B. Kevin Park

Adverse drug reactions as cause of admission to hospital: prospective analysis of 18 820 patients

Abstract Objective To ascertain the current burden of adverse drug reactions (ADRs) through a prospective analysis of all admissions to hospital. Design Prospective observational study. Setting Two large general hospitals in Merseyside, England. Participants 18 820 patients aged > 16 years admitted over six months and assessed for cause of admission. Main outcome measures Prevalence of admissions due to an ADR, length of stay, avoidability, and outcome. Results There were 1225 admissions related to an ADR, giving a prevalence of 6.5%, with the ADR directly leading to the admission in 80% of cases. The median bed stay was eight days, accounting for 4% of the hospital bed capacity. The projected annual cost of such admissions to the NHS is £466m (€706m,

HLA-B*5701 genotype is a major determinant of drug-induced liver injury due to flucloxacillin

847m). The overall fatality was 0.15%. Most reactions were either definitely or possibly avoidable. Drugs most commonly implicated in causing these admissions included low dose aspirin, diuretics, warfarin, and non-steroidal anti-inflammatory drugs other than aspirin, the most common reaction being gastrointestinal bleeding. Conclusion The burden of ADRs on the NHS is high, accounting for considerable morbidity, mortality, and extra costs. Although many of the implicated drugs have proved benefit, measures need to be put into place to reduce the burden of ADRs and thereby further improve the benefit:harm ratio of the drugs.

HLA-A*3101 and Carbamazepine-Induced Hypersensitivity Reactions in Europeans

Drug-induced liver injury (DILI) is an important cause of serious liver disease. The antimicrobial agent flucloxacillin is a common cause of DILI, but the genetic basis for susceptibility remains unclear. We conducted a genome-wide association (GWA) study using 866,399 markers in 51 cases of flucloxacillin DILI and 282 controls matched for sex and ancestry. The GWA showed an association peak in the major histocompatibility complex (MHC) region with the strongest association (P = 8.7 × 10−33) seen for rs2395029[G], a marker in complete linkage disequilibrium (LD) with HLA-B*5701. Further MHC genotyping, which included 64 flucloxacillin-tolerant controls, confirmed the association with HLA-B*5701 (OR = 80.6, P = 9.0 × 10−19). The association was replicated in a second cohort of 23 cases. In HLA-B*5701 carrier cases, rs10937275 in ST6GAL1 on chromosome 3 also showed genome-wide significance (OR = 4.1, P = 1.4 × 10−8). These findings provide new insights into the mechanism of flucloxacillin DILI and have the potential to substantially improve diagnosis of this serious disease.

The Nrf2 cell defence pathway: Keap1-dependent and -independent mechanisms of regulation.

BACKGROUND Carbamazepine causes various forms of hypersensitivity reactions, ranging from maculopapular exanthema to severe blistering reactions. The HLA-B*1502 allele has been shown to be strongly correlated with carbamazepine-induced Stevens-Johnson syndrome and toxic epidermal necrolysis (SJS-TEN) in the Han Chinese and other Asian populations but not in European populations. METHODS We performed a genomewide association study of samples obtained from 22 subjects with carbamazepine-induced hypersensitivity syndrome, 43 subjects with carbamazepine-induced maculopapular exanthema, and 3987 control subjects, all of European descent. We tested for an association between disease and HLA alleles through proxy single-nucleotide polymorphisms and imputation, confirming associations by high-resolution sequence-based HLA typing. We replicated the associations in samples from 145 subjects with carbamazepine-induced hypersensitivity reactions. RESULTS The HLA-A*3101 allele, which has a prevalence of 2 to 5% in Northern European populations, was significantly associated with the hypersensitivity syndrome (P=3.5×10(-8)). An independent genomewide association study of samples from subjects with maculopapular exanthema also showed an association with the HLA-A*3101 allele (P=1.1×10(-6)). Follow-up genotyping confirmed the variant as a risk factor for the hypersensitivity syndrome (odds ratio, 12.41; 95% confidence interval [CI], 1.27 to 121.03), maculopapular exanthema (odds ratio, 8.33; 95% CI, 3.59 to 19.36), and SJS-TEN (odds ratio, 25.93; 95% CI, 4.93 to 116.18). CONCLUSIONS The presence of the HLA-A*3101 allele was associated with carbamazepine-induced hypersensitivity reactions among subjects of Northern European ancestry. The presence of the allele increased the risk from 5.0% to 26.0%, whereas its absence reduced the risk from 5.0% to 3.8%. (Funded by the U.K. Department of Health and others.).

Circulating microRNAs as potential markers of human drug‐induced liver injury

The transcription factor Nrf2 (NF-E2-related factor 2) plays a vital role in maintaining cellular homeostasis, especially upon the exposure of cells to chemical or oxidative stress, through its ability to regulate the basal and inducible expression of a multitude of antioxidant proteins, detoxification enzymes and xenobiotic transporters. In addition, Nrf2 contributes to diverse cellular functions including differentiation, proliferation, inflammation and lipid synthesis and there is an increasing association of aberrant expression and/or function of Nrf2 with pathologies including cancer, neurodegeneration and cardiovascular disease. The activity of Nrf2 is primarily regulated via its interaction with Keap1 (Kelch-like ECH-associated protein 1), which directs the transcription factor for proteasomal degradation. Although it is generally accepted that modification (e.g. chemical adduction, oxidation, nitrosylation or glutathionylation) of one or more critical cysteine residues in Keap1 represents a likely chemico-biological trigger for the activation of Nrf2, unequivocal evidence for such a phenomenon remains elusive. An increasing body of literature has revealed alternative mechanisms of Nrf2 regulation, including phosphorylation of Nrf2 by various protein kinases (PKC, PI3K/Akt, GSK-3β, JNK), interaction with other protein partners (p21, caveolin-1) and epigenetic factors (micro-RNAs -144, -28 and -200a, and promoter methylation). These and other processes are potentially important determinants of Nrf2 activity, and therefore may contribute to the maintenance of cellular homeostasis. Here, we dissect evidence supporting these Keap1-dependent and -independent mechanisms of Nrf2 regulation. Furthermore, we highlight key knowledge gaps in this important field of biology, and suggest how these may be addressed experimentally.

Genetic susceptibility to adverse drug reactions

New biomarkers of liver injury are required in the clinic and in preclinical pharmaceutical evaluation. Previous studies demonstrate that two liver‐enriched microRNAs (miR‐122 and miR‐192) are promising biomarkers of acetaminophen‐induced acute liver injury (APAP‐ALI) in mice. We have examined these molecules, for the first time, in humans with APAP poisoning. Serum miR‐122 and miR‐192 were substantially higher in APAP‐ALI patients, compared to healthy controls (median ΔΔCt [25th, 75th percentile]) (miR‐122: 1,265 [491, 4,270] versus 12.1 [7.0, 26.9], P < 0.0001; miR‐192: 6.9 [2.0, 29.2] versus 0.44 [0.30, 0.69], P < 0.0001). A heart‐enriched miR‐1 showed no difference between APAP‐ALI patients and controls, whereas miR‐218 (brain‐enriched) was slightly higher in the APAP‐ALI cohort (0.17 [0.07, 0.50] versus 0.07 [0.04, 0.12]; P = 0.01). In chronic kidney disease (CKD) patients, miR‐122 and ‐192 were modestly higher, compared to controls (miR‐122: 32.0 [21.1, 40.9] versus 12.1 [7.0, 26.9], P = 0.006; miR‐192: 1.2 [0.74, 1.9] versus 0.44 [0.30, 0.69], P = 0.005), but miR‐122 and ‐192 were substantially higher in APAP‐ALI patients than CKD patients (miR‐122: P < 0.0001; miR‐192: P < 0.0004). miR‐122 correlated with peak ALT levels in the APAP‐ALI cohort (Pearson R = 0.46, P = 0.0005), but not with prothrombin time. miR‐122 was also raised alongside peak ALT levels in a group of patients with non‐APAP ALI. Day 1 serum miR‐122 levels were almost 2‐fold higher in APAP‐ALI patients who satisfied Kings College Criteria (KCC), compared to those who did not satisfy KCC, although this did not reach statistical significance (P = 0.15). Conclusion: This work provides the first evidence for the potential use of miRNAs as biomarkers of human drug‐induced liver injury. (HEPATOLOGY 2011;)

Multiple reaction monitoring for quantitative biomarker analysis in proteomics and metabolomics

Adverse drug reactions (ADRs) are a major clinical problem. Genetic factors can determine individual susceptibility to both dose-dependent and dose-independent ADRs. Determinants of susceptibility include kinetic factors, such as gene polymorphisms in cytochrome P450 enzymes, and dynamic factors, such as polymorphisms in drug targets. The relative importance of these factors will depend on the nature of the ADR; however, it is likely that more than one gene will be involved in most instances. In the future, whole genome single nucleotide polymorphism (SNP) profiling might allow an unbiased method of determining genetic predisposing factors for ADRs, but might be limited by the lack of adequate numbers of patient samples. The overall clinical utility of genotyping in preventing ADRs needs to be proven by the use of prospective randomized controlled clinical trials.

Managing the challenge of chemically reactive metabolites in drug development

The conventional pipeline for biomarker development involves a discovery phase, typically conducted by mass spectrometry (MS), followed by validation and clinical application, usually on an alternative platform, such as immunoassay. Whilst this approach is suitable for the development of single biomarkers, with the current drive towards larger panels of multiplexed biomarkers, the process becomes inefficient and costly. Consequently, the emphasis is now shifting towards performing full biomarker discovery, qualification and quantification on the same technology platform. The ease of multiplexing and ability to determine protein modifications makes MS an attractive alternative to antibody-based technologies. In addition, developments in quantitative MS, through the application of stable isotope labelling and scanning techniques, such as multiple reaction monitoring (MRM), have greatly enhanced both the specificity and sensitivity of MS-based assays to the point that they can rival immunoassay for some analytes. This review focuses on the application of MRM for quantitative MS analysis, particularly with respect to proteins and peptides.

Fortnightly review: Adverse drug reactions

The normal metabolism of drugs can generate metabolites that have intrinsic chemical reactivity towards cellular molecules, and therefore have the potential to alter biological function and initiate serious adverse drug reactions. Here, we present an assessment of the current approaches used for the evaluation of chemically reactive metabolites. We also describe how these approaches are being used within the pharmaceutical industry to assess and minimize the potential of drug candidates to cause toxicity. At early stages of drug discovery, iteration between medicinal chemistry and drug metabolism can eliminate perceived reactive metabolite-mediated chemical liabilities without compromising pharmacological activity or the need for extensive safety evaluation beyond standard practices. In the future, reactive metabolite evaluation may also be useful during clinical development for improving clinical risk assessment and risk management. Currently, there remains a huge gap in our understanding of the basic mechanisms that underlie chemical stress-mediated adverse reactions in humans. This Review summarizes our views on this complex topic, and includes insights into practices considered by the pharmaceutical industry.

Mechanistic biomarkers provide early and sensitive detection of acetaminophen‐induced acute liver injury at first presentation to hospital

An adverse drug reaction is any undesirable effect of a drug beyond its anticipated therapeutic effects occurring during clinical use. In contrast, an adverse drug event is an untoward occurrence after exposure to a drug that is not necessarily caused by the drug.1 When a drug is marketed little is known about its safety in clinical use because only about 1500 patients are likely to have been exposed to it.1,2 Thus drug safety assessment should be considered an integral part of everyday clinical practice since detection and diagnosis often depend on clinical acumen. In this article we review the current status of adverse drug reactions, briefly describing the complexity of the more bizarre reactions and outlining a strategy to eliminate serious adverse drug reactions. Summary points Adverse drug reactions are a common clinical problem They are diagnosed on clinical grounds from the temporal relation between the start and finish of drug treatment and the onset and offset of the reaction Pharmacological adverse reactions are generally dose-dependent, related to the pharmacokinetic properties of the drug, and resolve when the dose is reduced Idiosyncratic adverse reactions are not related to the known pharmacology of the drug, do not show any simple dose-response relation, and resolve only when treatment is discontinued Vigilance by clinicians in detecting, diagnosing, and reporting adverse reactions is important for continued drug safety monitoring