The pharmacokinetics of morphine and morphine glucuronides in kidney failure

Anaesthesia in chronic dialysis patients: A narrative review

The provision of anaesthesia for individuals receiving chronic dialysis can be challenging. Sedation and anaesthesia are frequently managed by critical care clinicians in the intensive care unit or operating room. This narrative review summarizes the important principles of sedation and anaesthesia for individuals on long-term dialysis, with reference to the best available evidence. Topics covered include the pharmacology of anaesthetic agents, the impacts of patient characteristics upon the pre-anaesthetic assessment and critical illness, and the fundamentals of dialysis access procedures.

Morphine and hydromorphone pharmacokinetics in human volunteers: population-based modelling of interindividual and opioid-related variability

BACKGROUND

Morphine and hydromorphone have differing onsets, magnitudes, and durations of effects and side-effects. Differences between opioids in their interindividual variabilities in pharmacokinetics and pharmacodynamics might influence rational drug selection. Crossover drug studies can provide more informative interindividual variability data than parallel group studies. Using data from a crossover study of i.v. morphine and hydromorphone in healthy volunteers, we tested the hypothesis that morphine and hydromorphone differ in their interindividual pharmacokinetic variability.

METHODS

Arterial opioid and metabolite concentrations from a randomised crossover study in 51 volunteers receiving a 2-h infusion of hydromorphone (0.05 or 0.1 mg kg-1 i.v.) or morphine (total 0.1 or 0.2 mg kg-1 i.v.) 1-2 weeks apart were evaluated with a three-compartmental model for parent opioid and incorporating glucuronides using population modelling (NONMEM). The primary outcome was interindividual variability in pharmacokinetics, based on the coefficient of variation (%CV) of individual model parameters, calculated as √[exp(ω2)-1]×100 where ω2 is the interindividual variability.

RESULTS

Data were analysed per drug and in a combined morphine-hydromorphone model. Both analyses indicate that interindividual variabilities for hydromorphone and morphine were comparable with %CV ranging from 9% to 31% for structural model parameters (combined analysis). Similarly, additive and relative residual errors had comparable variabilities, 20-40% and 72-87%, respectively, for morphine and hydromorphone (combined analysis).

CONCLUSIONS

Morphine and hydromorphone did not differ in a statistically significant or clinically meaningful manner in their interindividual pharmacokinetic variability. Interindividual pharmacokinetic variability does not appear a meaningful consideration in the choice between these two opioids.

Consensus document on palliative care in cardiorenal patients

There is an unmet need to create consensus documents on the management of cardiorenal patients since, due to the aging of the population and the rise of both pathologies, these patients are becoming more prevalent in daily clinical practice. Chronic kidney disease coexists in up to 40%-50% of patients with chronic heart failure cases. There have yet to be consensus documents on how to approach palliative care in cardiorenal patients. There are guidelines for patients with heart failure and chronic kidney disease separately, but they do not specifically address patients with concomitant heart failure and kidney disease. For this reason, our document includes experts from different specialties, who will not only address the justification of palliative care in cardiorenal patients but also how to identify this patient profile, the shared planning of their care, as well as knowledge of their trajectory and the palliative patient management both in the drugs that will help us control symptoms and in advanced measures. Dialysis and its different types will also be addressed, as palliative measures and when the decision to continue or not perform them could be considered. Finally, the psychosocial approach and adapted pharmacotherapy will be discussed.

Role of the Microbiome in Gut-Heart-Kidney Cross Talk

Homeostasis is a prerequisite for health. When homeostasis becomes disrupted, dysfunction occurs. This is especially the case for the gut microbiota, which under normal conditions lives in symbiosis with the host. As there are as many microbial cells in and on our body as human cells, it is unlikely they would not contribute to health or disease. The gut bacterial metabolism generates numerous beneficial metabolites but also uremic toxins and their precursors, which are transported into the circulation. Barrier function in the intestine, the heart, and the kidneys regulates metabolite transport and concentration and plays a role in inter-organ and inter-organism communication via small molecules. This communication is analyzed from the perspective of the remote sensing and signaling theory, which emphasizes the role of a large network of multispecific, oligospecific, and monospecific transporters and enzymes in regulating small-molecule homeostasis. The theory provides a systems biology framework for understanding organ cross talk and microbe-host communication involving metabolites, signaling molecules, nutrients, antioxidants, and uremic toxins. This remote small-molecule communication is critical for maintenance of homeostasis along the gut-heart-kidney axis and for responding to homeostatic perturbations. Chronic kidney disease is characterized by gut dysbiosis and accumulation of toxic metabolites. This slowly impacts the body, affecting the cardiovascular system and contributing to the progression of kidney dysfunction, which in its turn influences the gut microbiota. Preserving gut homeostasis and barrier functions or restoring gut dysbiosis and dysfunction could be a minimally invasive way to improve patient outcomes and quality of life in many diseases, including cardiovascular and kidney disease.

EtG Quantification in Hair and Different Reference Cut-Offs in Relation to Various Pathologies: A Scoping Review

Ethyl glucuronide (EtG) is a non-volatile, non-oxidative, hydrophilic, and stable ethanol phase II metabolite. EtG is produced through ethanol glucuronidation by UDP-glucuronosyltransferase (UGT), a phase II enzyme. EtG can be extracted from different biological matrices, including keratin ones, such as hair or nails. The purpose of this scoping review is to describe the relationship between EtG levels in hair and some of the most common and frequent pathological conditions and verify whether different reference cut-offs in relation to various pathologies have been identified in the scientific literature. In fact, in-depth knowledge of the influence of pathologies, such as diabetes mellitus, hepatic and renal dysfunction, on EtG production and its storage in keratin matrices would allow a more appropriate interpretation of obtained data and rule out false positives or false negatives. This scoping review is based on bibliographic research carried out on PubMed regarding the quantification of EtG in hair of subjects affected by different pathological conditions. According to the scientific literature, the main and most common pathologies that can affect the concentration of EtG in hair are liver and kidney diseases and diabetes. The EtG quantification analytical data should be interpreted carefully as they may have a great impact in both forensic and clinical contexts.

Opioids and Vitamin C: Known Interactions and Potential for Redox-Signaling Crosstalk

Opioids are among the most widely used classes of pharmacologically active compounds both clinically and recreationally. Beyond their analgesic efficacy via μ opioid receptor (MOR) agonism, a prominent side effect is central respiratory depression, leading to systemic hypoxia and free radical generation. Vitamin C (ascorbic acid; AA) is an essential antioxidant vitamin and is involved in the recycling of redox cofactors associated with inflammation. While AA has been shown to reduce some of the negative side effects of opioids, the underlying mechanisms have not been explored. The present review seeks to provide a signaling framework under which MOR activation and AA may interact. AA can directly quench reactive oxygen and nitrogen species induced by opioids, yet this activity alone does not sufficiently describe observations. Downstream of MOR activation, confounding effects from AA with STAT3, HIF1α, and NF-κB have the potential to block production of antioxidant proteins such as nitric oxide synthase and superoxide dismutase. Further mechanistic research is necessary to understand the underlying signaling crosstalk of MOR activation and AA in the amelioration of the negative, potentially fatal side effects of opioids.

Opioids for chronic pain management in patients with dialysis-dependent kidney failure

Chronic pain is highly prevalent among adults treated with maintenance haemodialysis (HD) and has profound negative effects. Over four decades, research has demonstrated that 50-80% of adult patients treated with HD report having pain. Half of patients with HD-dependent kidney failure (HDKF) have chronic moderate-to-severe pain, which is similar to the burden of pain in patients with cancer. However, pain management in patients with HDKF is often ineffective as most patients report that their pain is inadequately treated. Opioid analgesics are prescribed more frequently for patients receiving HD than for individuals in the general population with chronic pain, and are associated with increased morbidity, mortality and health-care resource use. Furthermore, current opioid prescribing patterns are frequently inconsistent with guideline-recommended care. Evidence for the effectiveness of opioids in pain management in general, and in patients with HDKF specifically, is lacking. Nonetheless, long-term opioid therapy has a role in the treatment of some patients when used selectively, carefully and combined with an ongoing assessment of risks and benefits. Here, we provide a comprehensive overview of the use of opioid therapy in patients with HDKF and chronic pain, including a discussion of buprenorphine, which has potential as an analgesic option for patients receiving HD owing to its unique pharmacological properties.

Bridging the gap between in silico and in vivo by modeling opioid disposition in a kidney proximal tubule microphysiological system

Opioid overdose, dependence, and addiction are a major public health crisis. Patients with chronic kidney disease (CKD) are at high risk of opioid overdose, therefore novel methods that provide accurate prediction of renal clearance (CL_r) and systemic disposition of opioids in CKD patients can facilitate the optimization of therapeutic regimens. The present study aimed to predict renal clearance and systemic disposition of morphine and its active metabolite morphine-6-glucuronide (M6G) in CKD patients using a vascularized human proximal tubule microphysiological system (VPT-MPS) coupled with a parent-metabolite full body physiologically-based pharmacokinetic (PBPK) model. The VPT-MPS, populated with a human umbilical vein endothelial cell (HUVEC) channel and an adjacent human primary proximal tubular epithelial cells (PTEC) channel, successfully demonstrated secretory transport of morphine and M6G from the HUVEC channel into the PTEC channel. The in vitro data generated by VPT-MPS were incorporated into a mechanistic kidney model and parent-metabolite full body PBPK model to predict CL_r and systemic disposition of morphine and M6G, resulting in successful prediction of CL_r and the plasma concentration–time profiles in both healthy subjects and CKD patients. A microphysiological system together with mathematical modeling successfully predicted renal clearance and systemic disposition of opioids in CKD patients and healthy subjects.

Narcotic Use for Acute Postoperative Pain Management in Mohs Micrographic Surgery Patients With End Stage Renal Disease: A Review of the Literature

BACKGROUND

Uncontrolled acute postoperative pain presents a significant management challenge when opioids are used in patients with end-stage renal disease (ESRD). Currently, there is a lack of quality pharmacokinetic and pharmacodynamic data regarding opioid medication use in ESRD patients to optimize safe and effective management.

OBJECTIVE

To review the published literature on pharmacologic evidence for and against the use of opioid medications for acute postoperative pain following Mohs micrographic surgery in ESRD patients.

METHODS

A search of PubMed was conducted to identify articles on the pharmacokinetic and pharmacodynamic properties of opioid pain medications in ESRD patients through March 1, 2020.

RESULTS

Seventy-five articles were reviewed. Limited data exist on opioids safe for use in ESRD and are mostly confined to small case series. Studies suggest tramadol and hydromorphone could be considered when indicated. Methadone may be a safe option, but should be reserved for treatment coordinated by a trained pain subspecialist.

CONCLUSION

Randomized clinical trials are lacking. Studies that are available are not sufficient to perform a quantitative methodologic approach. Evidence supports the judicious use of postoperative opioid medications in ESRD patients at the lowest possible dose to achieve clinically meaningful improvement in pain and function.

Anesthetic Considerations in Alström Syndrome: A Case Report

Alström syndrome is a rare genetic condition that affects cardiac, respiratory, endocrine, hepatorenal, gastrointestinal, auditory, ophthalmic, and musculoskeletal systems. This multisystem syndrome poses significant anesthetic challenges, along with a high likelihood of perioperative adverse clinical outcomes. A literature review revealed no reports on the anesthetic management for emergency surgery in adults with Alström syndrome. We report the perioperative management of a patient with Alström syndrome who presented for an emergency laparotomy due to an ischemic bowel. This report highlights perioperative challenges in the management of this condition in the emergency setting.

Clinical pharmacology and dosing regimen optimization of neonatal opioid withdrawal syndrome treatments

In this paper, we review the management of neonatal opioid withdrawal syndrome (NOWS) and clinical pharmacology of primary treatment agents in NOWS, including morphine, methadone, buprenorphine, clonidine, and phenobarbital. Pharmacologic treatment strategies in NOWS have been mostly empirical, and heterogeneity in dosing regimens adds to the difficulty of extrapolating study results to broader patient populations. As population pharmacokinetics (PKs) of pharmacologic agents in NOWS become more well‐defined and knowledge of patient‐specific factors affecting treatment outcomes continue to accumulate, PK/pharmacodynamic modeling and simulation will be powerful tools to aid the design of optimal dosing regimens at the patient level. Although there is an increasing number of clinical trials on the comparative efficacy of treatment agents in NOWS, here, we also draw attention to the importance of optimizing the dosing regimen, which can be arguably equally important at identifying the optimal treatment agent.

Pharmacokinetics of Morphine and Morphine-6-Glucuronide During Postoperative Pain Therapy in Cardiac Surgery Patients

BACKGROUND AND OBJECTIVE

Morphine is a standard analgesic drug for postoperative pain therapy. This study aimed to evaluate the pharmacokinetics of morphine and its active metabolite morphine-6-glucuronide (M6G) in cardiac surgery  patients during postoperative analgesia.

METHODS

Twenty-five adult patients undergoing cardiac surgery received postoperative pain therapy by patient-controlled analgesia with intravenous bolus doses of morphine. Plasma concentrations of morphine and M6G were determined from arterial samples. Population pharmacokinetic parameters were estimated using nonlinear mixed-effects modeling.

RESULTS

Data from twenty-one patients (aged 44-79 years) were analyzed. Pharmacokinetics were best described by a three-compartment model for morphine and a two-compartment model for M6G, linked by a transit compartment. Mean (±SD) population estimates for morphine were: clearance (CL) = 1.35±0.40 L/min, central volume of distribution (V₁) = 8.1±2.2 L, steady-state volume of distribution (V_ss) = 207±83 L, terminal elimination half-life (T_1/2γ) = 177±50 min. Clearance of morphine was proportional to cardiac output. Mean (±SD) population estimates for M6G were: CL = 0.098±0.037 L/min, V₁ = 5.5±0.8 L, V_ss = 15.8±0.8 L, T_1/2β = 227±74 min. The time to peak concentration of M6G after a bolus dose of morphine was 53±20 min. Clearance of M6G was proportional to estimated glomerular filtration rate.

CONCLUSIONS

The pharmacokinetics of morphine and M6G in pain therapy of cardiac surgery  patients could be well described by standard compartmental models. Cardiac output was identified as a significant covariate for morphine clearance, whereas renal function was identified as the most significant covariate for clearance of M6G. These effects should be particularly considered if morphine is administered as a continuous infusion. The developed pharmacokinetic model also enables patient-controlled target-controlled infusion for pain therapy with morphine.

TRIAL REGISTRATION

Clinical Trials NCT02483221 (June 26, 2015).

Enzyme Kinetics of Uridine Diphosphate Glucuronosyltransferases (UGTs)

Glucuronidation, catalyzed by uridine diphosphate glucuronosyltransferases (UGTs), is an important process for the metabolism and clearance of many lipophilic chemicals, including drugs, environmental chemicals, and endogenous compounds. Glucuronidation is a bisubstrate reaction that requires the aglycone and the cofactor, UDP-GlcUA. Accumulating evidence suggests that the bisubstrate reaction follows a compulsory-order ternary mechanism. To simplify the kinetic modeling of glucuronidation reactions in vitro, UDP-GlcUA is usually added to incubations in large excess. Many factors have been shown to influence UGT activity and kinetics in vitro, and these must be accounted for during experimental design and data interpretation. While the assessment of drug-drug interactions resulting from UGT inhibition has been challenging in the past, the increasing availability of UGT enzyme-selective substrate and inhibitor "probes" provides the prospect for more reliable reaction phenotyping and assessment of drug-drug interaction potential. Although extrapolation of the in vitro intrinsic clearance of a glucuronidated drug often underpredicts in vivo clearance, careful selection of in vitro experimental conditions and inclusion of extrahepatic glucuronidation may improve the predictivity of in vitro-in vivo extrapolation. Physiologically based pharmacokinetic (PBPK) modeling has also shown to be of value for predicting PK of drugs eliminated by glucuronidation.

Impaired diagnostic accuracy of hair ethyl glucuronide testing in patients with renal dysfunction

The impact of renal impairment and hemodialysis on ethyl glucuronide concentrations in hair (hEtG) is not well known. Here, hEtG levels were determined by liquid chromatography-tandem mass spectrometry (LC-MS/MS) in patients presenting to the transplant outpatient clinic and compared with the self-reported alcohol consumption in an anonymous validated questionnaire. Estimated daily alcohol intake (EDI) was calculated. A total of 94 patients with varying renal function (Glomerular filtration rate (GFR) > 60 mL/min: group 1 (n = 47); GFR 30-60 ml/min: group 2 (n = 29); GFR < 30 mL/min: group 3 (n = 18)) were included in the study. Fifteen of 18 (83.3%) patients in group 3 were on dialysis. Altogether, hEtG tested positive (> 5 pg/mg) in 25.5% (n = 24) of patients, while 36.2% (n = 34) and 14.9% (n = 14) of patients reported any or regular (> 10 g/d) alcohol consumption, respectively. The median hEtG concentration of positive samples was much higher in patients in group 3 with advanced renal dysfunction or on dialysis than in patients in group 1 or 2 (group 1, 2, 3 dialysis patients: 74, 52, 145 and 155 pg/mg, respectively), although they consumed on average much less alcohol per day (median EDI group 1, 2, 3, dialysis patients: 16, 17, 3 and 3 g/d, respectively). Also, there was a significant correlation between the hEtG concentration and EDI for patients in group 1 (ρ = 0.84; p = 0.01), but not for patients in group 2 (ρ = -0.35, p = 0.39) or 3 (ρ = 0.02, p = 0.96). Furthermore, the ability of hEtG to correctly identify abstainers as such was lower for patients with advanced renal dysfunction than for the remaining patients (specificity for group 1, 2, 3: 92%, 87%, 82%, respectively). So, monitoring hEtG concentration was less reliable in patients with advanced renal dysfunction or on hemodialysis and by far overestimated the amount of alcohol consumed.

Pharmacokinetics in children with chronic kidney disease

In children, the main causes of chronic kidney disease (CKD) are congenital diseases and glomerular disorders. CKD is associated with multiple physiological changes and may therefore influence various pharmacokinetic (PK) parameters. A well-known consequence of CKD on pharmacokinetics is a reduction in renal clearance due to a decrease in the glomerular filtration rate. The impact of renal impairment on pharmacokinetics is, however, not limited to a decreased elimination of drugs excreted by the kidney. In fact, renal dysfunction may lead to modifications in absorption, distribution, transport, and metabolism as well. Currently, insufficient evidence is available to guide dosing decisions on many commonly used drugs. Moreover, the impact of maturation on drug disposition and action should be taken into account when selecting and dosing drugs in the pediatric population. Clinicians should take PK changes into consideration when selecting and dosing drugs in pediatric CKD patients in order to avoid toxicity and increase efficiency of drugs in this population. The aim of this review is to summarize known PK changes in relation to CKD and to extrapolate available knowledge to the pediatric CKD population to provide guidance for clinical practice.

Opioid Safety and Concomitant Benzodiazepine Use in End-Stage Renal Disease Patients

Background

Opioid use is common in end-stage renal disease (ESRD) patients. However, safety of individual opioids and concomitant benzodiazepine use has not been studied.

Objective

To study the epidemiology of opioid and concomitant benzodiazepine use in ESRD population. To study the clinical safety profile of individual opioids in patients on hemodialysis.

Design

Retrospective analysis of the U.S. Renal Data System. A comprehensive review of the current literature was performed to update currently used opioid safety classification.

Participants

ESRD patients ≥18 years on hemodialysis who were enrolled in Medicare A and B and Part D between 2006 and 2012, excluding those with malignancy.

Main Measures

Hospital admission with diagnosis of prescription opioid overdose within 30, 60, and 90 days of prescription; death due to opioid overdose.

Results

Annually, the percentage of patients prescribed any opioid was 52.2%. Overall trend has been increasing except for a small dip in 2011, despite which the admissions due to opioid overdose have been rising. 30% of those who got a prescription for opioids also got a benzodiazepine prescription. 56.5% of these patients received both prescriptions within a week of each other. Benzodiazepine use increased the odds of being on opioids by 3.27 (CI 3.21–3.32) and increased the odds of hospitalization by 50%. Opioids considered safe such as fentanyl and methadone were associated with 3 and 6 folds higher odds of hospitalization within 30 days of prescription. Hydrocodone had the lowest odds ratio (1.9, CI 1.8–2.0).

Conclusions

Concurrent benzodiazepine use is common and associated with higher risk of hospitalization due to opioid overdose. Possible opioid-associated hospital admission rate is 4-5 times bigger in ESRD population than general population. Current safety classification of opioids in these patients is misleading, and even drugs considered safe based on pharmacokinetic data are associated with moderate to very high risk of hospitalization. We propose a risk-stratified classification of opioids and suggest starting to use them in all ESRD patients.

Safe Opioid Use: Management of Opioid-Related Adverse Effects and Aberrant Behaviors

Opioids are highly effective for cancer pain but are associated with multiple adverse effects and risk of addiction. This article provides a synopsis on the management of various opioid-related adverse effects and strategies to minimize aberrant opioid use in patients who have cancer. Many adverse effects can be effectively managed. Some patients on chronic opioid therapy may demonstrate aberrant behaviors suggestive of opioid misuse or diversion. Through intensive education, longitudinal monitoring, early identification, and timely management, clinicians can optimize the risk to benefit ratio to support safe opioid use.

Update of the Scientific Opinion on opium alkaloids in poppy seeds

Poppy seeds are obtained from the opium poppy (Papaver somniferum L.). They are used as food and to produce edible oil. The opium poppy plant contains narcotic alkaloids such as morphine and codeine. Poppy seeds do not contain the opium alkaloids, but can become contaminated with alkaloids as a result of pest damage and during harvesting. The European Commission asked EFSA to provide an update of the Scientific Opinion on opium alkaloids in poppy seeds. The assessment is based on data on morphine, codeine, thebaine, oripavine, noscapine and papaverine in poppy seed samples. The CONTAM Panel confirms the acute reference dose (ARfD) of 10 μg morphine/kg body weight (bw) and concluded that the concentration of codeine in the poppy seed samples should be taken into account by converting codeine to morphine equivalents, using a factor of 0.2. The ARfD is therefore a group ARfD for morphine and codeine, expressed in morphine equivalents. Mean and high levels of dietary exposure to morphine equivalents from poppy seeds considered to have high levels of opium alkaloids (i.e. poppy seeds from varieties primarily grown for pharmaceutical use) exceed the ARfD in most age groups. For poppy seeds considered to have relatively low concentrations of opium alkaloids (i.e. primarily varieties for food use), some exceedance of the ARfD is also seen at high levels of dietary exposure in most surveys. For noscapine and papaverine, the available data do not allow making a hazard characterisation. However, comparison of the dietary exposure to the recommended therapeutical doses does not suggest a health concern for these alkaloids. For thebaine and oripavine, no risk characterisation was done due to insufficient data. However, for thebaine, limited evidence indicates a higher acute lethality than for morphine and the estimated exposure could present a health risk.

Pain Therapy Guided by Purpose and Perspective in Light of the Opioid Epidemic

Prescription opioid misuse is an ongoing and escalating epidemic. Although these pharmacological agents are highly effective analgesics prescribed for different types of pain, opioids also induce euphoria, leading to increasing diversion and misuse. Opioid use and related mortalities have developed in spite of initial claims that OxyContin, one of the first opioids prescribed in the USA, was not addictive in the presence of pain. These claims allayed the fears of clinicians and contributed to an increase in the number of prescriptions, quantity of drugs manufactured, and the unforeseen diversion of these drugs for non-medical uses. Understanding the history of opioid drug development, the widespread marketing campaign for opioids, the immense financial incentive behind the treatment of pain, and vulnerable socioeconomic and physical demographics for opioid misuse give perspective on the current epidemic as an American-born problem that has expanded to global significance. In light of the current worldwide opioid epidemic, it is imperative that novel opioids are developed to treat pain without inducing the euphoria that fosters physical dependence and addiction. We describe insights from preclinical findings on the properties of opioid drugs that offer insights into improving abuse-deterrent formulations. One finding is that the ability of some agonists to activate one pathway over another, or agonist bias, can predict whether several novel opioid compounds bear promise in treating pain without causing reward among other off-target effects. In addition, we outline how the pharmacokinetic profile of each opioid contributes to their potential for misuse and discuss the emergence of mixed agonists as a promising pipeline of opioid-based analgesics. These insights from preclinical findings can be used to more effectively identify opioids that treat pain without causing physical dependence and subsequent opioid abuse.

Bioanalytical methods for the quantification of hydromorphone, fentanyl, norfentanyl, morphine, morphine-3ß-glucuronide and morphine-6ß-glucuronide in human plasma

The aim of this study was to develop an assay for the quantification of hydromorphone, morphine, fentanyl and the metabolites norfentanyl, morphine-3ß-glucuronide and morphine-6ß-glucuronide in human plasma to support pharmacokinetic studies investigating the large interpatient variability in response to opioid treatment. For the quantitation of hydromorphone, morphine, fentanyl and its metabolite norfentanyl aliquots of 200μL human potassium EDTA plasma were deproteinized with deuterated internal standards in a mixture of acetonitrile and acetone, followed by a liquid-liquid extraction with 4% ammonium hydroxide and ethyl acetate. Morphine-3ß-glucuronide and morphine-6ß-glucuronide were extracted by a solid phase extraction using 10mM ammonium carbonate pH 8.8 and a deuterated internal standards solution. Morphine, hydromorphone, fentanyl and norfentanyl were separated on an Aquity UPLC^® BEH C18 column 1.7μm, 100mm×2.1mm at 50°C. Separation, was achieved on a gradient of methanol with an overall run time of 6min. The compounds were quantified by triple-quadrupole mass spectrometry in the positive ion electrospray ionization mode. Morphine-3ß-glucuronide and morphine-6ß-glucuronide were separated on a VisionHT C18-P; 3μm 2.1×50mm, column at 40°C on a gradient of acetonitrile, with an overall run time of 10min. Both methods were precise and accurate, with within-run and between-run precisions within acceptable limits and accuracy ranging from 84.0 to 105.5%. The methods were successfully applied to support clinical pharmacological studies in patients treated with opioids for the treatment of moderate to severe cancer-related pain.

Pharmacokinetics of Morphine, Morphine-3-Glucuronide and Morphine-6-Glucuronide in Terminally Ill Adult Patients

Background and Objective

Morphine dosing can be challenging in terminally ill adult patients due to the heterogeneous nature of the population and the difficulty of accurately assessing pain during sedation. To determine the pharmacokinetics of morphine, morphine-3-glucuronide (M3G) and morphine-6-glucuronide (M6G) in this population, and to find clinically relevant parameters for dose individualisation, we performed a population pharmacokinetic analysis.

Methods

Blood samples were randomly collected from 47 terminally ill patients in both the pre-terminal and terminal phases. Nonlinear mixed-effects modelling (NONMEM) was used to develop a population pharmacokinetic model and perform covariate analysis.

Results

The data were accurately described by a two-compartment model for morphine with two one-compartment models for both its metabolites. Typical morphine clearance was 48 L/h and fell exponentially by more than 10 L/h in the last week before death. Decreased albumin levels and a decreased estimated glomerular filtration rate (eGFR) resulted in lower metabolite clearance. Between-subject variability in clearance was 52 % (morphine), 75 % (M3G) and 79 % (M6G), and changed to 53, 29 and 34 %, respectively, after inclusion of the covariates.

Conclusions

Our results show that morphine clearance decreased up to the time of death, falling by more than 10 L/h (26 %) in the last week before death, and that M3G and M6G accumulated due to decreased renal function. Further studies are warranted to determine whether dose adjustment of morphine is required in terminally ill patients.

Emergency medicine evaluation and management of the end stage renal disease patient

BACKGROUND

End stage renal disease (ESRD) is increasing in the U.S., and these patients demonstrate greater all-cause mortality, cardiovascular events, and hospitalization rates when compared to those with normal renal function. These patients may experience significant complications associated with loss of renal function and dialysis.

OBJECTIVE

This review evaluates complications of ESRD including cardiopulmonary, neurologic, infectious disease, vascular, and access site complications, as well as medication use in this population.

DISCUSSION

ESRD incidence is rapidly increasing, and patients commonly require renal replacement therapy including hemodialysis (HDS) or peritoneal dialysis (PD), each type with specific features. These patients possess greater risk of neurologic complications, cardiopulmonary pathology, infection, and access site complications. Focused history and physical examination are essential. Neurologic issues include uremic encephalopathy, cerebrovascular pathology, and several others. Cardiopulmonary complications include pericarditis, pericardial effusion/tamponade, acute coronary syndrome, sudden cardiac death, electrolyte abnormalities, pulmonary edema, and air embolism. Infections are common, with patients more commonly presenting in atypical fashion. Access site infections and metastatic infections must be treated aggressively. Access site complications include bleeding, aneurysm/pseudoaneurysm, thrombosis/stenosis, and arterial steal syndrome. Specific medication considerations are required for analgesics, sedatives, neuromuscular blocking agents, antimicrobials, and anticoagulants.

CONCLUSIONS

Consideration of renal physiology with complications in ESRD can assist emergency providers in the evaluation and management of these patients. ESRD affects many organ systems, and specific pharmacologic considerations are required.

The Role of the Kidney in Drug Elimination: Transport, Metabolism, and the Impact of Kidney Disease on Drug Clearance

Recent advances in the identification and characterization of renal drug transporters and drug-metabolizing enzymes has led to greater understanding of their roles in drug and chemical elimination and in modulation of the intrarenal exposure and response to drugs, nephrotoxic compounds, and physiological mediators. Furthermore, there is increasing awareness of the potential importance of drug-drug interactions (DDIs) arising from inhibition of renal transporters, and regulatory agencies now provide recommendations for the evaluation of transporter-mediated DDIs. Apart from the well-recognized effects of kidney disease on renal drug clearance, there is a growing body of evidence demonstrating that the nonrenal clearances of drugs eliminated by certain transporters and drug-metabolizing enzymes are decreased in patients with chronic kidney disease (CKD). Based on these observations, renal impairment guidance documents of regulatory agencies recommend pharmacokinetic characterization of both renally cleared and nonrenally cleared drugs in CKD patients to inform possible dosage adjustment.

Glucuronidation: driving factors and their impact on glucuronide disposition

Glucuronidation is a well-recognized phase II metabolic pathway for a variety of chemicals including drugs and endogenous substances. Although it is usually the secondary metabolic pathway for a compound preceded by phase I hydroxylation, glucuronidation alone could serve as the dominant metabolic pathway for many compounds, including some with high aqueous solubility. Glucuronidation involves the metabolism of parent compound by UDP-glucuronosyltransferases (UGTs) into hydrophilic and negatively charged glucuronides that cannot exit the cell without the aid of efflux transporters. Therefore, elimination of parent compound via glucuronidation in a metabolic active cell is controlled by two driving forces: the formation of glucuronides by UGT enzymes and the (polarized) excretion of these glucuronides by efflux transporters located on the cell surfaces in various drug disposition organs. Contrary to the common assumption that the glucuronides reaching the systemic circulation were destined for urinary excretion, recent evidences suggest that hepatocytes are capable of highly efficient biliary clearance of the gut-generated glucuronides. Furthermore, the biliary- and enteric-eliminated glucuronides participate into recycling schemes involving intestinal microbes, which often prolong their local and systemic exposure, albeit at low systemic concentrations. Taken together, these recent research advances indicate that although UGT determines the rate and extent of glucuronide generation, the efflux and uptake transporters determine the distribution of these glucuronides into blood and then to various organs for elimination. Recycling schemes impact the apparent plasma half-life of parent compounds and their glucuronides that reach intestinal lumen, in addition to prolonging their gut and colon exposure.

Management of Chronic Kidney Disease Patients in the Intensive Care Unit: Mixing Acute and Chronic Illness

Patients with chronic kidney disease (CKD) are at high risk for developing critical illness and for admission to intensive care units (ICU). 'Critically ill CKD patients' frequently develop an acute worsening of renal function (i.e. acute-on-chronic, AoC) that contributes to long-term kidney dysfunction, potentially leading to end-stage kidney disease (ESKD). An integrated multidisciplinary effort is thus necessary to adequately manage the multi-organ damage of those kidney patients and contemporaneously reduce the progression of kidney dysfunction when they are critically ill. The aim of this review is to describe (1) the pathophysiological mechanisms underlying the development of AoC kidney dysfunction and its role in the progression toward ESKD; (2) the most common clinical presentations of critical illness among CKD/ESKD patients; and (3) the continuum of care for CKD/ESKD patients from maintenance hemodialysis/peritoneal dialysis to acute renal replacement therapy performed in ICU and, vice-versa, for AoC patients who develop ESKD.

Pharmacokinetic considerations and recommendations in palliative care, with focus on morphine, midazolam and haloperidol

INTRODUCTION

A variety of medications are used for symptom control in palliative care, such as morphine, midazolam and haloperidol. The pharmacokinetics of these drugs may be altered in these patients as a result of physiological changes that occur at the end stage of life.

AREAS COVERED

This review gives an overview of how the pharmacokinetics in terminally ill patients may differ from the average population and discusses the effect of terminal illness on each of the four pharmacokinetic processes absorption, distribution, metabolism, and elimination. Specific considerations are also given for three commonly prescribed drugs in palliative care: morphine, midazolam and haloperidol).

EXPERT OPINION

The pharmacokinetics of drugs in terminally ill patients can be complex and limited evidence exists on guided drug use in this population. To improve the quality of life of these patients, more knowledge and more pharmacokinetic/pharmacodynamics studies in terminally ill patients are needed to develop individualised dosing guidelines. Until then knowledge of pharmacokinetics and the physiological changes that occur in the final days of life can provide a base for dosing adjustments that will improve the quality of life of terminally ill patients. As the interaction of drugs with the physiology of dying is complex, pharmacological treatment is probably best assessed in a multi-disciplinary setting and the advice of a pharmacist, or clinical pharmacologist, is highly recommended.

A Synopsis of Clinical Pharmacokinetic Alterations in Advanced CKD

Unrecognized alterations in pharmacokinetics, which quantitatively describes the time course of drug disposition in the body, may lead to clinically significant changes in systemic exposure and corresponding response to drugs in patients with chronic kidney disease (CKD). Clinicians must take pharmacokinetic changes into consideration when selecting and dosing medications in CKD patients to optimize the risk:benefit ratio. Pharmacokinetic changes in absorption, distribution, and renal clearance are well characterized and generally predictable for most drugs. Conversely, changes in nonrenal clearance are less well understood and corresponding clinical implications are still being elucidated. This review provides a synopsis of alterations in each of these pharmacokinetic parameters observed in patients with advanced CKD.

Consequences of renal failure on non-renal clearance of drugs

Kidney disease not only alters the renal elimination but also the non-renal disposition of drugs that are metabolized by the liver. Indeed, modifications in the expression and activity of intestinal and hepatic drug metabolism enzymes and uptake and efflux transporters have been reported. Accumulated uremic toxins, inflammatory cytokines, and parathyroid hormones may modulate these proteins either directly or by inhibiting gene expression. This can lead to important unintended variations in exposure and response when drugs are administered without dose adjustment for reduced renal function. This review summarizes our current understanding of non-renal clearance in circumstances of chronic and acute renal failure with experimental but also clinical studies. It also evaluates the clinical impact on drug disposition. Predicting the extent of the drug disposition modification is difficult first because of the complex interplay between metabolic enzymes and transport proteins but also because of the differential effects in the different organs (liver, intestines). Recommendations of the US FDA are presented as they may be potentially helpful tools to predict these modifications when no specific pharmacokinetic studies are available.

Confronting the challenges of effective pain management in children following tonsillectomy

Tonsillectomy is an extremely common surgical procedure associated with significant morbidity and mortality. The post-operative challenges include: respiratory complications, post-tonsillectomy hemorrhage, nausea, vomiting and significant pain. The present model of care demands that most of these children are managed in an ambulatory setting. The recent Federal Drug Agency (FDA) warning contraindicating the use of codeine after tonsillectomy in children represents a significant change of practice for many pediatric otolaryngological surgeons. This introduces a number of other safety concerns when deciding on a safe alternative to codeine, especially since most tonsillectomy patients are managed by lay primary caregiver's at home. This review outlines the safety issues and proposes, based on currently available evidence, a preventative multi-modal strategy to manage pain, nausea and vomiting without increasing the risk of post-tonsillectomy bleeding.

Oral administration of morphine versus ibuprofen to manage postfracture pain in children: a randomized trial

BACKGROUND

Recent warnings from Health Canada regarding codeine for children have led to increased use of nonsteroidal anti-inflammatory drugs and morphine for common injuries such as fractures. Our objective was to determine whether morphine administered orally has superior efficacy to ibuprofen in fracture-related pain.

METHODS

We used a parallel group, randomized, blinded superiority design. Children who presented to the emergency department with an uncomplicated extremity fracture were randomly assigned to receive either morphine (0.5 mg/kg orally) or ibuprofen (10 mg/kg) for 24 hours after discharge. Our primary outcome was the change in pain score using the Faces Pain Scale - Revised (FPS-R). Participants were asked to record pain scores immediately before and 30 minutes after receiving each dose.

RESULTS

We analyzed data from 66 participants in the morphine group and 68 participants in the ibuprofen group. For both morphine and ibuprofen, we found a reduction in pain scores (mean pre-post difference ± standard deviation for dose 1: morphine 1.5 ± 1.2, ibuprofen 1.3 ± 1.0, between-group difference [δ] 0.2 [95% confidence interval (CI) -0.2 to 0.6]; dose 2: morphine 1.3 ± 1.3, ibuprofen 1.3 ± 0.9, δ 0 [95% CI -0.4 to 0.4]; dose 3: morphine 1.3 ± 1.4, ibuprofen 1.4 ± 1.1, δ -0.1 [95% CI -0.7 to 0.4]; and dose 4: morphine 1.5 ± 1.4, ibuprofen 1.1 ± 1.2, δ 0.4 [95% CI -0.2 to 1.1]). We found no significant differences in the change in pain scores between morphine and ibuprofen between groups at any of the 4 time points (p = 0.6). Participants in the morphine group had significantly more adverse effects than those in the ibuprofen group (56.1% v. 30.9%, p < 0.01).

INTERPRETATION

We found no significant difference in analgesic efficacy between orally administered morphine and ibuprofen. However, morphine was associated with a significantly greater number of adverse effects. Our results suggest that ibuprofen remains safe and effective for outpatient pain management in children with uncomplicated fractures.

TRIAL REGISTRATION

ClinicalTrials.gov, no. NCT01690780.

Pharmacokinetic considerations in chronic kidney disease and patients requiring dialysis

INTRODUCTION

Chronic kidney disease (CKD) is the progressive decline in renal function over time. Patients with end-stage renal disease require renal replacement therapy such as hemodialysis to support life. Hemodialysis patients require several medications to treat a variety of comorbid conditions. Polypharmacy accompanied by alterations in the pharmacokinetics of medications places hemodialysis patients at increased risk of drug accumulation and adverse events.

AREAS COVERED

We review alterations in the pharmacokinetics of drugs in hemodialysis patients. The major areas of pharmacokinetics, absorption, distribution, metabolism and excretion, are covered and, where appropriate, differences between dialysis patients and non-dialysis CKD patients are compared. In addition, we review the importance of drug dialyzability and its potential impact on drug efficacy. Finally, we describe important clinical examples demonstrating nonrenal drug clearance is significantly altered in CKD.

EXPERT OPINION

Decreases in renal drug excretion experienced by hemodialysis patients have been known for years. Recent animal and human clinical pharmacokinetic studies have highlighted that nonrenal clearance of drugs is also substantially decreased in CKD. Clinical pharmacokinetic studies are required to determine the optimal dosage of drugs in CKD and hemodialysis patients in order to decrease the incidence of adverse medication events in these patient populations.

Differences between opioids: pharmacological, experimental, clinical and economical perspectives

Clinical studies comparing the response and side effects of various opioids have not been able to show robust differences between drugs. Hence, recommendations of the regulatory authorities have been driven by costs with a general tendency in many countries to restrict physician's use of opioids to morphine. Although this approach is recognized as cost-effective in most cases there is solid evidence that, on an individual patient basis, opioids are not all equal. Therefore it is important to have an armamentarium of strong analgesics in clinical practice to ensure a personalized approach in patients who do not respond to standard treatment. In this review we highlight differences between opioids in human studies from a pharmacological, experimental, clinical and health economics point of view. We provide evidence that individuals respond differently to opioids, and that general differences between classes of opioids exist. We recommend that this recognition is used to individualize treatment in difficult cases allowing physicians to have a wide range of treatment options. In the end this will reduce pain and side effects, leading to improved quality of life for the patient and reduce the exploding pain related costs.