Oral absorption of oxycodone in patients with short bowel syndrome.

BACKGROUND: Short bowel syndrome is a disorder with several complications such as malnutrition and failure of drug therapy. Treatment with opioids is needed in many patients, and oral medication is preferred. However, optimal dosing is a difficult task as current guidelines are based on an intact gastrointestinal tract. Hence, the aim of this explorative case study was to assess the pharmacokinetics of orally administered oxycodone in patients with short bowel syndrome. METHODS: Six patients with short bowel syndrome were administered 10 mg oral solution oxycodone after an overnight fast. Oxycodone plasma concentrations were determined over a 6-hour period. Pharmacokinetic profiles were visually inspected. Pharmacokinetic parameters: maximum plasma concentration, time of maximum concentration and area under the curve were calculated. Data were also compared to mean values obtained in healthy participants. RESULTS: A clinically relevant concentration of oxycodone was found in all patients, although with large inter-individual variation. The absorption fraction tended to correlate positively with total intestinal length. Additionally, preservation of some or the entire colon seemed further to increase the absorption fraction. Time of maximum concentration varied from 30 min to approximately 90 min. CONCLUSIONS: Oxycodone is absorbed in a clinically relevant extent in patients with short bowel syndrome, but bioavailability varies greatly between patients, which shall be taken into consideration. Absorption is related to functional small intestinal length, but preservation of colon is also beneficial. Still, optimal therapeutic dosing must be individualized, and other factors such as those related to malnutrition and motility shall also be taken into consideration.

Association Between Genetic Polymorphisms and Pain Sensitivity in Patients with Hip Osteoarthritis.

BACKGROUND: Factors such as age, gender, and genetic polymorphisms may explain individual differences in pain phenotype. Genetic associations with pain sensitivity have previously been investigated in osteoarthritis patients, with a focus on the P2X7, TRPV1, and TACR1 genes. However, other genes may play a role as well. Osteoarthritis is a common joint disease, and many patients suffering from this disease are thought to have increased sensitivity to noxious stimuli resulting from sensitization in the nociceptive system. The aim of this study was to investigate if genetic variants of mu, kappa, and delta opioid receptor genes (OPRM1, OPRK1, and OPRD1) and the catechol-O-methyltransferase gene (COMT) influenced the pain phenotype in patients with osteoarthritis. METHODS: The frequencies of 17 polymorphisms were examined. Pain sensitivity was assessed preoperatively by (1) hip rotation, (2) contact heat stimulation, (3) conditioned pain modulation effect, and (4) pressure stimulation at the tibia in both the affected and the unaffected leg. RESULTS: Ninety-two patients (mean age 66 years) with unilateral hip osteoarthritis were included in the study. Carriage of the OPRM1 rs589046T allele was found to be associated with increased pain ratings during hip rotation (P = 0.04) and increased conditioned pain modulation (P = 0.049). Carriage of the OPRD1 rs2234918C allele was found to be associated with an increased pain detection threshold to contact heat stimulation (P = 0.001). No other associations were found (all P > 0.05). CONCLUSION: Results from the present study suggest that, in patients with hip osteoarthritis, genetic variants in OPRM1 and OPRD1 may contribute to the pain phenotype.

Analysis of opioid consumption in clinical trials: a simulation based analysis of power of four approaches.

Inconsistent trial design and analysis is a key reason that few advances in postoperative pain management have been made from clinical trials analyzing opioid consumption data. This study aimed to compare four different approaches to analyze opioid consumption data. A repeated time-to-event (RTTE) model in NONMEM was used to simulate clinical trials of morphine consumption with and without a hypothetical adjuvant analgesic in doses equivalent to 15-62% reduction in morphine consumption. Trials were simulated with duration of 24-96 h. Monte Carlo simulation and re-estimation were performed to determine sample size required to demonstrate efficacy with 80% power using t test, Mann-Whitney rank sum test, time-to-event (TTE) modeling and RTTE modeling. Precision of efficacy estimates for RTTE models were evaluated in 500 simulations. A sample size of 50 patients was required to detect 37% morphine sparing effect with at least 80% power in a 24 h trial with RTTE modeling whereas the required sample size was 200 for Mann-Whitney, 180 for t-test and 76 for TTE models. Extending the trial duration from 24 to 96 h reduced the required sample size by 3.1 fold with RTTE modeling. Precise estimate of potency was obtained with a RTTE model accounting for both morphine effects and time-varying covariates on opioid consumption. An RTTE analysis approach proved better suited for demonstrating efficacy of opioid sparing analgesics than traditional statistical tests as a lower sample size was required due the ability to account for time-varying factors including PK.

A Pharmacokinetic-Pharmacodynamic Model of Morphine Exposure and Subsequent Morphine Consumption in Postoperative Pain.

PURPOSE: To characterize the pharmacokinetic-pharmacodynamic (PK-PD) relationship between exposure of morphine and subsequent morphine consumption and to develop simulation tools for model validation. METHODS: Dose, formulation and time of morphine administration was available from a published study in 63 patients receiving intravenous, oral immediate release or oral controlled release morphine on request after hip surgery. The PK-PD relationship between predicted exposure of morphine and morphine consumption was modeled using repeated time to event (RTTE) modeling in NONMEM. To validate the RTTE model, a visual predictive check method was developed with simulated morphine consumption given the exposure of preceding morphine administration. RESULTS: The probability of requesting morphine was found to be significantly related to the exposure of morphine as well as night/day. Oral controlled release morphine was more effective than intravenous and oral immediate release formulations at equivalent average concentrations. Maximum effect was obtained for 8 h by oral controlled release doses ≥ 15 mg, where probability of requesting a new dose was reduced to 20% for a typical patient. CONCLUSION: This study demonstrates the first quantitative link between exposure of morphine and subsequent morphine consumption and introduces an efficient visual predictive check approach with simulation of adaptive dosing.

Short-term oxycodone treatment does not affect electrogenic ion transport in isolated mucosa from the human rectosigmoid colon.

OBJECTIVE: Opioid therapy is associated with altered secretion and motility of the gut. The relative contribution of decreased secretion to the development of opioid-induced constipation remains unknown. MATERIALS AND METHODS: Twenty-five healthy males were treated with oxycodone for 5 d in a placebo-controlled, randomised cross-over design. Gastrointestinal adverse effects were assessed with validated questionnaires (bowel function index and gastrointestinal symptom rating scale). Rectosigmoid mucosal biopsies were taken at baseline and on day 5 during both treatments and mounted in Ussing chambers. Electrogenic ion transport parameters (short circuit current (SCC) and slope conductance) were measured after addition of secretagogues (prostaglandin E2 (PGE2) (6 µm), theophylline (400 µm)), and an inhibitor (ouabain (200 µm)). Additionally, morphine (50 µm) was added to investigate the direct opioid effect on colonic mucosa. RESULTS: Questionnaires showed pronounced bowel symptoms, including constipation during oxycodone treatment (eight-fold increase in bowel function index score from day 1 to day 5 (p < 0.001) while no significant change occurred during placebo treatment (p = 0.47). Basal SCC and slope conductance did not differ between treatments (all p > 0.05) and application with PGE2, theophylline, and ouabain yielded comparable results on all examinations (all p > 0.05). Morphine application consistently did not evoke a change in ion transport. CONCLUSION: Compared to placebo, epithelial electrogenic ion transport is not altered in mucosal biopsies from the rectosigmoid colon following 5-d oxycodone treatment. The secretory mechanisms in isolated mucosa appear to play a negligible role in the development of opioid-induced constipation.

Repeated Time-to-event Analysis of Consecutive Analgesic Events in Postoperative Pain.

BACKGROUND: Reduction in consumption of opioid rescue medication is often used as an endpoint when investigating analgesic efficacy of drugs by adjunct treatment, but appropriate methods are needed to analyze analgesic consumption in time. Repeated time-to-event (RTTE) modeling is proposed as a way to describe analgesic consumption by analyzing the timing of consecutive analgesic events. METHODS: Retrospective data were obtained from 63 patients receiving standard analgesic treatment including morphine on request after surgery following hip fracture. Times of analgesic events up to 96 h after surgery were extracted from hospital medical records. Parametric RTTE analysis was performed with exponential, Weibull, or Gompertz distribution of analgesic events using NONMEM, version 7.2 (ICON Development Solutions, USA). The potential influences of night versus day, sex, and age were investigated on the probability. RESULTS: A Gompertz distribution RTTE model described the data well. The probability of having one or more analgesic events within 24 h was 80% for the first event, 55% for the second event, 31% for the third event, and 18% for fourth or more events for a typical woman of age 80 yr. The probability of analgesic events decreased in time, was reduced to 50% after 3.3 days after surgery, and was significantly lower (32%) during night compared with day. CONCLUSIONS: RTTE modeling described analgesic consumption data well and could account for time-dependent changes in probability of analgesic events. Thus, RTTE modeling of analgesic events is proposed as a valuable tool when investigating new approaches to pain management such as opioid-sparing analgesia.

Disruption of cortical connectivity during remifentanil administration is associated with cognitive impairment but not with analgesia.

BACKGROUND: The authors investigated the effect of remifentanil administration on resting electroencephalography functional connectivity and its relationship to cognitive function and analgesia in healthy volunteers. METHODS: Twenty-one healthy male adult subjects were enrolled in this placebo-controlled double-blind cross-over study. For each subject, 2.5 min of multichannel electroencephalography recording, a cognitive test of sustained attention (continuous reaction time), and experimental pain scores to bone-pressure and heat stimuli were collected before and after infusion of remifentanil or placebo. A coherence matrix was calculated from the electroencephalogram, and three graph-theoretical measures (characteristic path-length, mean clustering coefficient, and relative small-worldness) were extracted to characterize the overall cortical network properties. RESULTS: Compared to placebo, most graph-theoretical measures were significantly altered by remifentanil at the alpha and low beta range (8 to 18 Hz; all P < 0.001). Taken together, these alterations were characterized by an increase in the characteristic path-length (alpha 17% and low beta range 24%) and corresponding decrements in mean clustering coefficient (low beta range -25%) and relative small-worldness (alpha -17% and low beta range -42%). Changes in characteristic path-lengths after remifentanil infusion were correlated to the continuous reaction time index (r = -0.57; P = 0.009), while no significant correlations between graph-theoretical measures and experimental pain tests were seen. CONCLUSIONS: Remifentanil disrupts the functional connectivity network properties of the electroencephalogram. The findings give new insight into how opioids interfere with the normal brain functions and have the potential to be biomarkers for the sedative effects of opioids in different clinical settings.

Exploratory survey study of long-term users of nicotine replacement therapy in Danish consumers.

BACKGROUND: Long-term use of nicotine replacement therapy (NRT) has been approved in several countries for smokers who are unable or unwilling to quit smoking. However, information on basic characteristics, degree of nicotine dependence, health status and contentment with long-term use of NRT is scarce. The aim of this study was to collect information on the characteristics of long-term NRT users, having used NRT for at least 12 months, reasons for, and contentment with, their continued use of NRT including reasons for wishing to quit or sustain use and an estimation of their degree of nicotine dependence. METHOD: Through advertisements in three national Danish newspapers, long-term NRT users were recruited to answer a short questionnaire about basic characteristics, health status and satisfaction with using NRT. A modified version of the Heaviness of Smoking Index (HSI) questionnaire was applied to estimate nicotine dependence. Linear regression was used to test association between time to first NRT and daily dosage of NRT. RESULTS: A total of 92 respondents were included in the data analysis. A majority of 88% wished to quit NRT for the following reasons: costs of NRT, being tired of feeling addicted and fear of adverse health effects. Scoring on the modified HSI scale was 22.0% low, 68.0% moderate and 9.3% high dependent. Of the respondents, 67.0% used NRT within the first 30 min after waking. A validation check found a significant linear association between the two items in the modified HSI. CONCLUSION: A significant majority of users wished to quit NRT because of the cost of products, being tired of feeling addicted and fear of adverse health consequences. The majority of these users were moderate to high nicotine dependent. The strong association found between time to first NRT and NRT dosages used per day gives reason to believe the validity of the modified HSI. Further studies are required for confirmation. Better counselling of long-term users on the benefits of using NRT compared to smoking should be provided, for those who are chronically dependent, as well as support to stop long-term use of NRT if wanted.

Association Between Human Pain-Related Genotypes and Variability in Opioid Analgesia: An Updated Review.

On an individual level, there is a difference in the analgesic response to a given opioid. Various factors such as gender, age, and genetic variation can affect the analgesic response. The genetic variation can influence pharmacokinetics (eg drug transporters and drug-metabolizing enzymes) and/or pharmacodynamics (eg opioid receptor and catechol-O-methyltransferase enzymes). We present recent experimentally induced pain, postoperative pain, and cancer pain and chronic non-malignant pain conditions studies in humans, focusing on the association between genetic variation and analgesic response assessed as opioid consumption or changes in pain scores. Studies have shown promising results regarding pharmacogenetics as a diagnostic tool for predicting the individual response to a given opioid in the experimental settings; however, in the clinic, it is a more complicated task to accomplish.

Genetic, pathological and physiological determinants of transdermal fentanyl pharmacokinetics in 620 cancer patients of the EPOS study.

OBJECTIVE: This study aimed to investigate whether CYP3A4/5 genetic variants, together with clinical and patient factors, influence serum fentanyl and norfentanyl concentrations and their ratio in cancer pain patients receiving transdermal fentanyl. METHODS: CYP3A4*22 and CYP3A5*3 polymorphisms were analysed in 620 cancer pain patients receiving transdermal fentanyl (12.5-700 µg/h) from the European Pharmacogenetic Opioid Study. Using stepwise linear regression, CYP3A4/5 genetic variability was examined in combination with patient factors relating to organ drug elimination function and ABCB1 genetics for their association with serum fentanyl and norfentanyl concentrations and metabolic ratio (MR) (norfentanyl : fentanyl). RESULTS: Delivery rate-adjusted serum fentanyl concentrations (0.0012-1.1 nmol/l/µg.h) and MRs (0.08-499) varied widely. Only 43% of variability in serum fentanyl concentrations was accounted for by delivery rate and less than 50% by CYP3A4/5 genotypes and clinical variables (delivery rate, sex, comedications, kidney disease, BMI, serum albumin). CYP3A4*22 and CYP3A5*3 variants, CYP3A inhibitors and variables relating to liver and kidney function (serum albumin, glomerular filtration rate, kidney disease, BMI) were associated with MR, but accounted for only 14% of variability. CONCLUSION: Serum fentanyl concentrations and MR vary considerably between cancer pain patients on transdermal fentanyl patches. CYP3A4*22 and CYP3A5*3 genotypes, and multiple clinical factors, combine to influence transdermal fentanyl pharmacokinetics, but accounted for only a small proportion of variability in this study. Identification of the remaining factors determining serum fentanyl concentrations, and their relationship to efficacy and adverse effects may aid in improving the safety and effectiveness of transdermal fentanyl.

Quality of life and symptoms in patients with malignant diseases admitted to a comprehensive cancer centre.

PURPOSE: Quality of life and symptomatology in patients with malignancies admitted to comprehensive cancer centres are rarely investigated. Thus, this study aimed to investigate symptomatology and health-related quality of life of inpatients with cancer. METHODS: A prospective, cross-sectional study was carried out on two occasions 5 weeks apart in haematology and oncology departments at a comprehensive cancer centre. Assessment included demographic data, WHO performance status (PS), EORTC QLQ-C30 and pain scales of brief pain inventory. Comparisons were analysed using Wilcoxon two-sample test, rank tests and Fisher's exact test. RESULTS: One hundred twenty-four patients were analysed, mean age=59 years (SD=13.7), 42% admitted to haematological department; lung cancer was the most frequent diagnosis (15%). Low health-related quality of life and severe symptom burden, especially fatigue and appetite loss, were observed among the inpatients. In addition, role and social functions appeared to be more impaired in haematology patients than in those admitted to oncology (P=0.0372 and 0.0167, respectively). On the other hand, pain and constipation were more severely affected in oncology patients (P=0.0194 and 0.0064, respectively). CONCLUSIONS: Patients in the wards of haematology and oncology had pronounced symptomatology and low quality of life. A more systematic focus on the amelioration of problems with functioning and symptoms among inpatients with malignant diseases is warranted.

Barriers to cancer pain management in Danish and Lithuanian patients treated in pain and palliative care units.

The prevalence of cancer-related pain is high despite available guidelines for the effective assessment and management of that pain. Barriers to the use of opioid analgesics partially cause undertreatment of cancer pain. The aim of this study was to compare pain management outcomes and patient-related barriers to cancer pain management in patient samples from Denmark and Lithuania. Thirty-three Danish and 30 Lithuanian patients responded to, respectively, Danish and Lithuanian versions of the Brief Pain Inventory pain scale, the Barriers Questionnaire II, the Hospital Anxiety and Depression Scale, the Specific Questionnaire On Pain Communication, and the Medication Adherence Report Scale. Emotional distress and patient attitudes toward opioid analgesics in cancer patient samples from both countries explained pain management outcomes in the multivariate regression models. Pain relief and pain medication adherence were better in Denmark, and the country of origin significantly explained the difference in the regression models for these outcomes. In conclusion, interventions in emotional distress and patient attitudes toward opioid analgesics may result in better pain management outcomes generally, whereas poor adherence to pain medication and poor pain relief appear to be more country-specific problems.

Use of drugs with pharmacogenomics (PGx)-based dosing guidelines in a Danish cohort of persons with chronic kidney disease, both on dialysis and not on dialysis: Perspectives for prescribing optimization.

AIM: The objective of this registry study is to assess the utilization of pharmacogenomic (PGx) drugs among patients with chronic kidney disease (CKD). METHODS: This study was a retrospective study of patients affiliated with the Department of Nephrology, Aalborg University Hospital, Denmark in 2021. Patients diagnosed with CKD were divided into CKD without dialysis and CKD with dialysis. PGx prescription drugs were retrieved from the Patient Administration System. Actionable dosing guidelines (AG) for specific drug-gene pairs for CYP2D6, CYP2C9, CYP2C19 and SLCO1B1 were retrieved from the PharmGKB homepage. RESULTS: Out of 1241 individuals, 25.5% were on dialysis. The median number of medications for each patient was 9 within the non-dialysis group and 16 within the dialysis group. Thirty-one distinct PGx drugs were prescribed. Altogether, 76.0% (943 individuals) were prescribed at least one PGx drug and the prevalence of prescriptions of PGx drugs was higher in the dialysis group compared to the non-dialysis group. The most frequently prescribed drugs with AG were metoprolol, pantoprazole, atorvastatin, simvastatin and warfarin. CONCLUSION: This study demonstrated that a substantial proportion of patients with CKD are exposed to drugs or drug combinations for which there exists AG related to PGx of CYP2D6, CYP2C19, CYP2C9 and SLCO1B1.

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.

The Sixth European Society of Pharmacogenomics and Personalised Therapy Congress.

On 8-9 November 2022, the European Society of Pharmacogenomics and Personalised Therapy organized its sixth biennial congress, in Belgrade, Serbia (congress website: www.sspt.rs). The congress aimed to address the current status and future perspectives of pharmacogenomics, share latest knowledge in the field of precision medicine and showcase the implementation of clinical applications in pharmacogenomics/pharmacogenetics. The 2 day congress consisted of 17 lectures given by key-opinion leaders and included a poster session plus discussions. The meeting was a great success by generating an informal environment and enabling the exchange of information between 162 participants from 16 different countries.

A physiologically-based recirculatory meta-model for nasal fentanyl in man.

Pharmacokinetic (PK) and pharmacodynamic (PD) data were available from a study of a nasal delivery system for the opioid analgesic fentanyl, together with data on the kinetics of fentanyl in arterial blood in man, and in the lung and brain of sheep. Our aim was to reconcile these data using a physiologically-based population recirculatory PK-PD model, with emphasis on achieving a meta-model that could simultaneously account for the arterial and venous (arm) concentrations of fentanyl, could relate PD effects (pain scores) to the CNS concentrations of fentanyl, and could account for the effect of body size and age on fentanyl kinetics. Data on the concentration gradients of fentanyl across brain, lung and muscle were used to develop sub-models of fentanyl kinetics in these organs. The sub-models were incorporated into a "whole body" recirculatory model by adding additional sub-models for a venous mixing compartment, the liver and gut, the kidney and the "rest of the body" with blood flows and organ volumes based on values for a Standard Man. Inter-individual variability was achieved by allometric scaling of organ size and blood flows, evidence-based assumptions about the effect of weight and age on cardiac output, and inter-individual variability in the free fraction in plasma and hepatic extraction of fentanyl. Post-operative pain scores were found to be temporally related to the predicted brain concentrations of fentanyl. We conclude that a physiologically-based meta-modelling approach was able to describe clinical PK-PD studies of fentanyl whilst providing a mechanistic interpretation of key aspects of its disposition.

Effect of Roux-en-Y gastric bypass on the pharmacokinetic-pharmacodynamic relationships of liquid and controlled-release formulations of oxycodone.

The physiological changes following Roux-en-Y gastric bypass (RYGB) surgery may impact drug release from mechanistically different controlled-release tablets, making generic substitution inappropriate. This study aimed to characterise the pharmacokinetic-pharmacodynamic relationships of oxycodone from a lipid-based and water-swellable controlled-release tablet in RYGB patients. Twenty RYGB patients received 10-mg oral solution oxycodone or 20-mg controlled-release (water-swellable or lipid-based) oxycodone in a three-way, randomised, semiblinded and cross-over study. Blood sampling and pupillary recordings were conducted over a 24-h period. A previously established pharmacokinetic-pharmacodynamic model of these three formulations in healthy volunteers was used in the analysis as a reference model. No differences in absorption kinetics were seen between controlled-release formulations in patients. However, the absorption lag time was 11.5 min in patients vs 14 min in healthy volunteers for controlled-release tablets (P < 0.001). Furthermore, oral bioavailability was 14.4% higher in patients compared to healthy volunteers regardless of formulation type (P < 0.001). Oxycodone pharmacodynamics were not significantly affected by formulation or patient status. However, baseline pupil diameter was inversely correlated with age (P < 0.001) and plasma concentrations of oxycodone at half-maximum effect were 31% lower in males compared to females (P < 0.05). Generic substitution of monophasic lipid-based and water-swellable controlled-release oxycodone tablets may be considered safe in RYGB patients.

Psychological and behavioural predictors of pain management outcomes in patients with cancer.

To better understand the phenomenon of patient-related barriers to cancer pain management and address them more effectively in interventional studies, a theoretical model related to psychological aspects of pain experience and pain-related behaviours was elaborated. The aim of the study was to analyse the impact of patient-related barriers on cancer pain management outcomes following this model. Thirty-three patients responded to the Brief Pain Inventory Pain scale, the Danish Barriers Questionnaire II (DBQ-II), the Hospital Anxiety and Depression scale (HADS), the Danish version of Patient Perceived Involvement in Care Scale measuring the quality of patient-physician pain communication, and the Danish version of Medication Adherence Report Scale (DMARS-4). Statistical analysis was performed with SPSS 16.00. The results of the multivariable linear regression analyses showed that pain intensity was explained by patients' emotional distress (symptoms of anxiety and depression) and that pain relief was explained by cognitive barriers. In conclusion, interventions in emotional distress and patients' concerns may supposedly result in better cancer pain management outcomes.

[Opioids for chronic non-malignant pain].

In recent years, the use of opioids in Denmark has been under scrutiny due to various government measures to reduce consumption, greater media focus and Denmark's relatively larger consumption of opioids compared with the Nordic neighbours. Consequently, opioid prescriptions in Denmark have declined since 2017. A more nuanced approach to opioid treatment for non-malignant chronic pain, which includes individualised treatment as well as enhanced interdisciplinary collaboration, is required as argued in this review.

Chronic abdominal pain and persistent opioid use after bariatric surgery.

Background and aims Bariatric surgery remains a mainstay for treatment of morbid obesity. However, long-term adverse outcomes include chronic abdominal pain and persistent opioid use. The aim of this review was to assess the existing data on prevalence, possible mechanisms, risk factors, and outcomes regarding chronic abdominal pain and persistent opioid use after bariatric surgery. Methods PubMed was screened for relevant literature focusing on chronic abdominal pain, persistent opioid use and pharmacokinetic alterations of opioids after bariatric surgery. Relevant papers were cross-referenced to identify publications possibly not located during the ordinary screening. Results Evidence regarding general chronic pain status after bariatric surgery is sparse. However, our literature review revealed that abdominal pain was the most prevalent complication to bariatric surgery, presented in 3-61% of subjects with health care contacts or readmissions 1-5 years after surgery. This could be explained by behavioral, anatomical, and/or functional disorders. Persistent opioid use and doses increased after bariatric surgery, and 4-14% initiated a persistent opioid use 1-7 years after the surgery. Persistent opioid use was associated with severe pain symptoms and was most prevalent among subjects with a lower socioeconomic status. Alteration of absorption and distribution after bariatric surgery may impact opioid effects and increase the risk of adverse events and development of addiction. Changes in absorption have been briefly investigated, but the identified alterations could not be separated from alterations caused solely by excessive weight loss, and medication formulation could influence the findings. Subjects with persistent opioid use after bariatric surgery achieved lower weight loss and less metabolic benefits from the surgery. Thus, remission from comorbidities and cost effectiveness following bariatric surgery may be limited in these subjects. Conclusions Pain, especially chronic abdominal, and persistent opioid use were found to be prevalent after bariatric surgery. Physiological, anatomical, and pharmacokinetic changes are likely to play a role. However, the risk factors for occurrence of chronic abdominal pain and persistent opioid use have only been scarcely examined as have the possible impact of pain and persistent opioid use on clinical outcomes, and health-care costs. This makes it difficult to design targeted preventive interventions, which can identify subjects at risk and prevent persistent opioid use after bariatric surgery. Future studies could imply pharmacokinetic-, pharmacodynamics-, and physiological-based modelling of pain treatment. More attention to social, physiologic, and psychological factors may be warranted in order to identify specific risk profiles of subjects considered for bariatric surgery in order to tailor and optimize current treatment recommendations for this population.