Pharmacokinetic and neuroimmune pharmacogenetic impacts on slow-release morphine cancer pain control and adverse effects.

The aim was to determine if opioid neuroimmunopharmacology pathway gene polymorphisms alter serum morphine, morphine-3-glucuronide and morphine-6-glucuronide concentration-response relationships in 506 cancer patients receiving controlled-release oral morphine. Morphine-3-glucuronide concentrations (standardised to 11 h post-dose) were higher in patients without pain control (median (interquartile range) 1.2 (0.7-2.3) versus 1.0 (0.5-1.9) µM, P = 0.006), whereas morphine concentrations were higher in patients with cognitive dysfunction (40 (20-81) versus 29 (14-60) nM, P = 0.02). TLR2 rs3804100 variant carriers had reduced odds (adjusted odds ratio (95% confidence interval) 0.42 (0.22-0.82), P = 0.01) of opioid adverse events. IL2 rs2069762 G/G (0.20 (0.06-0.52)), BDNF rs6265 A/A (0.15 (0.02-0.63)) and IL6R rs8192284 carrier (0.55 (0.34-0.90)) genotypes had decreased, and IL6 rs10499563 C/C increased (3.3 (1.2-9.3)), odds of sickness response (P ≤ 0.02). The study has limitations in heterogeneity in doses, sampling times and diagnoses but still suggests that pharmacokinetics and immune genetics co-contribute to morphine pain control and adverse effects in cancer patients.

The pharmacokinetic interaction between nasally administered naloxone and the opioid remifentanil in human volunteers.

PURPOSE: Remifentanil has been shown to increase the bioavailability of nasally administered naloxone. The aim of this study was to explore the nature of this observation. METHODS: We analysed samples from three pharmacokinetic studies to determine the serum concentrations of naloxone-3-glucuronide (N3G), the main metabolite of naloxone, with or without exposure to remifentanil. To enable direct comparison of the three studies, the data are presented as metabolic ratios (ratio of metabolite to mother substance, N3G/naloxone) and dose-corrected values of the area under the curve and maximum concentration (Cmax). RESULTS: Under remifentanil exposure, the time to maximum concentration (Tmax) for N3G was significantly higher for intranasal administration of 71 min compared to intramuscular administration of 40 min. The dose-corrected Cmax of N3G after intranasal administration of naloxone under remifentanil exposure was significantly lower (4.5 ng/mL) than in subjects not exposed to remifentanil (7.8-8.4 ng/mL). The metabolic ratios after intranasal administration rose quickly after 30-90 min and were 2-3 times higher at 360 min compared to intravenous and intramuscular administration. Remifentanil exposure resulted in a much slower increase of the N3G/naloxone ratio after intranasal administration compared to intranasal administration with the absence of remifentanil. After remifentanil infusion was discontinued, this effect gradually diminished. From 240 min there was no significant difference between the ratios observed after intranasal naloxone administration. CONCLUSION: Remifentanil increases the bioavailability of naloxone after nasal administration by reducing the pre-systemic metabolism of the swallowed part of the nasal dose.

Prehospital naloxone administration - what influences choice of dose and route of administration?

BACKGROUND: Amidst the ongoing opioid crisis there are debates regarding the optimal route of administration and dosages of naloxone. This applies both for lay people administration and emergency medical services, and in the development of new naloxone products. We examined the characteristics of naloxone administration, including predictors of dosages and multiple doses during patient treatment by emergency medical service staff in order to enlighten this debate. METHODS: This was a prospective observational study of patients administered naloxone by the Oslo City Center emergency medical service, Norway (2014-2018). Cases were linked to The National Cause of Death Registry. We investigated the route of administration and dosage of naloxone, clinical and demographic variables relating to initial naloxone dose and use of multiple naloxone doses and one-week mortality. RESULTS: Overall, 2215 cases were included, and the majority (91.9%) were administered intramuscular naloxone. Initial doses were 0.4 or 0.8 mg, and 15% of patients received multiple dosages. Unconscious patients or those in respiratory arrest were more likely to be treated with 0.8 mg naloxone and to receive multiple doses. The one-week mortality from drug-related deaths was 4.1 per 1000 episodes, with no deaths due to rebound opioid toxicity. CONCLUSIONS: Intramuscular naloxone doses of 0.4 and 0.8 mg were effective and safe in the treatment of opioid overdose in the prehospital setting. Emergency medical staff appear to titrate naloxone based on clinical presentation.

Ambulance-attended opioid overdoses: An examination into overdose locations and the role of a safe injection facility.

Background: Although the United States and numerous other countries are amidst an opioid overdose crisis, access to safe injection facilities remains limited. Methods: We used prospective data from ambulance journals in Oslo, Norway, to describe the patterns, severity, and outcomes of opioid overdoses and compared these characteristics among various overdose locations. We also examined what role a safe injection facility may have had on these overdoses. Results: Based on 48,825 ambulance calls, 1054 were for opioid overdoses from 465 individuals during 2014 and 2015. The rate of calls for overdoses was 1 out of 48 of the total ambulance calls. Males made up the majority of the sample (n = 368, 79%), and the median age was 35 (range: 18-96). Overdoses occurred in public locations (n = 530, 50.3%), the safe injection facility (n = 353, 33.5%), in private homes (n = 83, 7.9%), and other locations (n = 88, 8.3%). Patients from the safe injection facility and private homes had similarly severe initial clinical symptoms (Glasgow Coma Scale median =3 and respiratory frequency median =4 breaths per minute) when compared with other locations, yet the majority from the safe injection facility did not require further ambulance transport to the hospital (n = 302, 85.6%). Those overdosed in public locations (odds ratio [OR] = 1.66, 95% confidence interval [CI] = 1.17-2.35), and when the safe injection facility was closed (OR =1.4, 95% CI =1.04-1.89), were more likely to receive transport for further treatment. Conclusions: Our findings suggest that the opening hours at the safe injection facility and the overdose location may impact the likelihood of ambulance transport for further treatment.

Naloxone nasal spray - bioavailability and absorption pattern in a phase 1 study. / Naloksonnesespray ­ biotilgjengelighet og opptaksmønster i en fase 1-studie.

BACKGROUND: Bystander administration with naloxone nasal spray can prevent deaths from opioid overdose. To achieve optimal nasal absorption of naloxone, the spray must be administered at low volume with high concentration of the drug. The study aimed to investigate the bioavailability and absorption pattern for a new naloxone nasal spray. MATERIAL AND METHOD: In an open, randomised, two-way crossover study undertaken in five healthy men, naloxone 2 mg (20 mg/ml) in nasal spray was compared with 1 mg intravenously administered naloxone. A total of 15 blood samples were taken over a period of six hours after administration. The drug concentration was determined using liquid chromatography tandem-mass spectrometry. Pharmacokinetic variables were calculated using non-compartmental analysis. RESULTS: Bioavailability for intranasal naloxone was 47 % (minimum-maximum values 24-66 %). Maximum concentration (Cmax) was 4.2 (1.5-7.1) ng/ml, and this was achieved (Tmax ) after 16 (5-25) minutes. INTERPRETATION: The nasal spray resulted in a rapid systemic absorption with higher serum concentrations than intravenous naloxone 10-240 minutes after intake. The pilot study indicated that the highly concentrated nasal spray may provide a therapeutic dose of naloxone with a single spray actuation. The findings led to further commercial development of the medication.

Pharmacodynamics and arteriovenous difference of intravenous naloxone in healthy volunteers exposed to remifentanil.

PURPOSE: Pharmacodynamic studies of naloxone require opioid agonism. Steady state condition may be achieved by remifentanil TCI (target controlled infusion). Opioid agonism can be measured by pupillometry. It is not known whether there are arteriovenous concentration differences for naloxone. The aim was thus to further develop a model for studying pharmacokinetic/pharmacodynamic aspects of naloxone and to explore whether a significant arteriovenous concentration difference for naloxone in humans was present. METHODS: Relevant authorities approved this study. Healthy volunteers (n = 12) were given 1.0 mg intravenous (IV) naloxone after steady state opioid agonism was obtained by TCI of remifentanil (1.3 ng/ml). Opioid effect was measured by pupillometry. Arterial and venous samples were collected simultaneously before and for 2 h after naloxone administration for quantification of naloxone and remifentanil. RESULTS: Arterial remifentanil was in steady state at 12 min. One milligram IV naloxone reversed the effect of remifentanil to 93% of pre-opioid pupil-size within 4 min. The estimated duration of antagonism was 118 min. At that time, the concentration of naloxone was 0.51 ng/ml. The time course of arterial and venous serum concentrations for naloxone was similar, although arterial AUC (area under the curve) was slightly lower (94%) than the venous AUC (p = 0.03). There were no serious adverse events. CONCLUSION: Onset of reversal by IV naloxone was rapid and lasted 118 min. The minimum effective concentration was 0.5 ng/ml. Using TCI remifentanil to obtain a steady-state opioid agonism may be a useful tool to compare new naloxone products.

Pharmacokinetics and -dynamics of intramuscular and intranasal naloxone: an explorative study in healthy volunteers.

PURPOSE: This study aimed to develop a model for pharmacodynamic and pharmacokinetic studies of naloxone antagonism under steady-state opioid agonism and to compare a high-concentration/low-volume intranasal naloxone formulation 8 mg/ml to intramuscular 0.8 mg. METHODS: Two-way crossover in 12 healthy volunteers receiving naloxone while receiving remifentanil by a target-controlled infusion for 102 min. The group were subdivided into three different doses of remifentanil. Blood samples for serum naloxone concentrations, pupillometry and heat pain threshold were measured. RESULTS: The relative bioavailability of intranasal to intramuscular naloxone was 0.75. Pupillometry showed difference in antagonism; the effect was significant in the data set as a whole (p < 0.001) and in all three subgroups (p < 0.02-p < 0.001). Heat pain threshold showed no statistical difference. CONCLUSIONS: A target-controlled infusion of remifentanil provides good conditions for studying the pharmacodynamics of naloxone, and pupillometry was a better modality than heat pain threshold. Intranasal naloxone 0.8 mg is inferior for a similar dose intramuscular. Our design may help to bridge the gap between studies in healthy volunteers and the patient population in need of naloxone for opioid overdose. TRIAL REGISTRATION: clinicaltrials.gov : NCT02307721.

Pharmacokinetics of a new, nasal formulation of naloxone.

PURPOSE: Nasal naloxone is wanted for bystander administration in opioid overdose and as a needle-free alternative for emergency medical personnel. Epidemiologic studies have indicated a therapeutic effect of bystander administration of low-concentration/high-volume formulations. The objective for this study was to describe the nasal pharmacokinetics of a new high-concentration/low-volume nasal formulation of naloxone. METHODS: This was an open, randomized triple crossover trial in healthy, human volunteers (n = 12) where two doses of nasal naloxone (0.8 and 1.6 mg) and one intravenous dose (1.0 mg) were compared. Fifteen serum samples were collected before and until 6 h after naloxone administration. Quantification of naloxone was performed by a validated liquid chromatography-tandem mass spectrometry method. RESULTS: Bioavailability was 0.54 (0.45-0.63) for the 0.8 mg and 0.52 (0.37-0.67) for the 1.6 mg nasal naloxone formulation. Maximum concentration levels (C max) were 1.45 ng/ml (1.07-1.84) for 0.8 mg and 2.57 ng/ml (1.49-3.66) for the 1.6 mg. Time to maximum concentrations (T max) were reached at 17.9 min (11.4-24.5) and 18.6 min (14.4-22.9) for the 0.8 mg and the 1.6 mg doses, respectively. CONCLUSION: This nasal naloxone formulation had a rapid, systemic uptake and higher bioavailability than naloxone formulations not designed for IN use. This indicates that an optimized high-concentration/low-volume nasal spray formulation may deliver a therapeutic dose. The 1.6 mg nasal dose provided serum concentrations that surpassed those of 1.0 mg IV after 15-20 min and stayed above for the rest of the study period.

Prevalence of use of non-prescription analgesics in the Norwegian HUNT3 population: Impact of gender, age, exercise and prescription of opioids.

BACKGROUND: There are concerns about potential increasing use of over-the-counter (OTC) analgesics. The aims of this study were to examine 1) the prevalence of self-reported use of OTC analgesics; 2) the prevalence of combining prescription analgesics drugs with OTC analgesics and 3) whether lifestyle factors such as physical activity were associated with prevalence of daily OTC analgesic use. METHODS: Questionnaire data from the Nord-Trøndelag health study (HUNT3, 2006-08), which includes data from 40,000 adult respondents. The questionnaire included questions on use of OTC analgesics, socioeconomic conditions, health related behaviour, symptoms and diseases. Data were linked to individual data from the Norwegian Prescription Database. A logistic regression was used to investigate the association between different factors and daily use of paracetamol and/or non-steroid anti-inflammatory drugs (NSAIDs) in patients with and without chronic pain. RESULTS: The prevalence of using OTC analgesics at least once per week in the last month was 47%. Prevalence of paracetamol use was almost 40%, compared to 19% and 8% for NSAIDs and acetylsalicylic acid (ASA), respectively. While the use of NSAIDs decreased and the use of ASA increased with age, paracetamol consumption was unaffected by age. Overall more women used OTC analgesics. About 3-5% of subjects using OTC analgesics appeared to combine these with the same analgesic on prescription. Among subjects reporting chronic pain the prevalence of OTC analgesic use was almost twice as high as among subjects without chronic pain. Subjects with little physical activity had 1.5-4 times greater risk of daily use of OTC compared to physically active subjects. CONCLUSIONS: Use of OTC analgesics is prevalent, related to chronic pain, female gender and physical inactivity.

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.

Clinical Pharmacokinetics and Pharmacodynamics of Naloxone.

Naloxone is a World Health Organization (WHO)-listed essential medicine and is the first choice for treating the respiratory depression of opioids, also by lay-people witnessing an opioid overdose. Naloxone acts by competitive displacement of opioid agonists at the µ-opioid receptor (MOR). Its effect depends on pharmacological characteristics of the opioid agonist, such as dissociation rate from the MOR receptor and constitution of the victim. Aim of treatment is a balancing act between restoration of respiration (not consciousness) and avoidance of withdrawal, achieved by titration to response after initial doses of 0.4-2 mg. Naloxone is rapidly eliminated [half-life (t1/2) 60-120 min] due to high clearance. Metabolites are inactive. Major routes for administration are intravenous, intramuscular, and intranasal, the latter primarily for take-home naloxone. Nasal bioavailability is about 50%. Nasal uptake [mean time to maximum concentration (Tmax) 15-30 min] is likely slower than intramuscular, as reversal of respiration lag behind intramuscular naloxone in overdose victims. The intraindividual, interindividual and between-study variability in pharmacokinetics in volunteers are large. Variability in the target population is unknown. The duration of action of 1 mg intravenous (IV) is 2 h, possibly longer by intramuscular and intranasal administration. Initial parenteral doses of 0.4-0.8 mg are usually sufficient to restore breathing after heroin overdose. Fentanyl overdoses likely require higher doses of naloxone. Controlled clinical trials are feasible in opioid overdose but are absent in cohorts with synthetic opioids. Modeling studies provide valuable insight in pharmacotherapy but cannot replace clinical trials. Laypeople should always have access to at least two dose kits for their interim intervention.

Variability in UDP-glucuronosyltransferase genes and morphine metabolism: observations from a cross-sectional multicenter study in advanced cancer patients with pain.

OBJECTIVE: The objective of the present study was to determine whether genetic variability in UDP-glucuronosyltransferase (UGT) genes, together with clinical factors, contribute to variability in morphine glucuronide (M6G and M3G) to morphine serum concentration ratios in patients with advanced cancer receiving chronic morphine therapy. MATERIALS AND METHODS: A total of 41 polymorphisms and predicted haplotypes in the UGT2B7, UGT1A1, and UGT1A8 genes were analyzed in 759 patients who were recruited from the European Pharmacogenetic Opioid Study and received chronic morphine therapy by the oral route (n=635) or parenterally (n=124). The administration groups were analyzed separately by multiple linear regression analyses. RESULTS: Two haplotypes in UGT1A1/UGT1A8 were weak predictors of reduced M6G/morphine and M3G/morphine serum ratios after oral administration (false discovery rate-corrected P-values<0.1). No effect of genotype was seen in the parenteral group. Of the clinical variables (age, sex, BMI, renal function, Karnofsky performance status, and presence of liver metastases), renal function was the major contributor to variation in serum concentration ratios. Concomitant administration of paracetamol predicted significantly higher morphine metabolic ratios after oral administration of morphine (false discovery rate-corrected P-values<2.1E-12). The regression models explained about 35% of the total variability in the data. CONCLUSION: Genetic variation in the UGT genes together with clinical factors influence morphine metabolic ratios in patients with advanced cancer disease and who are scheduled with oral morphine. This information may be included in future research that develop and test new classification systems for opioid treatment in patients with advanced cancer.

Effects of hypothermia on the disposition of morphine, midazolam, fentanyl, and propofol in intensive care unit patients.

Therapeutic hypothermia (TH) may induce pharmacokinetic changes that may affect the level of sedation. We have compared the disposition of morphine, midazolam, fentanyl, and propofol in TH with normothermia in man. Fourteen patients treated with TH following cardiac arrest (33-34°C) were compared with eight matched critically ill patients (36-38°C). Continuous infusions of morphine and midazolam were stopped and replaced with infusions of fentanyl and propofol to describe elimination and start of infusion pharmacokinetics, respectively. Serial serum and urine samples were collected for 6-8 hours for validated quantification and subsequent pharmacokinetic analysis. During TH, morphine elimination half-life (t(1/2)) was significantly higher, while total clearance (CL(tot)) was significantly lower (median [semi-interquartile range (s-iqr)]): t(1/2), 266 (43) versus 168 (11) minutes, P < 0.01; CL(tot), 1201 (283) versus 1687 (200) ml/min, P < 0.01. No significant differences were seen for midazolam. CL(tot) of fentanyl and propofol was significantly lower in hypothermic patients [median (s-iqr)]: fentanyl, 726 (230) versus 1331 (678) ml/min, P < 0.05; propofol, 2046 (305) versus 2665 (223) ml/min, P < 0.05. Compared with the matched, normothermic intensive care unit patients, t(1/2) of morphine was significantly higher during TH. CL(tot) was lower during TH for morphine, fentanyl, and propofol but not for midazolam. Reducing the infusion rates of morphine, fentanyl, and propofol during TH is encouraged.

Use of opioid analgesics in the treatment of cancer pain: evidence-based recommendations from the EAPC.

Here we provide the updated version of the guidelines of the European Association for Palliative Care (EAPC) on the use of opioids for the treatment of cancer pain. The update was undertaken by the European Palliative Care Research Collaborative. Previous EAPC guidelines were reviewed and compared with other currently available guidelines, and consensus recommendations were created by formal international expert panel. The content of the guidelines was defined according to several topics, each of which was assigned to collaborators who developed systematic literature reviews with a common methodology. The recommendations were developed by a writing committee that combined the evidence derived from the systematic reviews with the panellists' evaluations in a co-authored process, and were endorsed by the EAPC Board of Directors. The guidelines are presented as a list of 16 evidence-based recommendations developed according to the Grading of Recommendations Assessment, Development and Evaluation system.

Serum concentrations of opioids when comparing two switching strategies to methadone for cancer pain.

PURPOSE: Our aim was to compare pharmacological aspects of two switching strategies from morphine/oxycodone to methadone; the stop and go (SAG) strategy in which methadone is started directly after the initial opioid has been stopped, and the 3-days switch (3DS), in which morphine/oxycodone is gradually changed to methadone by cross-tapering over 3 days. METHODS: Forty-two cancer patients with pain and/or opioid side effects were assessed in this randomised trial. Trough serum concentrations of methadone, morphine, morphine-6-glucuronide (M6G), and oxycodone were measured on days 1, 2, 3, 4, 7, and 14. Primary outcome was number of patients with methadone concentrations in apparent C(SS) on day 4. Secondary outcomes were exposure to opioids during the first 3 days, interindividual variation of opioid concentrations, and correlation between methadone concentrations and pain intensity (PI) day 3. RESULTS: Thirty-five patients received methadone (16 in the SAG group, 19 in the 3DS group). The median preswitch morphine equivalent doses were 620 (range 350-2000) mg/day in the SAG group and 800 (range 90-3600) mg/day in the 3DS group (p = 0.43);42% reached C(SS) for methadone in the SAG group on day 4 compared with 22% in the 3DS group (p = 0.42). The SAG group was significantly less exposed to morphine/M6G/oxycodone and significantly more exposed to methadone in the first 3 days. Methadone showed a low correlation with PI. More patients dropped out after intervention in the SAG group than in the 3DS group (38% vs. 5%; p = 0.032). One SAG patient suffered from respiratory depression on day 5. CONCLUSION: The SAG group was initially more exposed to methadone and less to the replaced opioids but without observed clinical benefit and with a higher dropout rate. Patients switched to methadone should be followed closely for the first 5 days, regardless of switching strategy.

Do CYP2D6 genotypes reflect oxycodone requirements for cancer patients treated for cancer pain? A cross-sectional multicentre study.

OBJECTIVE: Opioids are recommended by the World Health Organization for moderate to severe cancer pain. Oxycodone is one of the most commonly used opioids and is metabolized in the liver by CYP3A4 and CYP2D6 enzymes. The aim of this cross-sectional study was to assess the relationship between oxycodone pharmacokinetics, pharmacodynamics and the CYP2D6 genotypes "poor metaboliser" (PM), "extensive metaboliser" (EM) and "ultra-rapid metaboliser" (URM) in a cohort of patients with cancer pain. METHODS: The patients were genotyped for the most common CYP2D6 variants and serum concentrations of oxycodone and metabolites were determined. Pain was assessed using the Brief Pain Inventory (BPI). The EORTC QLQ-C30 was used to assess the symptoms of tiredness and nausea. Cognitive function was assessed by the Mini Mental State (MMS) examination. Associations were examined by analyses of variance (ANOVA) and covariance (ANCOVA), or ordinal logistic regressions with and without covariates. RESULTS: The sample consisted of 27 PM, 413 EM (including heterozygotes) and 10 URM. PM had lower oxymorphone and noroxymorphone serum concentrations and oxymorphone to oxycodone ratios than EM and URM. No differences between PM, EM and URM in pain intensity, nausea, tiredness or cognitive function was found. CONCLUSION: CYP2D6 genotypes caused expected differences in pharmacokinetics, but they had no pharmacodynamic consequence. CYP2D6 genotypes did not influence pain control, the adverse symptoms nausea and sedation or the risk for cognitive failure in this study of patients treated with oxycodone for cancer pain.

Does intraoperative ketamine attenuate inflammatory reactivity following surgery? A systematic review and meta-analysis.

BACKGROUND: Reports regarding the ability of the anesthetic drug ketamine to attenuate the inflammatory response to surgery are conflicting. In this systematic review we examined the effect of perioperative ketamine administration on postoperative inflammation as assessed by concentrations of the biomarker interleukin-6 (IL-6). METHODS: This study was based on a systematic search in PubMed, Scopus, Web of Knowledge, and the Cochrane Library. English written randomized controlled trials conducted in humans were eligible. To be included in the analysis, outcome had to relate to inflammation or immune modulation. Each study was reviewed independently by 2 assessors. Data were analyzed according to the GRADE's approach and reported in compliance with the PRISMA recommendations. RESULTS: Fourteen studies were eligible for evaluation (684 patients). Surgery was performed under general anesthesia, and ketamine was given before or during the surgery in varied doses Eight studies involved cardiopulmonary bypass operations, 4 were for abdominal surgery, 1 thoracic surgery, and 1 cataract surgery. Three studies were deemed of low quality. Nine studies measured IL-6 concentrations within the first 6 hours postoperatively; but in 3 studies, other potent anti-inflammatory drugs were used as premedication or during the operation; thus 6 studies (n = 331) were included in the meta-analysis. Using postoperative IL-6 concentrations as an outcome, ketamine had an anti-inflammatory effect; the meta-analysis showed a mean preoperative-postoperative IL-6 concentration difference (95% confidence interval) of -71 (-101 to -41) pg/mL. CONCLUSIONS: It can be concluded that intraoperative administration of ketamine significantly inhibits the early postoperative IL-6 inflammatory response. Future studies should further examine the anti-inflammatory effect of ketamine during major surgery, determine whether ketamine treatment alters functional outcomes, elucidate the mechanisms of its anti-inflammatory effect, and suggest an appropriate dosing regimen.