Race, Gender, and Genetic Polymorphism Contribute to Variability in Acetaminophen Pharmacokinetics, Metabolism, and Protein-Adduct Concentrations in Healthy African-American and European-American Volunteers

Identification of ADME genes polymorphic variants linked to trastuzumab-induced cardiotoxicity in breast cancer patients: Case series of mono-institutional experience

BACKGROUND

Long-term survival induced by anticancer treatments discloses emerging frailty among breast cancer (BC) survivors. Trastuzumab-induced cardiotoxicity (TIC) is reported in at least 5% of HER2+BC patients. However, TIC mechanism remains unclear and predictive genetic biomarkers are still lacking. Interaction between systemic inflammation, cytokine release and ADME genes in cancer patients might contribute to explain mechanisms underlying individual susceptibility to TIC and drug response variability. We present a single institution case series to investigate the potential role of genetic variants in ADME genes in HER2+BC patients TIC experienced.

METHODS

We selected data related to 40 HER2+ BC patients undergone to DMET genotyping of ADME constitutive variant profiling, with the aim to prospectively explore their potential role in developing TIC. Only 3 patients ("case series"), who experienced TIC, were compared to 37 "control group" matched patients cardiotoxicity-sparing. All patients underwent to left ventricular ejection fraction (LVEF) evaluation at diagnosis and during anti-HER2 therapy. Each single probe was clustered to detect SNPs related to cardiotoxicity.

RESULTS

In this retrospective analysis, our 3 cases were homogeneous in terms of clinical-pathological characteristics, trastuzumab-based treatment and LVEF decline. We identified 9 polymorphic variants in 8 ADME genes (UGT1A1, UGT1A6, UGT1A7, UGT2B15, SLC22A1, CYP3A5, ABCC4, CYP2D6) potentially associated with TIC.

CONCLUSION

Real-world TIC incidence is higher compared to randomized clinical trials and biomarkers with potential predictive value aren't available. Our preliminary data, as proof of concept, could suggest a predictive role of pharmacogenomic approach in the identification of cardiotoxicity risk biomarkers for anti-HER2 treatment.

Acetaminophen treatment in children and adults with spinal muscular atrophy: a lower tolerance and higher risk of hepatotoxicity

Acute liver failure has been reported sporadically in patients with spinal muscular atrophy (SMA) and other neuromuscular disorders with low skeletal muscle mass receiving recommended dosages of acetaminophen. It is suggested that low skeletal muscle mass may add to the risk of toxicity. We aimed to describe the pharmacokinetics and safety of acetaminophen in patients with SMA. We analyzed acetaminophen metabolites and liver biomarkers in plasma from SMA patients and healthy controls (HC) every hour for six or eight hours on day 1 and day 3 of treatment with therapeutic doses of acetaminophen. Twelve patients with SMA (six adults and six children) and 11 HC participated in the study. Adult patients with SMA had significantly lower clearance of acetaminophen compared to HC (14.1 L/h vs. 21.5 L/h). Formation clearance of acetaminophen metabolites, glucuronide, sulfate, and oxidative metabolites were two-fold lower in the patients compared to HC. The liver transaminases and microRNAs increased nine-fold in one adult SMA patient after two days of treatment. The other patients and HC did not develop abnormal liver biomarkers. In this study, patients with SMA had lower clearance and slower metabolism of acetaminophen, and one patient developed liver involvement. We recommend giving 15 mg/kg/dose to SMA adults (with a maximum of 4000 mg/day) and monitoring standard liver biomarkers 48 h after first-time treatment of acetaminophen.

The impact of race and gender on the outcomes of patients with acetaminophen-induced acute liver failure: propensity score-matched analysis of the NIS database

BACKGROUND

Acetaminophen overdose is one of the leading causes of acute liver failure in the USA. In this study, we investigated the impact of race and gender on the hospital outcomes of patients admitted with acetaminophen-induced acute liver failure.

METHODS

From the National Inpatient Sample between the years 2016 and 2019, patients with acetaminophen-induced acute liver failure were selected and stratified based on gender (Male and Female) and race (White, Black and Hispanic). The cases were propensity score-matched to controls (male and Whites) and were compared along the following endpoints: mortality, length of stay, hospitalization costs, and hepatic complications.

RESULTS

Among patients with acetaminophen-induced acute liver failure, females experienced higher rates of mortality (16.60% vs. 11.70%, P = 0.004) and clinical illness, including hypotension (11.80% vs. 7.15%, P = 0.002) and ventilator use (40.80% vs. 30.00%, P < 0.001). When stratified by race, Black patients had longer hospital stays (Black vs. White, 8.76 days vs. 7.46 days, P = 0.03). There were no significant differences in outcomes between Hispanic and White patients. No significant differences in mortality were shown between races.

CONCLUSION

We found that females had a higher rate of mortality and incidence of hepatic encephalopathy compared to males. When stratified by race, Blacks were shown to have longer hospital stay. Females and racial minorities were also affected by special healthcare needs after discharge compared to their male and White cohorts, respectively.

Pharmacokinetics of single dose administration of three increasing doses of acetaminophen per os in 1-3-month-old foals

BACKGROUND

Acetaminophen is a common analgesic and antipyretic drug used in human medicine and might be an alternative to nonsteroidal anti-inflammatory drugs for treating pain and pyrexia in foals. The pharmacokinetics and safety of differing doses of acetaminophen have not been investigated in foals.

OBJECTIVES

To determine the plasma pharmacokinetics and any changes in haematology and biochemistry profiles following oral administration of single doses of acetaminophen at 10, 20, and 40 mg/kg to foals.

STUDY DESIGN

Randomised cross-over pharmacokinetic study.

METHODS

Six Quarter Horse (two colts and four fillies) foals received 10, 20, and 40 mg/kg acetaminophen orally once. Haematology and biochemistry profiles were performed before and 7 days after each drug administration. Blood samples were collected over 64 h after drug administration and were used to quantify plasma acetaminophen concentrations by liquid chromatography. Pharmacokinetic parameters were determined using compartmental analysis.

RESULTS

Median (range) acetaminophen plasma concentrations were 4.4 (1.8-5.1), 6.3 (2.6-12.6), and 14 (7.3-18) μg/ml for the 10, 20, and 40 mg/kg doses, respectively. Median acetaminophen area under the concentration versus time curve (AUC)0-∞ ranged from 25 (11-32), 41 (22-74), and 105 (82-142) h × μg/ml for the 10, 20, and 40 mg/kg doses, respectively. Dose-normalised maximal concentrations and AUC0-∞ values were similar across dose concentrations (p > 0.05). Median terminal half-life for all doses was 2.7-2.8 h. Haematology and biochemistry profiles were normal except for blood urea nitrogen and alkaline phosphatase concentrations.

MAIN LIMITATIONS

Foals were growing throughout the study, starting at 1 month and ending at 3 months. Deposition of drugs changes with age. The sample size was small and only single doses were evaluated. No liver biopsies were performed.

CONCLUSION

Plasma disposition of acetaminophen after a single oral dose of 10, 20, and 40 mg/kg to 1-3-month-old foals varies greatly with the dose. The analgesic and antipyretic effect in foals is unknown.

Advances in the understanding of acetaminophen toxicity mechanisms: a clinical toxicology perspective

INTRODUCTION

Acetaminophen (paracetamol) is a commonly used analgesic and antipyretic agent, which is safe in therapeutic doses. Acetaminophen poisoning due to self-harm or repeated supratherapeutic ingestion is a common cause of acute liver injury. Acetylcysteine has been a mainstay of treatment for acetaminophen poisoning for decades and is efficacious if administered early. However, treatment failures occur if administered late, in 'massive' overdoses or in high-risk patients.

AREAS COVERED

This review provides an overview of the mechanisms of toxicity of acetaminophen poisoning (metabolic and oxidative phase) and how this relates to the assessment and treatment of the acetaminophen poisoned patient. The review focuses on how these advances offer further insight into the utility of novel biomarkers and the role of proposed adjunct treatments.

EXPERT OPINION

Advances in our understanding of acetaminophen toxicity have allowed the development of novel biomarkers and a better understanding of how adjunct treatments may prevent acetaminophen toxicity. Newly proposed adjunct treatments like fomepizole are being increasingly used without robust clinical trials. Novel biomarkers (not yet clinically available) may provide better assessment of these newly proposed adjunct treatments, particularly in clinical trials. These advances in our understanding of acetaminophen toxicity and liver injury hold promise for improved diagnosis and treatment.

A Multi-Omic Mosaic Model of Acetaminophen Induced Alanine Aminotransferase Elevation

BACKGROUND

Acetaminophen (APAP) is the most common cause liver injury following alcohol in US patients. Predicting liver injury and subsequent hepatic regeneration in patients taking therapeutic doses of APAP may be possible using new 'omic methods such as metabolomics and genomics. Multi'omic techniques increase our ability to find new mechanisms of injury and regeneration.

METHODS

We used metabolomic and genomic data from a randomized controlled trial of patients administered 4 g of APAP per day for 14 days or longer with blood samples obtained at 0 (baseline), 4, 7, 10, 13 and 16 days. We used the highest ALT as the clinical outcome to be predicted in our integrated analysis. We used penalized regression to model the relationship between genetic variants and day 0 metabolite level, and then performed a metabolite-wide colocalization scan to associate the genetically regulated component of metabolite expression with ALT elevation. Genome-wide association study (GWAS) analyses were conducted for ALT elevation and metabolite level using linear regression, with age, sex, and the first five principal components included as covariates. Colocalization was tested via a weighted sum test.

RESULTS

Out of the 164 metabolites modeled, 120 met the criteria for predictive accuracy and were retained for genetic analyses. After genomic examination, eight metabolites were found to be under genetic control and predictive of ALT elevation due to therapeutic acetaminophen. The metabolites were: 3-oxalomalate, allantoate, diphosphate, L-carnitine, L-proline, maltose, and ornithine. These genes are important in the tricarboxylic acid cycle (TCA), urea breakdown pathway, glutathione production, mitochondrial energy production, and maltose metabolism.

CONCLUSIONS

This multi'omic approach can be used to integrate metabolomic and genomic data allowing identification of genes that control downstream metabolites. These findings confirm prior work that have identified mitochondrial energy production as critical to APAP induced liver injury and have confirmed our prior work that demonstrate the importance of the urea cycle in therapeutic APAP liver injury.

Drug Metabolism of Hepatocyte-like Organoids and Their Applicability in In Vitro Toxicity Testing

Emerging advances in the field of in vitro toxicity testing attempt to meet the need for reliable human-based safety assessment in drug development. Intrahepatic cholangiocyte organoids (ICOs) are described as a donor-derived in vitro model for disease modelling and regenerative medicine. Here, we explored the potential of hepatocyte-like ICOs (HL-ICOs) in in vitro toxicity testing by exploring the expression and activity of genes involved in drug metabolism, a key determinant in drug-induced toxicity, and the exposure of HL-ICOs to well-known hepatotoxicants. The current state of drug metabolism in HL-ICOs showed levels comparable to those of PHHs and HepaRGs for CYP3A4; however, other enzymes, such as CYP2B6 and CYP2D6, were expressed at lower levels. Additionally, EC50 values were determined in HL-ICOs for acetaminophen (24.0−26.8 mM), diclofenac (475.5−>500 µM), perhexiline (9.7−>31.5 µM), troglitazone (23.1−90.8 µM), and valproic acid (>10 mM). Exposure to the hepatotoxicants showed EC50s in HL-ICOs comparable to those in PHHs and HepaRGs; however, for acetaminophen exposure, HL-ICOs were less sensitive. Further elucidation of enzyme and transporter activity in drug metabolism in HL-ICOs and exposure to a more extensive compound set are needed to accurately define the potential of HL-ICOs in in vitro toxicity testing.

A study of the regional differences in propacetamol-related adverse events using VigiBase data of the World Health Organization

Upon withdrawal of propacetamol, an injectable formulation of the paracetamol prodrug, in Europe due to safety concerns, South Korea's regulatory body requested a post-marketing surveillance study exploring its safety profile. We characterized regional disparities in adverse events (AE) associated with propacetamol between Asia and Europe using the World Health Organization's pharmacovigilance database, VigiBase. We performed disproportionality analyses using reporting odds ratios (rOR) and information component (IC) to determine whether five AEs (anaphylaxis, Stevens-Johnson syndrome, thrombosis, contact dermatitis/eczema, injection site reaction [ISR]) were associated with propacetamol versus non-propacetamol injectable antipyretics in Asia and Europe, separately. In Asia, there was a high reporting ratio of propacetamol-related ISR (rOR 5.72, 95% CI 5.19-6.31; IC₀₂₅ 1.27), satisfying the signal criteria; there were no reports of thrombosis and contact dermatitis/eczema. Two signals were identified in Europe, with higher reporting ratios for thrombosis (rOR 7.45, 95% CI 5.19-10.71; IC₀₂₅ 1.92) and contact dermatitis/eczema (rOR 16.73, 95% CI 12.48-22.42; IC₀₂₅ 2.85). Reporting ratios of propacetamol-related anaphylaxis were low for Asia and Europe. While signals were found for thrombosis and contact dermatitis/eczema in Europe, these were not detected in Asia. These findings suggest potential ethnic differences in propacetamol-related AEs between Asia and Europe, which could serve as supportive data for future decision-making.

Type 2 diabetes: an exploratory genetic association analysis of selected metabolizing enzymes and transporters and effects on cardiovascular and renal biomarkers

OBJECTIVES

This study sought to identify potential pharmacogenetic associations of selected enzymes and transporters with type 2 diabetes (T2D). In addition, pharmacogenomic profiles, concentrations of asymmetric dimethylarginine (ADMA) or kidney injury molecule-1 (KIM-1), and several covariates were investigated.

METHODS

Whole blood was collected from 63 patients, with 32 individuals with T2D. A pharmacogenomic panel was used to assay genetic profiles, and biomarker ELISAs were run to determine subject concentrations of ADMA and KIM-1. Additive genetic modeling with multiple linear and logistic regressions were performed to discover potential SNPs-outcome associations using PLINK.

RESULTS

Ten SNPs were found to be significant (p<0.05) depending on the inclusion or exclusion of covariates. Of these, four were found in association with the presence of T2D, rs2231142, rs1801280, rs1799929, and rs1801265 depending on covariate inclusion or exclusion. Regarding ADMA, one SNP was found to be significant without covariates, rs1048943. Five SNPs were identified in association with KIM-1 and T2D in the presence of covariates, rs12208357, rs34059508, rs1058930, rs1902023, and rs3745274. Biomarker concentrations were not significantly different in the presence of T2D.

CONCLUSIONS

This exploratory study found several SNPs related to T2D; further research is required to validate and understand these relationships.

Molecular monitoring of patient response to painkiller drugs

INTRODUCTION

Non-steroidal anti-inflammatory drugs and opioids are widely prescribed for the treatment of mild to severe pain. Wide interindividual variability regarding the analgesic efficacy and adverse reactions to these drugs (ADRs) exist, although the mechanisms responsible for these ADRs are not well understood.

AREAS COVERED

We provide an overview of the clinical impact of variants in genes related to the pharmacokinetics and pharmacodynamics of painkillers, as well as those associated with the susceptibility to ADRs. Also, we discuss the current pharmacogenetic-guided treatment recommendations for the therapeutic use of non-steroidal anti-inflammatory drugs and opioids.

EXPERT OPINION

In the light of the data analyzed, common variants in genes involved in pharmacokinetics and pharmacodynamics processes may partially explain the lack of response to painkiller treatment and the occurrence of adverse drug reactions. The implementation of high-throughput sequencing technologies may help to unveil the role of rare variants as considerable contributors to explaining the interindividual variability in drug response. Furthermore, a consensus between the diverse pharmacogenetic guidelines is necessary to extend the implementation of pharmacogenetic-guided prescription in daily clinical practice. Additionally, the physiologically-based pharmacokinetics and pharmacodynamics modeling techniques may contribute to the improvement of these guidelines and facilitate clinicians drug dose adjustment.

Common UGT1A6 Variant Alleles Determine Acetaminophen Pharmacokinetics in Man

Acetaminophen (paracetamol) is a widely used drug that causes adverse drug events that are often dose-dependent and related to plasma drug concentrations. Acetaminophen metabolism strongly depends on UGT1A enzymes. We aimed to investigate putative factors influencing acetaminophen pharmacokinetics. We analyzed acetaminophen pharmacokinetics after intravenous administration in 186 individuals, and we determined the effect of sex; body mass index (BMI); previous and concomitant therapy with UGT1A substrates, inhibitors, and inducers; as well as common variations in the genes coding for UGT1A1, UGT1A6, and UGT1A9. We identified sex and UGT1A6 genetic variants as major factors influencing acetaminophen pharmacokinetics, with women showing lower clearance (p < 0.001) and higher area under the plasma drug concentration-time curve (AUC) values than men (p < 0.001). UGT1A6 genetic variants were related to decreased acetaminophen biodisposition. Individuals who were homozygous or double-heterozygous for variant UGT1A6 alleles showed a 22.5% increase in t1/2 values and a 22.8 increase in drug exposure (p < 0.001, and 0.006, respectively) after correction by sex. The effect is related to the UGT1A6*2 and UGT1A6*4 variant alleles, whereas no effect of UGT1A6*3 and UGT1A9*3 alleles, BMI, or drug−drug interaction was identified in this study. We conclude that sex and UGT1A6 variants determine acetaminophen pharmacokinetics, thus providing evidence to eventually developing pharmacogenomics procedures and recommendations for acetaminophen use.

Gender Variations in Pharmacokinetics of Paracetamol in Hausa/Fulani Ethnic group in Northwest Nigeria - A Two-stage Approach

Background:

Paracetamol is one of the most commonly used drugs worldwide and has been linked to drug-related liver damage, even when taken at recommended doses. Ingesting the upper limit of recommended doses of the drug produced a doubling of mortality when compared to not taking the drug. Acetaminophen ingestion has been implicated in the development of angioedema, the exasperation of asthma, and urticaria in patients with aspirin intolerance.

Aim:

This study aimed at assessing gender variations in the pharmacokinetics of paracetamol in Hausa/Fulani, the most populous ethnic group in Nigeria and determines a possibility of toxicity in the group.

Methods:

It was an exploratory study involving twenty participants selected by criterion sampling who satisfied inclusion criteria. They were fasted 11-h preceding acetaminophen administration to 3 h after administration. A single dose of acetaminophen, 1 g orally with 300 ml of distilled water, was administered at 8 A. M. Blood was obtained before the administration and 15, 30, and 45 min, and 1, 2, 3, 4, 5, and 6 h after the administration. Acetaminophen plasma concentrations were determined by validated reverse-phase high-performance liquid chromatography Food and Drug Administration guidelines.

Results:

Six out of 19 (31.6%) participants have higher than maximum therapeutic plasma concentration (>20 μg/ml). Pharmacokinetics parameters were higher in males except for clearance and volume of distribution.

Conclusion:

Clearance from the plasma tends to be more for females than their male counterparts. A good proportion of Hausa/Fulani is prone to acetaminophen toxicity at a therapeutic dose.

Mechanism of dasabuvir inhibition of acetaminophen glucuronidation

OBJECTIVES

Acetaminophen (APAP) (paracetamol) is a widely used non-prescription drug for pain relief and antipyretic effects. The clearance of APAP is mainly through phase-2 biotransformation catalysed by UDP-glucuronosyl transferases (UGT). Dasabuvir is an anti-hepatitis C drug reported to inhibit several UGT isoforms. The study evaluated the in-vitro inhibitory capacity of dasabuvir versus APAP glucuronidation.

METHODS

Procedures included human liver microsomal incubations with APAP and isoform-selective probe substrates.

KEY FINDINGS

Dasabuvir inhibited APAP metabolism by a reversible, mixed-type (competitive and non-competitive) partial inhibition, with an inhibition constant Ki = 3.4 µM. The index constant 'a' was 6.7, indicating the relative contribution of competitive and non-competitive inhibition. The enzyme-inhibitor complex was still able to catalyse the reaction by 12% of the control capacity. Dasabuvir produced strong partial inhibition effect of UGT1A1 and UGT1A9 and relatively complete inhibition of UGT1A6.

CONCLUSIONS

Consistent with previous reports, dasabuvir inhibits the activity of 3 UGT isoforms associated with APAP metabolism. In-vitro to in-vivo scaling by 2 different approaches showed identical results, predicting an increased AUC of APAP by a factor of 1.3-fold with coadministration of dasabuvir. Until the findings are confirmed in clinical drug interaction studies, APAP dosage should not exceed 3 g per day in dasabuvir-treated patients to avoid potentially hepatotoxic APAP exposures.

Individual variability in human urinary metabolites identifies age-related, body mass index-related, and sex-related biomarkers

Background

Metabolites present in human urine can be influenced by individual physiological parameters (e.g., body mass index [BMI], age, and sex). Observation of altered metabolites concentrations could provide insight into underlying disease pathology, disease prognosis and diagnosis, and facilitate discovery of novel biomarkers.

Methods

Quantitative metabolomics analysis in the urine of 183 healthy individuals was performed based on high‐resolution liquid chromatography–mass spectrometry (LC–MS). Coefficients of variation were obtained for 109 urine metabolites of all the 183 human healthy subjects.

Results

Three urine metabolites (such as dehydroepiandrosterone sulfate, acetaminophen glucuronide, and p‐anisic acid) with CV₁₈₃ > 0.3, for which metabolomics studies have been scarce, are considered highly variable here. We identified 30 age‐related metabolites, 18 BMI‐related metabolites, and 42 sex‐related metabolites. Among the identified metabolites, three metabolites were found to be associated with all three physiological parameters (age, BMI, and sex), which included dehydroepiandrosterone sulfate, 3‐methylcrotonylglycine and N‐acetyl‐aspartic acid. Pearson's coefficients demonstrated that some age‐, BMI‐, and sex‐related compounds are strongly correlated, suggesting that age, BMI, and sex could affect them concomitantly.

Conclusion

Metabolic differences between distinct physiological statuses were found to be related to several metabolic pathways (such as the caffeine metabolism, the amino acid metabolism, and the carbohydrate metabolism), and these findings may be key for the discovery of new diagnostics and treatments as well as new understandings on the mechanisms of some related diseases.

Using Pharmacogenetics of Direct Oral Anticoagulants to Predict Changes in Their Pharmacokinetics and the Risk of Adverse Drug Reactions

Dabigatran, rivaroxaban, apixaban, and edoxaban are direct oral anticoagulants (DOACs) that are increasingly used worldwide. Taking into account their widespread use for the prevention of thromboembolism in cardiology, neurology, orthopedics, and coronavirus disease 2019 (COVID 19) as well as their different pharmacokinetics and pharmacogenetics dependence, it is critical to explore new opportunities for DOACs administration and predict their dosage when used as monotherapy or in combination with other drugs. In this review, we describe the details of the relative pharmacogenetics on the pharmacokinetics of DOACs as well as new data concerning the clinical characteristics that predetermine the needed dosage and the risk of adverse drug reactions (ADRs). The usefulness of genetic information before and shortly after the initiation of DOACs is also discussed. The reasons for particular attention to these issues are not only new genetic knowledge and genotyping possibilities, but also the risk of serious ADRs (primarily, gastrointestinal bleeding). Taking into account the effect of the carriership of single nucleotide variants (SNVs) of genes encoding biotransformation enzymes and DOACs metabolism, the use of these measures is important to predict changes in pharmacokinetics and the risk of ADRs in patients with a high risk of thromboembolism who receive anticoagulant therapy.

Pharmacokinetics and Pharmacogenetics of Dabigatran

Dabigatran etexilate is a prodrug of dabigatran, a oral direct inhibitor of thrombin. Pharmacokinetics of dabigatran etexilate doesn’t have the disadvantages of vitamin K antagonists. However, pharmacokinetics and pharmacogenetics of dabigatran are variable. This can affect both effectiveness and safety of anticoagulant therapy. It is considered that CES1 enzyme and P-glycoprotein (CES1 and ABCB1 genes accordingly) play important role in pharmacokinetics of dabigatran etexilate. UDP-glucuronosyltransferase enzymes UGT2B15, UGT1A9, UGT2B7 (UGT2B15, UGT1A9, UGT2B7 genes accordingly) take part in the metabolism of active dabigatran. Presence of these gene’s single-nucleotide variants (SNV) can affect effectiveness and safety of dabigatran etexilate usage. The goal of this review is analysis of associated researches of SNV genes CES1 and ABCB1 and search for new candidate genes that reveal effectiveness and safety of dabigatran etexilate usage.

Materials and methods. The search for full-text publications in Russian and English languages containing key words “dabigatran etexilate”, “dabigatran”, “pharmacokinetics”, “effectiveness”, “safety” was carried out amongst literature of the past twenty years with the use of eLibrary, PubMed, Web of Science, OMIM data bases. Pharmacokinetics and pharmacogenetics of dabigatran etexilate are considered in this review. The hypothesis about UDP-glucuronosyltransferase enzymes influence on dabigatran metabolism was examined. Nowadays more than 2000 SNV CES1 and ABCB1 genes are identified, but their potential influence on pharmacokinetics of dabigatran etexilate and its active metabolite (dabigatran) in clinical practice needs to be further researched. Role of SNV UDP-glucuronosyltransferase genes (UGT2B15, UGT1A9, UGT2B7) in dabigatran’s effectiveness and safety is not explored enough. However, UGT2B15 gene can be a potential candidate gene for research on safety of this drug.

Comparison of the Pharmacokinetics of Generic Versus Branded Obeticholic Acid in a Chinese Population: Effects of Food and Sex

The present study assessed the pharmacokinetics and bioequivalence of a single 10-mg dose of a generic and the branded formulation (Ocaliva) of obeticholic acid (OCA) in healthy Chinese subjects under fasting and fed conditions. The possible effects of food and sex on the pharmacokinetics of OCA and its 2 active metabolites (glyco-OCA and tauro-OCA) were evaluated. Plasma concentrations of OCA and its 2 active metabolites were measured by liquid chromatography-tandem mass spectrometry. The 90%CIs of the ratios of the test and reference formulations for C_max , AUC_0-t , and AUC_0-∞ of OCA, glyco-OCA, and tauro-OCA were contained entirely within the 80% to 125% range required for bioequivalence under fasting and fed conditions. Plasma exposure of OCA was 30% to 36% higher under fed compared with fasting conditions. Plasma exposure of OCA, glyco-OCA, and tauro-OCA was 39% to 66%, 22% to 58%, and 37% to 84% higher, respectively, in women compared with men under fasting and fed conditions. In conclusion, OCA was well tolerated in healthy Chinese subjects under fasting and fed conditions. The single 10-mg dose of a generic OCA formulation was bioequivalent to Ocaliva. Food and sex impacted the pharmacokinetics of OCA and/or its 2 active metabolites. Further studies are required to determine if these effects are clinically relevant.

Human total clearance values and volumes of distribution of typical human cytochrome P450 2C9/19 substrates predicted by single-species allometric scaling using pharmacokinetic data sets from common marmosets genotyped for P450 2C19

Common marmosets (Callithrix jacchus) are small non-human primates that genetically lack cytochrome P450 2C9 (CYP2C9). Polymorphic marmoset CYP2C19 compensates by mediating oxidations of typical human CYP2C9/19 substrates.Twenty-four probe substrates were intravenously administered in combinations to marmosets assigned to extensive or poor metaboliser (PM) groups by CYP2C19 genotyping. Eliminations from plasma of cilomilast, phenytoin, repaglinide, tolbutamide, and S-warfarin in the CYP2C19 PM group were significantly slow; these drugs are known substrates of human CYP2C8/9/19.Human total clearance values and volumes of distribution of the 24 test compounds were extrapolated using single-species allometric scaling with experimental data from marmosets and found to be mostly comparable with the reported values.Human total clearance values and volumes of distribution of 15 of the 24 test compounds similarly extrapolated using reported data sets from cynomolgus or rhesus monkeys were comparable to the present predicted results, especially to those based on data from PM marmosets.These results suggest that single-species allometric scaling using marmosets, being small, has advantages over multiple-species-based allometry and could be applicable for pharmacokinetic predictions at the discovery stage of drug development.

Assessment of the biochemical pathways for acetaminophen toxicity: Implications for its carcinogenic hazard potential

In 2019 California's Office of Environmental Health Hazard Assessment (OEHHA) initiated a review of the carcinogenic hazard potential of acetaminophen. In parallel with this review, herein we evaluated the mechanistic data related to the steps and timing of cellular events following therapeutic recommended (≤4 g/day) and higher doses of acetaminophen that may cause hepatotoxicity to evaluate whether these changes indicate that acetaminophen is a carcinogenic hazard. At therapeutic recommended doses, acetaminophen forms limited amounts of N-acetyl-p-benzoquinone-imine (NAPQI) without adverse cellular effects. Following overdoses of acetaminophen, there is potential for more extensive formation of NAPQI and depletion of glutathione, which may result in mitochondrial dysfunction and DNA damage, but only at doses that result in cell death - thus making it implausible for acetaminophen to induce the kind of stable, genetic damage in the nucleus indicative of a genotoxic or carcinogenic hazard in humans. The collective data demonstrate a lack of a plausible mechanism related to carcinogenicity and are consistent with rodent cancer bioassays, epidemiological results reviewed in companion manuscripts in this issue, as well as conclusions of multiple international health authorities.

Human variability in isoform-specific UDP-glucuronosyltransferases: markers of acute and chronic exposure, polymorphisms and uncertainty factors

UDP-glucuronosyltransferases (UGTs) are involved in phase II conjugation reactions of xenobiotics and differences in their isoform activities result in interindividual kinetic differences of UGT probe substrates. Here, extensive literature searches were performed to identify probe substrates (14) for various UGT isoforms (UGT1A1, UGT1A3, UGT1A4, UGT1A6, UGT1A9, UGT2B7 and UGT2B15) and frequencies of human polymorphisms. Chemical-specific pharmacokinetic data were collected in a database to quantify interindividual differences in markers of acute (Cmax) and chronic (area under the curve, clearance) exposure. Using this database, UGT-related uncertainty factors were derived and compared to the default factor (i.e. 3.16) allowing for interindividual differences in kinetics. Overall, results show that pharmacokinetic data are predominantly available for Caucasian populations and scarce for other populations of different geographical ancestry. Furthermore, the relationships between UGT polymorphisms and pharmacokinetic parameters are rarely addressed in the included studies. The data show that UGT-related uncertainty factors were mostly below the default toxicokinetic uncertainty factor of 3.16, with the exception of five probe substrates (1-OH-midazolam, ezetimibe, raltegravir, SN38 and trifluoperazine), with three of these substrates being metabolised by the polymorphic isoform 1A1. Data gaps and future work to integrate UGT-related variability distributions with in vitro data to develop quantitative in vitro–in vivo extrapolations in chemical risk assessment are discussed.

Extensive literature search of human kinetic parameters for UGT probe substrates.

Bayesian meta-analysis quantifying human variability in acute and chronic kinetic parameters.

UGT isoform-related uncertainty factors were below the 3.16 kinetic default uncertainty factor for most probe substrates.

Quantifying human variability in UGT polymorphisms.

The Ontogeny of UDP-glucuronosyltransferase Enzymes, Recommendations for Future Profiling Studies and Application Through Physiologically Based Pharmacokinetic Modelling

Limited understanding of drug pharmacokinetics in children is one of the major challenges in paediatric drug development. This is most critical in neonates and infants owing to rapid changes in physiological functions, especially in the activity of drug-metabolising enzymes. Paediatric physiologically based pharmacokinetic models that integrate ontogeny functions for cytochrome P450 enzymes have aided our understanding of drug exposure in children, including those under the age of 2 years. Paediatric physiologically based pharmacokinetic models have consequently been recognised by the European Medicines Agency and the US Food and Drug Administration as innovative tools in paediatric drug development and regulatory decision making. However, little is currently known about age-related changes in UDP-glucuronosyltransferase-mediated metabolism, which represents the most important conjugation reaction for xenobiotics. Therefore, the objective of the review was to conduct a thorough literature survey to summarise our current understanding of age-related changes in UDP-glucuronosyltransferases as well as associated clinical and experimental sources of variance. Our findings indicate that there are distinct differences in UDP-glucuronosyltransferase expression and activity between isoforms for different age groups. In addition, there is substantial variability between individuals and laboratories reported for human liver microsomes, which results in part from a lack of standardised experimental conditions. Therefore, we provide a number of best practice recommendations for experimental conditions, which ultimately may help improve the quality of data used for quantitative clinical pharmacology approaches, and thus for safe and effective pharmacotherapy in children.

The Impact of Proximal Roux-en-Y Gastric Bypass Surgery on Acetaminophen Absorption and Metabolism

BACKGROUND

Roux-en-Y gastric bypass (RYGBS), a surgery that creates a smaller stomach pouch and reduces the length of small intestine, is one of the most common medical interventions for the treatment of obesity.

AIM

The aim of this study was to determine how RYGBS affects the absorption and metabolism of acetaminophen.

MATERIALS AND METHODS

Ten morbidly obese patients received 1.5 g of liquid acetaminophen (APAP) orally on three separate pharmacokinetic study days (i.e., pre-RYGBS baseline and 3 and 12 months post-RYGBS). Plasma was collected at pre-specified timepoints over 24 hours, and the samples were analyzed using liquid chromatography-mass spectrometry for APAP, APAPglucuronide (APAP-gluc), APAP-sulfate (APAP-sulf), APAP-cysteine (APAP-cys), and APAP-Nacetylcysteine (APAP-nac).

RESULT

Following RYGBS, peak APAP concentrations at the 3-month and 12-month visits increased by 2.0-fold compared to baseline (p=0.0039 and p=0.0078, respectively) and the median time to peak concentration decreased from 35 to 10 minutes. In contrast, peak concentrations of APAP-gluc, APAP-sulf, APAP-cys, and APAP-nac were unchanged following RYGBS. The apparent oral clearance of APAP and the ratios of metabolite area under the curve (AUC)-to-APAP AUC for all four metabolites decreased at 3 and 12 months post-RYGBS compared to the presurgical baseline. In a simulation of expected steady-state plasma concentrations following multiple dosing of 650 mg APAP every 4 hours, post-RYGBS patients had higher steady-state peak APAP concentrations compared to healthy individuals and obese pre-RYGBS patients, though APAP exposure was unchanged compared to healthy individuals.

CONCLUSION

Following RYGBS, the rate and extent of APAP absorption increased and decreased formation of APAP metabolites was observed, possibly due to downregulation of Phase II and cytochrome P450 2E1 enzymes.

Coordinated Regulation of UGT2B15 Expression by Long Noncoding RNA LINC00574 and hsa-miR-129-5p in HepaRG Cells

Recent studies have shown that microRNAs and long noncoding RNAs (lncRNAs) regulate the expression of drug metabolizing enzymes (DMEs) in human hepatic cells and that a set of DMEs, including UDP glucuronosyltransferase (UGT) 2B15, is down-regulated dramatically in liver cells by toxic acetaminophen (APAP) concentrations. In this study we analyzed mRNA, microRNA, and lncRNA expression profiles in APAP-treated HepaRG cells to explore noncoding RNA-dependent regulation of DME expression. The expression of UGT2B15 and lncRNA LINC00574 was decreased in APAP-treated HepaRG cells. UGT2B15 levels were diminished by LINC00574 suppression using antisense oligonucleotides or small interfering RNA. Furthermore, we found that hsa-miR-129-5p suppressed LINC00574 and decreased UGT2B15 expression via LINC00574 in HepaRG cells. In conclusion, our results indicate that LINC00574 acts as an important regulator of UGT2B15 expression in human hepatic cells, providing experimental evidence and new clues to understand the role of cross-talk between noncoding RNAs. SIGNIFICANCE STATEMENT: We showed a molecular network that displays the cross-talk and consequences among mRNA, micro RNA, long noncoding RNA, and proteins in acetaminophen (APAP)-treated HepaRG cells. APAP treatment increased the level of hsa-miR-129-5p and decreased that of LINC00574, ultimately decreasing the production of UDP glucuronosyltransferase (UGT) 2B15. The proposed regulatory network suppresses UGT2B15 expression through interaction of hsa-miR-129-5p and LINC00574, which may be achieved potentially by recruiting RNA binding proteins.

Knockdown of Long Noncoding RNAs Hepatocyte Nuclear Factor 1α Antisense RNA 1 and Hepatocyte Nuclear Factor 4α Antisense RNA 1 Alters Susceptibility of Acetaminophen-Induced Cytotoxicity in HepaRG Cells

Acetaminophen (APAP) is a commonly used over-the-counter drug for its analgesic and antipyretic effects. However, APAP overdose leads to severe APAP-induced liver injury (AILI) and even death as a result of the accumulation of N-acetyl-p-benzoquinone imine, the toxic metabolite of APAP generated by cytochrome P450s (P450s). Long noncoding RNAs HNF1α antisense RNA 1 (HNF1α-AS1) and HNF4α antisense RNA 1 (HNF4α-AS1) are regulatory RNAs involved in the regulation of P450 expression in both mRNA and protein levels. This study aims to determine the impact of HNF1α-AS1 and HNF4α-AS1 on AILI. Small hairpin RNAs were used to knock down HNF1α-AS1 and HNF4α-AS1 in HepaRG cells. Knockdown of these lncRNAs altered APAP-induced cytotoxicity, indicated by MTT and LDH assays. Specifically, HNF1α-AS1 knockdown decreased APAP toxicity with increased cell viability and decreased LDH release, whereas HNF4α-AS1 knockdown exacerbated APAP toxicity, with opposite effects in the MTT and LDH assays. Alterations on gene expression by knockdown of HNF1α-AS1 and HNF4α-AS1 were examined in several APAP metabolic pathways, including CYP1A2, CYP2E1, CYP3A4, UGT1A1, UGT1A9, SULT1A1, GSTP1, and GSTT1. Knockdown of HNF1α-AS1 decreased mRNA expression of CYP1A2, 2E1, and 3A4 by 0.71-fold, 0.35-fold, and 0.31-fold, respectively, whereas knockdown of HNF4α-AS1 induced mRNAs of CYP1A2, 2E1, and 3A4 by 1.3-fold, 1.95-fold, and 1.9-fold, respectively. These changes were also observed in protein levels. Knockdown of HNF1α-AS1 and HNF4α-AS1 had limited effects on the mRNA expression of UGT1A1, UGT1A9, SULT1A1, GSTP1, and GSTT1. Altogether, our study suggests that HNF1α-AS1 and HNF4α-AS1 affected AILI mainly through alterations of P450-mediated APAP biotransformation in HepaRG cells, indicating an important role of the lncRNAs in AILI. SIGNIFICANCE STATEMENT: The current research identified two lncRNAs, hepatocyte nuclear factor 1α antisense RNA 1 and hepatocyte nuclear factor 4α antisense RNA 1, which were able to affect susceptibility of acetaminophen (APAP)-induced liver injury in HepaRG cells, possibly through regulating the expression of APAP-metabolizing cytochrome P450 enzymes. This discovery added new factors, lncRNAs, which can be used to predict cytochrome P450-mediated drug metabolism and drug-induced toxicity.

Fatal liver failure after therapeutic doses of paracetamol in a patient with Duchenne muscular dystrophy and atypical pharmacogenetic profile of drug-metabolizing enzymes

Paracetamol has a good safety profile, but pharmacogenetic differences in drug-metabolizing enzymes may have an impact on its risk of hepatotoxicity. We present a case of fatal acute liver failure (ALF) after therapeutic doses of paracetamol in a patient with Duchenne muscular dystrophy, where pharmacogenetic screening was conducted. This 30-year-old man was electively admitted for a tracheostomy. A total of 14.5 g paracetamol was given over four days. He developed a severe ALF and died 11 days after admission. Pharmacogenetic screening showed absent CYP2D6 metabolism and increased CYP1A2 activity, which may have increased the formation of toxic intermediate metabolite, N-acetyl-p-benzo-quinone imine (NAPQI). He also had decreased function of UGT2B15, which increases the amount of paracetamol available for metabolism to NAPQI. Having a reduced muscle mass and thus a reduced glutathione levels to detoxify produced NAPQI may add to the risk of toxicity. This case may indicate that pharmacogenetic variability is of potential relevance for the risk of paracetamol-induced hepatotoxicity in patients with neuromuscular diseases. Further studies should investigate if pharmacogenetic screening could be a tool to detect potentially increased risk of hepatotoxicity in these patients at therapeutic doses of paracetamol and hence provide information for selection of analgesic treatment.

Adducts Post Acetaminophen Overdose Treated with a 12-Hour vs 20-Hour Acetylcysteine Infusion

INTRODUCTION

Acetaminophen protein adducts in the circulation are a specific biomarker of acetaminophen oxidation, and may be a more sensitive measure of impending hepatic injury following overdose than alanine transaminase (ALT). We performed an exploratory analytical substudy of adducts during a clinical trial (NACSTOP) of abbreviated (12-hour) versus control (20-hour) acetylcysteine to identify any signal of diminished antidotal effectiveness with shortened therapy.

METHODS

We measured adducts at 0, 12, and 20 hours from a convenience sample of subjects enrolled in the cluster-controlled NACSTOP trial evaluating a 12-hour ("abbreviated"; 200 mg/kg over 4 hours, 50 mg/kg over 8 hours) vs 20-hour acetylcysteine regimen ("control"; 200 mg/kg over 4 hours, 100 mg/kg over 16 hours). Adducts were assayed using high-performance liquid chromatography/mass spectrometry.

RESULTS

Median ALT 20 hours after the initiation of acetylcysteine was 12 U/L (IQR 8,14) in the abbreviated 12-hour regimen group (N = 8), compared with the control group 16 U/L (IQR 11,21; N = 21) (p = 0.46). Adduct concentrations were similarly low in both groups: abbreviated [(0.005 μmol/L, IQR (0,0.14)] and control [(0.005 μmol/L, IQR (0,0.05)] (p = 0.61).

CONCLUSIONS

There were minimal to no acetaminophen protein adducts detected. These findings further support discontinuing acetylcysteine when acetaminophen concentrations are low and liver function tests normal after 12 hours of treatment.

Ontogeny of Hepatic Sulfotransferases and Prediction of Age-Dependent Fractional Contribution of Sulfation in Acetaminophen Metabolism

Cytosolic sulfotransferases (SULTs), including SULT1A, SULT1B, SULT1E, and SULT2A isoforms, play noteworthy roles in xenobiotic and endobiotic metabolism. We quantified the protein abundances of SULT1A1, SULT1A3, SULT1B1, and SULT2A1 in human liver cytosol samples (n = 194) by liquid chromatography-tandem mass spectrometry proteomics. The data were analyzed for their associations by age, sex, genotype, and ethnicity of the donors. SULT1A1, SULT1B1, and SULT2A1 showed significant age-dependent protein abundance, whereas SULT1A3 was invariable across 0-70 years. The respective mean abundances of SULT1A1, SULT1B1, and SULT2A1 in neonatal samples was 24%, 19%, and 38% of the adult levels. Interestingly, unlike UDP-glucuronosyltransferases and cytochrome P450 enzymes, SULT1A1 and SULT2A1 showed the highest abundance during early childhood (1 to <6 years), which gradually decreased by approx. 40% in adolescents and adults. SULT1A3 and SULT1B1 abundances were significantly lower in African Americans compared with Caucasians. Multiple linear regression analysis further confirmed the association of SULT abundances by age, ethnicity, and genotype. To demonstrate clinical application of the characteristic SULT ontogeny profiles, we developed and validated a proteomics-informed physiologically based pharmacokinetic model of acetaminophen. The latter confirmed the higher fractional contribution of sulfation over glucuronidation in the metabolism of acetaminophen in children. The study thus highlights that the ontogeny-based age-dependent fractional contribution (fm) of individual drug-metabolizing enzymes has better potential in prediction of drug-drug interactions and the effect of genetic polymorphisms in the pediatric population.

Acetaminophen Hepatotoxicity

Acetaminophen (APAP) is one of the most popular and safe pain medications worldwide. However, due to its wide availability, it is frequently implicated in intentional or unintentional overdoses where it can cause severe liver injury and even acute liver failure (ALF). In fact, APAP toxicity is responsible for 46% of all ALF cases in the United States. Early mechanistic studies in mice demonstrated the formation of a reactive metabolite, which is responsible for hepatic glutathione depletion and initiation of the toxicity. This insight led to the rapid introduction of N-acetylcysteine as a clinical antidote. However, more recently, substantial progress was made in further elucidating the detailed mechanisms of APAP-induced cell death. Mitochondrial protein adducts trigger a mitochondrial oxidant stress, which requires amplification through a MAPK cascade that ultimately results in activation of c-jun N-terminal kinase (JNK) in the cytosol and translocation of phospho-JNK to the mitochondria. The enhanced oxidant stress is responsible for the membrane permeability transition pore opening and the membrane potential breakdown. The ensuing matrix swelling causes the release of intermembrane proteins such as endonuclease G, which translocate to the nucleus and induce DNA fragmentation. These pathophysiological signaling mechanisms can be additionally modulated by removing damaged mitochondria by autophagy and replacing them by mitochondrial biogenesis. Importantly, most of the mechanisms have been confirmed in human hepatocytes and indirectly through biomarkers in plasma of APAP overdose patients. The extensive necrosis caused by APAP overdose leads to a sterile inflammatory response. Although recruitment of inflammatory cells is necessary for removal of cell debris in preparation for regeneration, these cells have the potential to aggravate the injury. This review touches on the newest insight into the intracellular mechanisms of APAP-induced cells death and the resulting inflammatory response. Furthermore, it discusses the translation of these findings to humans and the emergence of new therapeutic interventions.

Genomics Testing and Personalized Medicine in the Preoperative Setting

Pharmacogenomics (PGx) is the study of how individuals' personal genotypes may affect their responses to various pharmacologic agents. The application of PGx principles in perioperative medicine is fairly novel. Challenges in executing PGx programs into health care systems include physician buy-in and integration into usual clinical workflow, including the electronic health record. This article discusses the current evidence highlighting the potential of PGx with various drug categories (including opioids, nonopioid analgesics, sedatives, β-blockers, antiemetics, and anticoagulants) used in the perioperative process and the challenges of integrating PGx into a health care system and relevant workflows.

Cardiovascular Pharmacogenomics: Does It Matter If You're Black or White?

Race and ancestry have long been associated with differential risk and outcomes to disease as well as responses to medications. These differences in drug response are multifactorial with some portion associated with genomic variation. The field of pharmacogenomics aims to predict drug response in patients prior to medication administration and to uncover the biological underpinnings of drug response. The field of human genetics has long recognized that genetic variation differs in frequency between ancestral populations, with some single nucleotide polymorphisms found solely in one population. Thus far, most pharmacogenomic studies have focused on individuals of European and East Asian ancestry, resulting in a substantial disparity in the clinical utility of genetic prediction for drug response in US minority populations. In this review, we discuss the genetic factors that underlie variability to drug response and known pharmacogenomic associations and how these differ between populations, with an emphasis on the current knowledge in cardiovascular pharmacogenomics.

Racial and Ethnic Disparities in Treatment Outcomes of Patients with Ruptured or Unruptured Intracranial Aneurysms

OBJECTIVE

The aim of this study is to examine how health outcomes varied by treatment selection and race/ethnicity among hospitalized US patients with ruptured or unruptured IAs.

METHODS

A retrospective cohort study was conducted using a sample of 62,224 hospital discharges from the 2002-2012 Nationwide Inpatient Sample. Logistic regression models evaluated treatment selection as predictor of in-hospital survival (IHS: "yes," "no") and length of stay (LOS ≤ 7 days, > 7 days), overall and across racial/ethnic groups, taking hospital- and patient-level confounders into account, while stratifying by IA rupture status.

RESULTS

Compared to surgical clipping, endovascular coiling was associated with better IHS, after controlling for confounders. Compared to surgical clipping, LOS ≤ 7 days was less likely in patients with combination of treatments and more likely among patients with endovascular coiling as well as balloon- or stent-assisted coiling. Observed relationships varied significantly by race and ethnicity for IHS, but not for LOS ≤ 7 days. Whereas combination of treatments were associated with worse IHS than surgical clipping among Blacks alone, endovascular coiling was associated with better IHS than surgical clipping among White and Other racial/ethnic subgroups. These relationships were for the most part consistent among patients with and without IA rupture.

CONCLUSIONS

Racial and ethnic subgroups of IA patients experienced differential IHS by treatment selection, irrespective of IA rupture status. Prospective cohort studies are needed to further elucidate these racial and ethnic disparities, while collecting data on IA size, location, and morphology as well as Hunt and Hess grade for ruptured IA.

Inhibition of CYP2E1 With Propylene Glycol Does Not Protect Against Hepatocellular Injury in Human Acetaminophen Daily-Dosing Model

Acetaminophen (APAP)-induced liver injury is initiated by metabolism of APAP by the cytochrome P-450 (CYP) system, primarily CYP2E1. We previously demonstrated CYP inhibition following administration of a liquid APAP formulation containing propylene glycol, a CYP2E1 inhibitor, and other excipients. This study was undertaken to determine if propylene glycol specifically inhibits production of CYP-derived metabolites and if propylene glycol reduces the rise in alanine aminotransferase (ALT) seen following prolonged APAP dosing. Human subjects were randomized to receive 4 g of APAP daily in one arm of the study or 4 g of APAP with 5 mL of 99% propylene glycol in the other arm, both for 14 days. After a washout period of at least 14 days, subjects were crossed over between arms. Outcomes were rise of ALT greater than 2 times baseline (responders) and proportion of randomly sampled CYP-derived metabolites relative to total metabolites produced. There was no difference in percentage of responders between treatment groups: 6 of 21 in the APAP group (29%) compared with 8 of 20 in the APAP + propylene glycol group (40%); chi-square, P = .59. For all subjects, the mean percentage of CYP-derived metabolites produced was 5.8% (APAP) versus 4.3% (APAP + propylene glycol); P = .018. This effect was solely attributable to the responders: the mean percentage of CYP metabolites of responders was 7.7% (APAP) versus 4.6% (APAP + propylene glycol), P = .050, whereas there was no difference for the nonresponders. Five subjects were responders in both arms (2% probability of random occurrence). Our data indicates that propylene glycol inhibits CYP2E1 metabolism of APAP in some subjects but does not effect hepatocellular indury at the dose given.

Biomarkers of drug-induced liver injury: progress and utility in research, medicine, and regulation

INTRODUCTION

The difficulty of understanding and diagnosing drug-induced liver injury (DILI) has led to proliferation of serum and genetic biomarkers. Many applications of these biomarkers have been proposed, including investigation of mechanisms, prediction of DILI during early trials or before initiation of therapy in patients, and diagnosis of DILI during therapy. Areas covered: We review the definition and categories of DILI, describe recent developments in DILI biomarker development, and provide guidance for future directions in DILI biomarker research. Expert commentary: There are major obstacles to DILI biomarker development and implementation, including the low prevalence of idiosyncratic DILI (IDILI), weak associations of IDILI with genetic variants, and lack of specificity of many biomarkers for the liver. Certain serum biomarkers, like miR-122, may have clinical utility in early-presenting patients with either intrinsic or idiosyncratic DILI in the future, while others likely will not find use. Future research should focus on implementation of biomarkers to predict later injury and outcome in early presenters with intrinsic DILI, and on development of biomarkers of adaptation and repair in the liver that can be used to determine if a liver test abnormality is likely to be clinically significant in IDILI.

Genetic Association of Single Nucleotide Polymorphisms with Acetaminophen-Induced Hepatotoxicity

Acetaminophen is commonly used to reduce pain and fever. Unfortunately, overdose of acetaminophen is a leading cause of acute liver injury and failure in many developed countries. The majority of acetaminophen is safely metabolized in the liver and excreted in the urine; however, a small percentage is converted to the highly reactive N-acetyl-p-benzoquinone imine (NAPQI). At therapeutic doses, NAPQI is inactivated by glutathione S-transferases, but at toxic levels, excess NAPQI forms reactive protein adducts that lead to hepatotoxicity. Individual variability in the response to both therapeutic and toxic levels of acetaminophen suggests a genetic component is involved in acetaminophen metabolism. In this review, we evaluate the genetic association studies that have identified 147 single nucleotide polymorphisms linked to acetaminophen-induced hepatotoxicity. The identification of novel genetic markers for acetaminophen-induced hepatotoxicity provides a rich resource for further evaluation and may lead to improved prognosis, prevention, and treatment.

Association Between Early Postoperative Acetaminophen Exposure and Acute Kidney Injury in Pediatric Patients Undergoing Cardiac Surgery

IMPORTANCE

Acute kidney injury (AKI) is a common and serious complication for pediatric cardiac surgery patients associated with increased morbidity, mortality, and length of stay. Current strategies focus on risk reduction and early identification because there are no known preventive or therapeutic agents. Cardiac surgery and cardiopulmonary bypass lyse erythrocytes, releasing free hemoglobin and contributing to oxidative injury. Acetaminophen may prevent AKI by reducing the oxidation state of free hemoglobin.

OBJECTIVE

To test the hypothesis that early postoperative acetaminophen exposure is associated with reduced risk of AKI in pediatric patients undergoing cardiac surgery.

DESIGN, SETTING, AND PARTICIPANTS

In this retrospective cohort study, the setting was 2 tertiary referral children's hospitals. The primary and validation cohorts included children older than 28 days admitted for cardiac surgery between July 1, 2008, and June 1, 2016. Exclusion criteria were postoperative extracorporeal membrane oxygenation and inadequate serum creatinine measurements to determine AKI status.

EXPOSURES

Acetaminophen exposure in the first 48 postoperative hours.

MAIN OUTCOMES AND MEASURES

Acute kidney injury based on Kidney Disease: Improving Global Outcomes serum creatinine criteria (increase by ≥0.3 mg/dL from baseline or at least 1.5-fold more than the baseline [to convert to micromoles per liter, multiply by 88.4]) in the first postoperative week.

RESULTS

The primary cohort (n = 666) had a median age of 6.5 (interquartile range [IQR], 3.9-44.7) months, and 341 (51.2%) had AKI. In unadjusted analyses, those with AKI had lower median acetaminophen doses than those without AKI (47 [IQR, 16-88] vs 78 [IQR, 43-104] mg/kg, P < .001). In logistic regression analysis adjusting for age, cardiopulmonary bypass time, red blood cell distribution width, postoperative hypotension, nephrotoxin exposure, and Risk Adjustment for Congenital Heart Surgery score, acetaminophen exposure was protective against postoperative AKI (odds ratio, 0.86 [95% CI, 0.82-0.90] per each additional 10 mg/kg). Findings were replicated in the validation cohort (n = 333), who had a median age of 14.1 (IQR, 3.9-158.2) months, and 162 (48.6%) had AKI. Acetaminophen doses were 60 (95% CI, 40-87) mg/kg in those with AKI vs 70 (95% CI, 45-94) mg/kg in those without AKI (P = .03), with an adjusted odds ratio of 0.91 (95% CI, 0.84-0.99) for each additional 10 mg/kg.

CONCLUSIONS AND RELEVANCE

These results indicate that early postoperative acetaminophen exposure may be associated with a lower rate of AKI in pediatric patients who undergo cardiac surgery. Further analysis to validate these findings, potentially through a prospective, randomized trial, may establish acetaminophen as a preventive agent for AKI.

Bioequivalence Evaluation of Two Oral Formulations of Acetaminophen in Healthy Subjects: Results From a Randomized, Single-Blind, Crossover Study

Despite widespread availability of acetaminophen in Mexico, data on its pharmacokinetic properties in Mexican populations are limited. This single‐center, single‐blind, randomized, 2‐period, 2‐treatment, crossover, single‐dose‐per‐period, 2‐sequence study evaluated the bioequivalence of a test acetaminophen product available in Mexico compared with a reference 500‐mg acetaminophen product in 28 healthy adults under fasting conditions. Blood samples were collected predose and at specified intervals across a 16‐hour period following administration and were analyzed for acetaminophen using a validated reverse‐phase high‐performance liquid chromatography method. Drug products were considered to be bioequivalent if confidence intervals of natural log‐transformed C_max, AUC_0‐t, and AUC_0‐∞ data were within the range of 80% to 125%. Results were inconclusive for C_max due to high levels of intrasubject variability with this parameter. However, criteria for bioequivalence were met for AUC_0‐t and AUC_0‐∞. All measured acetaminophen concentrations in this study were within a safe therapeutic range, and no adverse events were reported. The level of C_max intrasubject variability observed in this study does not have any apparent clinical implications that could affect either safety or efficacy.

Acetaminophen Toxicity: Novel Insights Into Mechanisms and Future Perspectives

Acetaminophen (APAP) overdose is the most common cause of acute liver failure in the US, and decades of intense study of its pathogenesis resulted in the development of the antidote N-acetylcysteine, which facilitates scavenging of the reactive metabolite and is the only treatment in clinical use. However, the narrow therapeutic window of this intervention necessitates a better understanding of the intricacies of APAP-induced liver injury for the development of additional therapeutic approaches that can benefit late-presenting patients. More recent investigations into APAP hepatotoxicity have established the critical role of mitochondrial dysfunction in mediating liver injury as well as clarified mechanisms of APAP-induced hepatocyte cell death. Thus, it is now established that mitochondrial oxidative and nitrosative stress is a key mechanistic feature involved in downstream signaling after APAP overdose. The identification of specific mediators of necrotic cell death further establishes the regulated nature of APAP-induced hepatocyte cell death. In addition, the discovery of the role of mitochondrial dynamics and autophagy in APAP-induced liver injury provides additional insight into the elaborate cell signaling mechanisms involved in the pathogenesis of this important clinical problem. In spite of these new insights into the mechanisms of liver injury, significant controversy still exists on the role of innate immunity in APAP-induced hepatotoxicity.