensive response to the emergence of krokodil and associated harms should focus both on the substance itself and its rudimentary production methods, as well as on its micro and macro risk environments - that of the on-going syndemic of drug injecting, HIV, HCV, TB and STIs in the region and the recent upheaval in local and international heroin supply. The feasibility of harm reduction strategies for people who inject krokodil may depend more on political will than on the practical implementation of interventions. The legal status of opioid substitution treatment in Russia is a point in case.

Contribution of morphine and morphine-6-glucuronide to respiratory depression in a child.

A morphine plasma concentration/respiratory rate relationship has been described for both adults and children although that of its metabolite, morphine-6-glucuronide, remains uncertain. We describe this relationship in a child with end-stage renal failure who received repeat morphine administration over two days. An EMAX model for additive morphine and morphine-6-glucuronide respiratory effects described respiratory rate better than models describing either alone. Failure to clear morphine-6-glucuronide renally led to respiratory depression episodes occurring later than those predicted by modelling morphine levels only. These findings support the use of alternative analgesics (e.g. fentanyl) that are cleared by non-renal pathways and have no active metabolites in patients with end-stage renal disease.