Use of quantitative bias analysis to evaluate single-arm trials with real-world data external controls

PURPOSE

Use of real-world data (RWD) for external controls added to single-arm trials (SAT) is increasingly prevalent in regulatory submissions. Due to inherent differences in the data-generating mechanisms, biases can arise. This paper aims to illustrate how to use quantitative bias analysis (QBA).

METHODS

Advanced non-small cell lung cancer (NSCLC) serves as an example, where many small subsets of patients with molecular tumor subtypes exist. First, some sources of bias that may occur in oncology when comparing RWD to SAT are described. Second, using a hypothetical immunotherapy agent, a dataset is simulated based on expert input for survival analysis of advanced NSCLC. Finally, we illustrate the impact of three biases: missing confounder, misclassification of exposure, and outcome evaluation.

RESULTS

For each simulated scenario, bias was induced by removing or adding data; hazard ratios (HRs) were estimated applying conventional analyses. Estimating the bias-adjusted treatment effect and uncertainty required carefully selecting the bias model and bias factors. Although the magnitude of each biased and bias-adjusted HR appeared moderate in all three hypothetical scenarios, the direction of bias was variable.

CONCLUSION

These findings suggest that QBA can provide an intuitive framework for bias analysis, providing a key means of challenging assumptions about the evidence. However, the accuracy of bias analysis is itself dependent on correct specification of the bias model and bias factors. Ultimately, study design should reduce bias, but QBA allows us to evaluate the impact of unavoidable bias to assess the quality of the evidence.

Updated core competencies in pharmacoepidemiology to inform contemporary curricula and training for academia, government, and industry

PURPOSE

The first paper to specify the core content of pharmacoepidemiology as a profession was published by an ISPE (International Society for Pharmacoepidemiology) workgroup in 2012 (Jones JK et al. PDS 2012; 21[7]:677-689). Due to the broader and evolving scope of pharmacoepidemiology, ISPE considers it important to proactively identify, update and expand the list of core competencies to inform curricula of education programs; thus, better positioning pharmacoepidemiologists across academic, government (including regulatory), and industry positions. The aim of this project was to update the list of core competencies in pharmacoepidemiology.

METHODS

To ensure applicability of findings to multiple areas, a working group was established consisting of ISPE members with positions in academia, industry, government, and other settings. All competencies outlined by Jones et al. were extracted from the initial manuscript and presented to the working group for review. Expert-based judgments were collated and used to identify consensus. It was noted that some competencies could contribute to multiple groups and could be directly or indirectly related to a group.

RESULTS

Five core domains were proposed: (1) Epidemiology, (2) Clinical Pharmacology, (3) Regulatory Science, (4) Statistics and data science, and (5) Communication and other professional skills. In total, 55 individual competencies were proposed, of which 25 were new competencies. No competencies from the original work were dropped but aggregation or amendments were made where considered necessary.

CONCLUSIONS

While many core competencies in pharmacoepidemiology have remained the same over the past 10 years, there have also been several updates to reflect new and emerging concepts in the field.

Identification of cardiotoxicity related to non-small cell lung cancer (NSCLC) treatments: A systematic review

Introduction: In the last few decades, there has been a rapid development in cancer therapies and improved detection strategies, hence the death rates caused by cancer have decreased. However, it has been reported that cardiovascular disease has become the second leading cause of long-term morbidity and fatality among cancer survivors. Cardiotoxicity from anticancer drugs affects the heart's function and structure and can occur during any stage of the cancer treatments, which leads to the development of cardiovascular disease. Objectives: To investigate the association between anticancer drugs for non-small cell lung cancer (NSCLC) and cardiotoxicity as to whether: different classes of anticancer drugs demonstrate different cardiotoxicity potentials; different dosages of the same drug in initial treatment affect the degree of cardiotoxicity; and accumulated dosage and/or duration of treatments affect the degree of cardiotoxicity. Methods: This systematic review included studies involving patients over 18 years old with NSCLC and excluded studies in which patients' treatments involve radiotherapy only. Electronic databases and registers including Cochrane Library, National Cancer Institute (NCI) Database, PubMed, Scopus, Web of Science, ClinicalTrials.gov and the European Union Clinical Trials Register were systematically searched from the earliest available date up until November 2020. A full version protocol of this systematic review (CRD42020191760) had been published on PROSPERO. Results: A total of 1785 records were identified using specific search terms through the databases and registers; 74 eligible studies were included for data extraction. Based on data extracted from the included studies, anticancer drugs for NSCLC that are associated with cardiovascular events include bevacizumab, carboplatin, cisplatin, crizotinib, docetaxel, erlotinib, gemcitabine and paclitaxel. Hypertension was the most reported cardiotoxicity as 30 studies documented this cardiovascular adverse event. Other reported treatment-related cardiotoxicities include arrhythmias, atrial fibrillation, bradycardia, cardiac arrest, cardiac failure, coronary artery disease, heart failure, ischemia, left ventricular dysfunction, myocardial infarction, palpitations, and tachycardia. Conclusion: The findings of this systematic review have provided a better understanding of the possible association between cardiotoxicities and anticancer drugs for NSCLC. Whilst variation is observed across different drug classes, the lack of information available on cardiac monitoring can result in underestimation of this association. Systematic Review Registration: https://www.crd.york.ac.uk/prospero/display_record.php?ID=CRD42020191760, identifier PROSPERO CRD42020191760.

Impact of European Union Label Changes for Fluoroquinolone-Containing Medicinal Products for Systemic and Inhalation Use: Post-Referral Prescribing Trends

INTRODUCTION

Concerns of the persistence and severity of the adverse effects of fluoroquinolones, mainly involving the nervous system, muscles and joints, resulted in the 2018 referral procedure led by the European Medicines Agency (EMA). They advised to stop prescribing fluoroquinolones for infections of mild severity or of a presumed self-limiting course and for prevention of infections, plus to restrict prescriptions in cases of milder infections where other treatment options are available, and restrict in at-risk populations. We aimed to examine whether the impact of EMA regulatory interventions implemented throughout 2018-2019 had an impact on fluoroquinolone prescribing rates.

METHODS

A retrospective population-based cohort study was conducted using electronic health care records from six European countries between 2016 and 2021. We analysed monthly incident fluoroquinolone use rates overall and for each fluoroquinolone active substance through flexible modelling via segmented regression to detect time points of trend changes, in monthly percentage change (MPC).

RESULTS

The incidence of fluoroquinolone use ranged from 0.7 to 8.0/1000 persons per month over all calendar years. While changes in fluoroquinolone prescriptions were observed over time across countries, these were inconsistent and did not seem to be temporally related to EMA interventions (e.g., Belgium: February/May 2018, MPC - 33.3%, 95% confidence interval [CI] - 35.9 to - 30.7; Germany: February/May 2019, MPC - 12.6%, 95% CI - 13.7 to - 11.6]; UK: January/April 2016, MPC - 4.9%, 95% CI - 6.2 to - 3.6).

CONCLUSION

The regulatory action associated with the 2018 referral did not seem to have relevant effects on fluoroquinolone prescribing in primary care.

A Landscape Analysis of Post-Marketing Studies Registered in the EU PAS Register and ClinicalTrials.gov Focusing on Pregnancy Outcomes or Breastfeeding Effects: A Contribution from the ConcePTION Project

Introduction

A large proportion of medicine product labels lack information on safety in pregnancy and breastfeeding. To address this gap, pharmaceutical companies are requested to develop post-approval studies regarding the use of drugs by pregnant and breastfeeding women.

Objective

Our study aims to review key features of observational studies in pregnancy and breastfeeding and their impact on the respective medicine product labels.

Methods

Observational studies focusing on the safety evaluation of medicines used during pregnancy and breastfeeding were selected from the European Union Register of Post-Authorization Studies (EU PAS register) and ClinicalTrials.gov. We extracted information on the variables of interest and performed an impact assessment on the respective label.

Results

A total of 141 observational studies were eligible. Of these, 63 studies (45%) were based on primary data collection and 55 studies (39%) on secondary use of health data. A small number of studies (8%) aimed to evaluate drug safety during breastfeeding. Studies using secondary data collection lasted around 2.9 years as opposed to 7.5 years’ duration for studies using primary data collection. Only two product labels were updated based on the study results.

Conclusion

The duration is significantly longer for studies based on primary data collection, and these are also smaller in size (less power), whereas outcomes of interest are similar. For completed studies, the impact on the label was very low. Given the gap in adequate pregnancy information on product labels, the current process of generating evidence in pregnancy and breastfeeding seems neither efficient nor impactful. To support evidence-based decision making by prescribers, this current process might be redesigned.

Supplementary Information

The online version contains supplementary material available at 10.1007/s40264-022-01154-7.

Overview of the EU PAS register post-authorization studies performed in Europe from September 2010 to December 2018

BACKGROUND

The European post-authorisation study (EU PAS) register is a repository launched in 2010 by the European Medicines Agency (EMA). All EMA-requested PAS, commonly observational studies, must be recorded in this register. Multi-database studies (MDS) leveraging secondary data have become an important strategy to conduct PAS in recent years, as reflected by the type of studies registered in the EU PAS register.

OBJECTIVES

To analyse and describe PAS in the EU PAS register, with focus on MDS.

METHODS

Studies in the EU PAS register from inception to 31^st December 2018 were described concerning transparency, regulatory obligations, scope, study type (e.g. observational study, clinical trial, survey, systematic review/meta-analysis), study design, type of data collection and target population. MDS were defined as studies conducted through secondary use of >1 data source not linked at patient-level. Data extraction was carried out independently by 14 centres with expertise in pharmacoepidemiology, using publicly available information in the EU PAS register including study protocol, whenever available, using a standardised data collection form. For validation purposes, a second revision of key fields for a 15% random sample of studies was carried out by a different centre. The inter-rater reliability (IRR) was then calculated. Finally, to identify predictors of primary data collection-based studies /vs those based on secondary use of healthcare databases) or MDS (vs. non-MDS), odds ratios (OR) and 95% confidence intervals (CI) were calculated fitting univariate logistic regression models.

RESULTS

Overall, 1,426 studies were identified. Clinical trials (N=30; 2%), systematic reviews/meta-analyses (N=16; 1%) and miscellaneous study designs (N=46; 3%) were much less common than observational studies (N=1,227; 86%). The protocol was available for 63% (N=360) of 572 observational studies requested by a competent authority. Overall, 36% (N=446) of observational studies were based fully or partially on primary data collection. Of 757 observational studies based on secondary use of data alone, 282 (37%) were MDS. Drug utilisation was significantly more common as a study scope in MDS compared to non-MDS studies. The overall percentage agreement among collaborating centres that collected the data concerning study variables was highest for study type (93.5%) and lowest for type of secondary data (67.8%).

CONCLUSIONS

Observational studies were the most common type of studies in the EU PAS register, but 30% used primary data, which is more resource-intensive. Almost half of observational studies using secondary data were MDS. Data recording in the EU PAS register may be improved further, including more widespread availability of study protocols to improve transparency.

A Framework for Methodological Choice and Evidence Assessment for Studies Using External Comparators from Real-World Data

Several approaches have been proposed recently to accelerate the pathway from drug discovery to patient access. These include novel designs such as using controls external to the clinical trial where standard randomised controls are not feasible. In parallel, there has been rapid growth in the application of routinely collected healthcare ‘real-world’ data for post-market safety and effectiveness studies. Thus, using real-world data to establish an external comparator arm in clinical trials is a natural next step. Regulatory authorities have begun to endorse the use of external comparators in certain circumstances, with some positive outcomes for new drug approvals. Given the potential to introduce bias associated with observational studies, there is a need for recommendations on how external comparators should be best used. In this article, we propose an evaluation framework for real-world data external comparator studies that enables full assessment of available evidence and related bias. We define the principle of exchangeability and discuss the applicability of criteria described by Pocock for consideration of the exchangeability of the external and trial populations. We explore how trial designs using real-world data external comparators fit within the evidence hierarchy and propose a four-step process for good conduct of external comparator studies. This process is intended to maximise the quality of evidence based on careful study design and the combination of covariate balancing, bias analysis and combining outcomes.

Determination of Cry9C Protein in Corn-Based Foods by Enzyme-Linked Immunosorbent Assay: Interlaboratory Study

The performance of a commercially available enzyme-linked immunosorbent assay kit (Enviro-Logix) was assessed for the determination of Cry9C protein, which is produced by the genetically modified corn StarLink, in 8 types of corn-based foods (starch, refined oil, soft tortillas, tortilla chips, corn flakes, corn puffs, corn muffins, and corn bread) in an interlaboratory study involving 7 laboratories in the United States. The assay kit is a double antibody sandwich and is based on the specific interaction between antibody and antigen. The Cry9C protein analyte is sandwiched between 2 antibodies, one to capture the analyte and the other is conjugated to the enzyme, horseradish peroxidase. The enzyme uses tetramethylbenzidine/peroxide for color development. A strong acid stopping reagent is then used to change the color from blue to a stable yellow. The intensity of the color is proportional to the concentration of the Cry9C protein. In this study blind duplicates of control samples (blank material prepared from non- StarLink corn), spiked samples (blank material with the addition of Cry9C protein), and samples containing incurred analyte (products prepared with StarLink corn) were analyzed. Cry9C protein from 2 different sources was used to spike the food products. Cry9C protein produced and purified from a bacterial host was used to prepare spiked test samples at 2.72 and 6.8 ng/g. Cry9C protein from StarLink corn flour was used to prepare spiked samples at 1.97 ng/g. Average recoveries for samples spiked with corn flour Cry9C protein at 1.97 ng/g ranged from 73 to 122%, within-laboratory relative standard deviations (RSDr) ranged from 6 to 22%, and between-laboratories relative standard deviations (RSDR) ranged from 16 to 56%. Average recoveries for samples spiked with bacterial Cry9C protein at 2.72 and 6.8 ng/g ranged from 27 to 96% and from 32 to 113%, respectively; RSDr values ranged from 10 to 35%and from 7 to 38%, respectively; and the RSDR ranged from 28 to 84%and 15 to 75%, respectively. The incurred test samples were found to contain Cry9C protein at levels ranging from 0.8 to 3187 ng/g depending on the product, RSDr values ranged from 5 to 16% and RSDR values ranged from 11 to 71%. Results of the statistical analysis indicate that this method is applicable to the determination of Cry9C protein in the 8 types of collaboratively studied corn-based products containing Cry9C protein (from StarLink ) at levels of ≥2 ng/g.

Beam Energy and Centrality Dependence of Direct-Photon Emission from Ultrarelativistic Heavy-Ion Collisions

The PHENIX collaboration presents first measurements of low-momentum (0.4<p_{T}<3  GeV/c) direct-photon yields from Au+Au collisions at sqrt[s_{NN}]=39 and 62.4 GeV. For both beam energies the direct-photon yields are substantially enhanced with respect to expectations from prompt processes, similar to the yields observed in Au+Au collisions at sqrt[s_{NN}]=200. Analyzing the photon yield as a function of the experimental observable dN_{ch}/dη reveals that the low-momentum (>1  GeV/c) direct-photon yield dN_{γ}^{dir}/dη is a smooth function of dN_{ch}/dη and can be well described as proportional to (dN_{ch}/dη)^{α} with α≈1.25. This scaling behavior holds for a wide range of beam energies at the Relativistic Heavy Ion Collider and the Large Hadron Collider, for centrality selected samples, as well as for different A+A collision systems. At a given beam energy, the scaling also holds for high p_{T} (>5  GeV/c), but when results from different collision energies are compared, an additional sqrt[s_{NN}]-dependent multiplicative factor is needed to describe the integrated-direct-photon yield.

Utilisation and Safety of Deferasirox: Results from an Observational Cohort Study in England

INTRODUCTION

Deferasirox (EXJADE^®, Novartis, UK) is an oral iron-chelating agent primarily used to reduce chronic iron overload in patients receiving blood transfusions for various chronic anaemias and some non-transfusion dependant anaemias.

OBJECTIVE

The aim of this study was to examine the utilisation and safety of deferasirox used in general practice in England.

METHOD

A single exposure observational cohort study design was used. Patients were identified from dispensed prescriptions for deferasirox between September 2006 and September 2014. Outcome data were collected via postal questionnaires sent to prescribers ≥ 6 months after first dispensed prescription for an individual patient. Summary descriptive statistics were calculated.

RESULTS

The evaluable cohort consisted of 122 patients, of which 41.8% were aged 2-17 years. Frequent reasons for prescribing were sickle cell anaemia (27/103 where specified, 26.2%) and beta thalassaemia (26, 25.2%). The majority of patients (43/51, 84.3%) were prescribed the licensed doses of 10 or 20 mg/kg/day at start. Prior measurements of serum creatinine were only reported for a small proportion this study (18/122, 14.8%). In total, 91 incident events were reported, including two of raised serum creatinine.

CONCLUSION

These results show that deferasirox is largely being prescribed for its licensed indications in general practice in England and events reported were consistent with the known safety profile.

Drugs and life-threatening ventricular arrhythmia risk: results from the DARE study cohort

OBJECTIVES

To establish a unique sample of proarrhythmia cases, determine the characteristics of cases and estimate the contribution of individual drugs to the incidence of proarrhythmia within these cases.

SETTING

Suspected proarrhythmia cases were referred by cardiologists across England between 2003 and 2011. Information on demography, symptoms, prior medical and drug histories and data from hospital notes were collected.

PARTICIPANTS

Two expert cardiologists reviewed data for 293 referred cases: 130 were included. Inclusion criteria were new onset or exacerbation of pre-existing ventricular arrhythmias, QTc >500 ms, QTc >450 ms (men) or >470 ms (women) with cardiac syncope, all secondary to drug administration. Exclusion criteria were acute ischaemia and ischaemic polymorphic ventricular tachycardia at presentation, structural heart disease, consent withdrawn or deceased prior to study. Descriptive analysis of Caucasian cases (95% of included cases, n=124) and culpable drug exposures was performed.

RESULTS

Of the 124 Caucasian cases, 95 (77%) were QTc interval prolongation-related; mean age was 62 years (SD 15), and 63% were female. Cardiovascular comorbidities included hypertension (53%) and patient-reported 'heart rhythm problems' (73%). Family history of sudden death (36%) and hypokalaemia at presentation (27%) were common. 165 culpable drug exposures were reported, including antiarrhythmics (42%), of which amiodarone and flecainide were the most common. Sotalol, a beta-blocking agent with antiarrhythmic activity, was also common (15%). 26% reported multiple drugs, of which 84% reported at least one cytochrome (CYP) P450 inhibitor. Potential pharmacodynamics interactions identified were mainly QT prolongation (59%).

CONCLUSIONS

Antiarrhythmics, non-cardiac drugs and drug combinations were found to be culpable in a large cohort of 124 clinically validated proarrhythmia cases. Potential clinical factors that may warn the prescriber of potential proarrhythmia include older women, underlying cardiovascular comorbidity, family history of sudden death and hypokalaemia.

Safety of Atrovent® CFC-free inhaler: respiratory events reported from an observational cohort study in England

OBJECTIVES

The aim of the study was to identify any unexpected clinical events associated with starting the new CFC-free formulation of Atrovent^® MDI in general practice in England.

METHODS

An active surveillance cohort study was conducted with a focus on selected clinical events, including respiratory symptoms, in past users of Atrovent^® CFC MDI ('switchers') and Atrovent^® naïve users. Incidence density rate ratios (with 99% confidence intervals) for events occurring in the first 3 months of exposure (risk period-ID_1-3 ) compared to 3 months prior to starting treatment (reference period-ID_R ) were calculated.

RESULTS

The cohort consisted of 13 211 patients (median age 70 years, 50.1% female; 63.5% prior users of Atrovent^® CFC MDI ('switchers')). Common respiratory events occurred at higher rates after starting treatment than before for switchers, for example lower respiratory tract infection (LRTI) [ID₁ /ID_R = 1.45 (99% CI: 1.17, 1.81)] and worsening asthma [ID₁ /ID_R = 1.58 (99% CI: 1.00, 2.51)]. Of these events only LRTI was significant for Atrovent^® naïve patients [ID₁ /ID_R = 1.42 (99% CI: 1.04, 1.95)].

CONCLUSIONS

The results of this study suggest effect modification of risk as a result of prior Atrovent^® CFC MDI use. Overall, Atrovent^® CFC-free MDI appeared to be reasonably well tolerated in the immediate postmarketing period and the safety profile appeared similar to that of the CFC formulation.

Use of atomoxetine and suicidal ideation in children and adolescents: Results of an observational cohort study within general practice in England

AIM

To investigate the association between atomoxetine, a drug used in the treatment of Attention Deficit Hyperactivity Disorder (ADHD), and suicidal ideation, within a cohort of 2-18-year-old patients in England.

METHODS

The study was conducted using the observational cohort technique of Modified prescription event monitoring (M-PEM). Patients prescribed atomoxetine were identified from dispensed prescriptions issued by primary care physicians. A customised postal GP questionnaire was used to capture outcome data for suicidal ideation. A matched pair cohort analysis was performed within patients to compare the risk of suicidal ideation in the period after starting atomoxetine with the risk prior to starting atomoxetine; this was stratified by age and concomitant use of methylphenidate. Additional information on patient characteristics, and events of interest was also collected; individual cases of suicidal ideation were qualitatively assessed for drug relatedness.

RESULTS

Of the final cohort (n=4509); 85.5% male (n=3857), median age 11 years (IQR: 9,14). Primary prescribing indication for atomoxetine was ADHD (n=4261, 94.6%). Almost a quarter of the cohort had been co-prescribed methylphenidate. Results of the matched pair cohort analysis indicated that the period after starting atomoxetine was not associated with an increase in the incidence of suicidal ideation compared to the period prior to starting treatment (RR: 0.71; CI: 0.48-1.07; P-value: 0.104). Individual case assessment of suicidal ideation suggested a causal association within a number of cases.

CONCLUSIONS

This study found no evidence of an increased risk of suicidal ideation during treatment with atomoxetine, compared to the period prior to starting treatment. Amongst age specific subgroups, this risk may change. Nonetheless, individual case assessment suggested a causal relationship in some patients, hence physicians need to be aware of the possibility of developing this event, and furthermore consider how best to detect it in this paediatric population. This study demonstrates the importance of combining quantitative statistical analyses with a qualitative case series assessment.

Safety of Intranasal Quadrivalent Live Attenuated Influenza Vaccine (QLAIV) in Children and Adolescents: A Pilot Prospective Cohort Study in England

Introduction

Fluenz Tetra is an intranasal quadrivalent live attenuated influenza vaccine (QLAIV) and is recommended as the vaccine of choice for children in the 2014/2015 influenza season vaccination programme in the UK.

Objective

The primary objective of the study was to estimate the crude incidence rate of adverse events of interest (AEIs) following vaccination with the nasal QLAIV early in the 2014/2015 influenza season in children and adolescents in England.

Methods

A pilot non-interventional cohort post-authorisation safety study (PASS) was conducted during the 2014/2015 influenza season in England. Vaccinees were recruited via the mass vaccination programme in England. Participant outcomes, validated by a healthcare professional (general practitioner) where appropriate, were captured through questionnaires (surface mail, telephone, e-questionnaire). Data analysis comprised descriptive statistics and calculation of event risks and incidence rates, stratified by age group and selected co-morbidities.

Results

The final evaluable cohort consisted of 385 participants; the median (interquartile range) age was 4 (3–9) years with a range of 2–17 years, and 53.2 % were female. The most frequently reported AEI was nasal congestion (n = 167; 43.4 %; 312.3 per 1000 patient-weeks [95 % CI 267.3–364.8]). Further frequently reported AEIs were malaise (n = 87; 22.6 %; 123.4 per 1000 patient-weeks [95 % CI 98.9–154.1]) and cough (n = 80; 20.8 %; 118.5 per 1000 patient-weeks [95 % CI 95.1–147.8]). Five hypersensitivity-type reactions were reported, although on follow-up none were true hypersensitivity reactions or required hospitalisation. No serious adverse events (SAEs) were reported, with no hospitalisations or deaths. No significant change in reactogenicity or other apparent safety signals was detected as part of this study.

Conclusion

The pilot study showed no significant change in reactogenicity or other apparent safety signals from the data collected. Continued enhanced surveillance of seasonal influenza vaccines will ensure their ongoing safety for the prevention of serious illness from seasonal influenza outbreaks.

Electronic supplementary material

The online version of this article (doi:10.1007/s40264-015-0384-7) contains supplementary material, which is available to authorized users.

Utilisation and Tolerability of Aliskiren in the Primary Care Setting in England

Aliskiren (Rasilez), a direct renin inhibitor, is indicated for the treatment of essential hypertension. A postmarketing prescription-event monitoring (PEM) study was conducted in England to monitor the safety and utilization of aliskiren. Summary statistics and event incidence densities were calculated. The cohort consisted of 6385 individuals with a median age of 68 years (interquartile range, 59-76). Aliskiren was largely prescribed for its licensed indication of hypertension (93.3%) and was reported as "effective" by the prescriber in 77.4% of individuals. Frequently reported clinical events during treatment were diarrhea (3.1% of on-treatment events), malaise/lassitude (3.0%), and nausea/vomiting (1.2%), which were also common reasons for treatment cessation. Renal events were rare, with 24 cases probably or possibly related to aliskiren use, and four of which were classified as acute renal failure using RIFLE (Risk Injury Failure Loss End-Stage Kidney Disease) criteria. These results should be used in conjunction with other clinical and pharmacoepidemiologic studies to optimize the safe prescribing of aliskiren.

Utilisation of extended release quetiapine (Seroquel XL™): Results from an observational cohort study in England

BACKGROUND

A post-authorisation safety study was carried out as part of the EU Risk Management Plan to examine the long-term (up to 12 months) use of quetiapine XL as prescribed in general practice in England.

AIM

To present a description of the drug utilisation characteristics of quetiapine XL.

METHODS

An observational, population-based cohort design using the technique of Modified Prescription-Event Monitoring (M-PEM). Patients were identified from dispensed prescriptions issued by general practitioners (GPs) for quetiapine XL between September 2008 and February 2013. Questionnaires were sent to GPs 12 months following the 1st prescription for each individual patient, requesting drug utilisation information. Cohort accrual was extended to recruit additional elderly patients (special population of interest). Summary descriptive statistics were calculated.

RESULTS

The final M-PEM cohort consisted of 13,276 patients; median age 43 years (IQR: 33, 55) and 59.0% females. Indications for prescribing included bipolar disorder (n=3820), MDD (n=2844), schizophrenia (n=2373) and other (non-licensed) indications (n=3750). Where specified, 59.3% (7869/13,276) were reported to have used quetiapine IR (immediate release formulation) previously at any time. The median start dose was highest for patients with schizophrenia (300 mg/day [IQR 150, 450]). The final elderly cohort consisted of 3127 patients and 28.5% had indications associated with dementia. The median start dose for elderly patients was highest for patients with schizophrenia or BD (both 100mg/day [IQR 50, 300]).

CONCLUSIONS

The prevalence of off-label prescribing in terms of indication and high doses was common, as was use in special populations such as the very elderly. Whilst off-label use may be unavoidable in certain situations, GPs may need to re-evaluate prescribing in circumstances where there may be safety concerns. This study demonstrates the ongoing importance of observational studies such as M-PEM to gather real-world clinical data to support the post-marketing benefit:risk management of new medications, or existing medications for which license extensions have been approved.

Measurements of Elliptic and Triangular Flow in High-Multiplicity 3He+Au Collisions at √(s(NN))=200 GeV

We present the first measurement of elliptic (v(2)) and triangular (v(3)) flow in high-multiplicity (3)He+Au collisions at √(s(NN))=200  GeV. Two-particle correlations, where the particles have a large separation in pseudorapidity, are compared in (3)He+Au and in p+p collisions and indicate that collective effects dominate the second and third Fourier components for the correlations observed in the (3)He+Au system. The collective behavior is quantified in terms of elliptic v(2) and triangular v(3) anisotropy coefficients measured with respect to their corresponding event planes. The v(2) values are comparable to those previously measured in d+Au collisions at the same nucleon-nucleon center-of-mass energy. Comparisons with various theoretical predictions are made, including to models where the hot spots created by the impact of the three (3)He nucleons on the Au nucleus expand hydrodynamically to generate the triangular flow. The agreement of these models with data may indicate the formation of low-viscosity quark-gluon plasma even in these small collision systems.

Indicators of drug-seeking aberrant behaviours: the feasibility of use in observational post-marketing cohort studies for risk management

Background

Problematic prescription drug use is reflected by or associated with drug-seeking aberrant behaviours. Research gaps include lack of post-marketing evidence and instruments. As part of the pharmacovigilance requirements, a risk management plan was developed for fentanyl buccal tablets (FEBT) by the manufacturer, with an additional pharmacovigilance activity requested by the regulatory authority, to investigate the risks of misuse, abuse, criminal use, off-label use and accidental exposure to FEBT after the product became commercially available. A Modified Prescription-Event Monitoring (M-PEM), observational, post-authorisation safety surveillance (PASS) study was conducted, with an overall aim to examine the use of FEBT in relation to their safety as prescribed in primary care in England. One of the exploratory objectives included estimating the prevalence of aberrant behaviours during FEBT treatment.

Objective

To determine the feasibility of estimating the prevalence of risk factors associated with dependence on starting treatment and aberrant behaviours in patients during treatment with a prototypical abuse liable substance (fentanyl), as based on the application of an existing index (the Chabal criteria).

Methods

Data were collected as part of the M-PEM PASS study; exposure and outcome data (including risk factors for dependence and aberrant behaviours based on behavioural not clinical manifestations) were derived from questionnaires sent to primary care physicians in England during April 2008 to June 2011. For the exploratory objective of interest, descriptive statistics and simple (non-weighted) risk scores were constructed on aggregate counts (score ≥3 considered ‘high-risk’). Supplementary analyses explored the relationship between the two indices and the characteristics of patients with aberrant behaviours and those without (crude odds ratios plus 95 % confidence interval (CI) were calculated).

Results

In a cohort of 551 patients, the prevalence of at least one pre-existing risk factor for dependence was 26 % (n = 145), whilst the frequency of aberrant behaviours observed during treatment was 8 % (n = 46). Patients with aberrant behaviours had several different characteristics to patients without. The two indices were associated (χ² df (20) = 58.72, p < 0.001), but a high-dependence risk-factor score provided a poor indication of high aberrant behaviour risk; the area under the receiver operating characteristic curve was 0.58 (95 % CI 0.41, 0.74).

Limitations

Study limitations included subjectivity in relation to physicians identifying aberrant behaviours, and under-reporting thereof in PASS observational study designs. The presence of these criteria does not confirm misuse, but should be considered as a signal of problematic opioid misuse, which requires investigation. Further research is needed to develop a more robust analytical construct.

Conclusion

In this PASS study, the prevalence of at least one pre-existing risk factor for dependence was 26 %, whilst the frequency of aberrant behaviours observed during treatment was 8 %. Patients with aberrant behaviours had several different characteristics to patients without. This study demonstrates the feasibility of the systematic collection of physician reports of risk factors for dependence and aberrant behaviours to facilitate the development of risk scores, using these reports to support the post-marketing risk management of products with misuse potential.

Specialist Cohort Event Monitoring studies: a new study method for risk management in pharmacovigilance

The evolving regulatory landscape has heightened the need for innovative, proactive, efficient and more meaningful solutions for 'real-world' post-authorization safety studies (PASS) that not only align with risk management objectives to gather additional safety monitoring information or assess a pattern of drug utilization, but also satisfy key regulatory requirements for marketing authorization holder risk management planning and execution needs. There is a need for data capture across the primary care and secondary care interface, or for exploring use of new medicines in secondary care to support conducting PASS. To fulfil this need, event monitoring has evolved. The Specialist Cohort Event Monitoring (SCEM) study is a new application that enables a cohort of patients prescribed a medicine in the hospital and secondary care settings to be monitored. The method also permits the inclusion of a comparator cohort of patients receiving standard care, or another counterfactual comparator group, to be monitored concurrently, depending on the study question. The approach has been developed in parallel with the new legislative requirement for pharmaceutical companies to undertake a risk management plan as part of post-authorization safety monitoring. SCEM studies recognize that the study population comprises those patients who may have treatment initiated under the care of specialist health care professionals and who are more complex in terms of underlying disease, co-morbidities and concomitant medications than the general disease population treated in primary care. The aims of this paper are to discuss the SCEM new-user study design, rationale and features that aim to address possible bias (such as selection bias) and current applications.

Establishment of transplantation tolerance via minimal conditioning in aged recipients

Mixed hematopoietic chimerism is a powerful means of generating donor-specific tolerance, allowing long-term graft acceptance without lifelong dependence on immunosuppressive drugs. To avoid the need for whole body irradiation and associated side effects, we utilized a radiation-free minimal conditioning regime to induce long-term tolerance across major histocompatibility barriers. We found that low-dose busulfan, in combination with host T cell depletion and short-term sirolimus-based immunosuppression, facilitated efficient donor engraftment. Tolerance was achieved when mice were transplanted with whole or T cell-depleted bone marrow, or purified progenitor cells. Tolerance induction was associated with an expansion in regulatory T cells and was not abrogated in the absence of a thymus, suggesting a dominant or compensatory peripheral mode of tolerance. Importantly, we were able to generate durable chimerism and tolerance to donor skin grafts in both young and aged mice, despite age-related thymic atrophy and immune senescence. Clinically, this is especially relevant as the majority of transplant recipients are older patients whose immune recovery might be dangerously slow and would benefit from radiation-free minimal conditioning regimes that allow efficient donor engraftment without fully ablating the recipient immune system.

Implications of off-label use: An example from the final results of an observational cohort study on Intrinsa® (testosterone patch)

INTRODUCTION

Off-label use is where a medicinal product is used for a medical purpose not in accordance with the authorised product information. Intrinsa® is a transdermal testosterone patch, which is indicated for use in hypoactive sexual desire disorder in bilaterally oophorectomised and hysterectomised women receiving concomitant estrogen therapy.

OBJECTIVES

To describe the utilization characteristics of patients prescribed testosterone patch (Intrinsa®) and to assess, where possible, if the product is being used according to the authorised product information.

STUDY DESIGN

Patients identified from dispensed prescriptions issued by general practitioners for Intrinsa® between March 2007 and August 2010. Postal questionnaires were sent to general practitioners six months following the date of the first prescription for Intrinsa® for each patient, requesting information including patient demographics and drug utilization.

MAIN OUTCOME MEASURES

Menopausal status and use of concomitant estrogen therapy.

RESULTS

The final cohort consisted of 3073 patients; the majority were females (3017, 98.2%). The most commonly reported indication was hypoactive sexual desire disorder in 2324 female patients (77.0%). Only 43.5% female patients (n = 1313) were reported to have been hysterectomised and bilaterally oophorectomised. For 1029 (34.1%) female patients there was no evidence that the patient was using concomitant estrogen therapy. Overall, only 643 patients (20.9%) in the cohort were being prescribed Intrinsa® according to the manufacturer's recommendations.

CONCLUSIONS

Evidence obtained solely from clinical trials might not be generalisable where off-label prescribing occurs in real-life, so evidence from post-marketing observational studies is important to provide complimentary data on a product's safety and effectiveness.

Neuropsychiatric events with varenicline: a modified prescription-event monitoring study in general practice in England

BACKGROUND

Varenicline (Champix(®)), launched in the UK in December 2006, is indicated for the treatment of smoking cessation in adults (≥18 years of age). In 2008, the Medicines and Healthcare products Regulatory Agency (MHRA) in the UK issued a warning suggesting that varenicline was associated with disparate neuropsychiatric symptoms, including depression, suicidal thoughts and behaviour. In response to this regulatory warning, the Drug Safety Research Unit conducted a modified prescription-event monitoring (M-PEM) study to monitor the safety of varenicline.

OBJECTIVE

The aim of this study was to estimate the incidence and examine the pattern of neuropsychiatric events reported to general practitioners (GPs) in England during the immediate postmarketing period for varenicline.

METHODS

A postmarketing surveillance study was conducted using the observational cohort technique of M-PEM. Patients were identified from dispensed prescriptions issued by primary care physicians between December 2006 and March 2007. Data on exposure, previous history of psychiatric illness and events reported during and after treatment were collected from questionnaires. In order to determine whether hazards for neuropsychiatric events of interest (depression, anxiety, aggression, suicidal ideation, non-fatal self-harm) were non-constant over time (which could indicate a possible association with the drug), the pattern of events was examined by plotting the smoothed hazard function estimate and then fitting a Weibull model. The Weibull model shape parameter (β) and 95 % confidence interval were used as a test for a non-constant hazard function (where a value of 1 indicates a constant hazard over time). In addition to this analysis, the difference in incidence densities (IDs) between month 1 and months 2-3 were calculated and compared.

RESULTS

The cohort comprised of 12,159 patients (median age 47 years [interquartile range 19]; 56.9 % [n = 6924 female]). The number of events reported during treatment, reason for stopping, adverse drug reactions (ADRs), and the p-value for the Weibull shape parameter were as follows: depression (n = 94; 42; 19; p = 0.144); anxiety (n = 94; 49; 9; p = 0.009); aggression (n = 7; 4; 2; p = 0.465); suicidal ideation (n = 8; 4; 1; p = 0.989) and non-fatal self-harm (n = 5; 1; 0; p = 0.771). No differences in the IDs between months 1 and months 2-3 were found for any of the events.

CONCLUSION

Whilst between 7 and 17 % of neuropsychiatric events were attributed to the drug by GPs and approximately 20-50 % were given as reasons for stopping, no signal was raised using the ID differences approach, and only anxiety was flagged as a potential signal for an ADR using the Weibull model. The signal for anxiety requires further evaluation to determine whether the drug plays a part in the development of anxiety or whether it is a withdrawal symptom caused by smoking cessation. Analysis methods will lack power when the numbers of events are low even when a large number of participants are included in the study.

Medium modification of jet fragmentation in Au+Au collisions at √[s(NN)]=200 GeV measured in direct photon-hadron correlations

The jet fragmentation function is measured with direct photon-hadron correlations in p+p and Au+Au collisions at √[s(NN)]=200 GeV. The p(T) of the photon is an excellent approximation to the initial p(T) of the jet and the ratio z(T)=p(T)(h)/p(T)(γ) is used as a proxy for the jet fragmentation function. A statistical subtraction is used to extract the direct photon-hadron yields in Au+Au collisions while a photon isolation cut is applied in p+p. I(AA), the ratio of hadron yield opposite the photon in Au+Au to that in p+p, indicates modification of the jet fragmentation function. Suppression, most likely due to energy loss in the medium, is seen at high z(T). The associated hadron yield at low z(T) is enhanced at large angles. Such a trend is expected from redistribution of the lost energy into increased production of low-momentum particles.

Influenza H1N1 (swine flu) vaccination: a safety surveillance feasibility study using self-reporting of serious adverse events and pregnancy outcomes

AIMS

During the global H1N1 influenza A (swine flu) pandemic 2009–2010, swine flu vaccines were expeditiously licensed and a mass vaccination programme for high risk groups, including pregnant women, was introduced in the UK. This pilot active safety surveillance study was performed to establish the feasibility of rapidly monitoring the new swine flu vaccines in large patient numbers receiving or offered the vaccination under normal conditions of use within a short time frame.

METHODS

A cohort design with safety data capture through modern technologies was carried out in Scotland, UK during the winter swine flu vaccination programme 2009–2010 in individuals receiving or offered the swine flu vaccination. The main outcome measures were self-reported serious adverse events (SAEs) and pregnancy outcomes.

RESULTS

The cohort comprised 4066 people; 3754 vaccinated and 312 offered the vaccination but not vaccinated. There were 939 self-reported events (838 different events), 53 judged to fit SAE criteria by the investigators, with nine judged as possibly, probably or definitely vaccine related. None of the seven deaths (six in vaccinees) were judged as vaccine related. One hundred and twenty-eight women reported 130 pregnancies during the study with 117 pregnant at study start. There were reports of four miscarriages in three women and six possible congenital abnormalities in live births.

CONCLUSIONS

Overall, no significant safety issues were identified. The methodology and use of modern technologies to collect safety data from large numbers of patients was successful and could be used again in similar safety studies.

Modified prescription-event monitoring studies: a tool for pharmacovigilance and risk management

Prescription-Event Monitoring (PEM) is a well established postmarketing surveillance technique designed to monitor the overall safety of newly marketed medicines as used in real-life clinical practice, usually in cohorts of at least 10 000 patients. At the Drug Safety Research Unit in the UK we are now moving towards a more targeted safety surveillance known as Modified PEM (M-PEM). These studies combine the advantages of conventional PEM studies (in monitoring general safety and identification of unexpected risks of a medicine) with that of a more targeted safety study that addresses specific questions (to better understand known or partially known risks with a medicine). Through the use of enhanced data collection questionnaires, M-PEM expands the range of applications of conventional PEM, which include more detailed characterization of real-life drug use, adherence to prescribing recommendations and targeted analysis of events requiring special monitoring by regulatory authorities. A particularly useful application is the evaluation of the safety of a medicine in special populations or subgroups (e.g. patients switching from another therapy or patients with a particular risk factor) or following important changes in the product's lifecycle (e.g. a licensing or formulation change). M-PEM studies therefore have an important contribution to make to pharmacovigilance and the risk management of medicines by providing valuable information on the use of new medications under real-life situations.

Cold nuclear matter effects on J/ψ yields as a function of rapidity and nuclear geometry in d+A collisions at sqrt[s(NN)]=200 GeV

We present measurements of J/ψ yields in d+Au collisions at sqrt[s(NN)]=200  GeV recorded by the PHENIX experiment and compare them with yields in p+p collisions at the same energy per nucleon-nucleon collision. The measurements cover a large kinematic range in J/ψ rapidity (-2.2<y<2.4) with high statistical precision and are compared with two theoretical models: one with nuclear shadowing combined with final state breakup and one with coherent gluon saturation effects. In order to remove model dependent systematic uncertainties we also compare the data to a simple geometric model. The forward rapidity data are inconsistent with nuclear modifications that are linear or exponential in the density weighted longitudinal thickness, such as those from the final state breakup of the bound state.

Signal generation in prescription event monitoring: investigation of a possible signal of colitis during rofecoxib treatment

Focal points

Comparison of gastrointestinal events reported for rofecoxib and meloxicam using prescription-event monitoring data in England

Focal points

Safety profile of rofecoxib as used in general practice in England: results of a prescription-event monitoring study

Focal points

Incidence of venous thromboembolism in users of strontium ranelate: an analysis of data from a prescription-event monitoring study in England

BACKGROUND

Strontium ranelate is indicated for the treatment of postmenopausal osteoporosis. An association between strontium ranelate and venous thromboembolism (VTE) was identified in an analysis of phase III clinical trials.

OBJECTIVE

To estimate the incidence of VTE in patients within the strontium ranelate (Protelos(R)) Prescription-Event Monitoring (PEM) study cohort during the first 12 months after starting treatment.

METHODS

Patients in this analysis were identified from dispensed prescriptions that had been issued by general practitioners (GPs) in England for strontium ranelate between October 2004 and January 2008. For each individual patient, a Green Form questionnaire was sent to their GP 12 months after the date of the first prescription issued for strontium ranelate, requesting information about the patient including start and stop dates of treatment (if stopped), age, sex, indication, any history of VTE events, reasons for stopping and whether the patient had any events since starting the drug. VTE was defined as reports of deep vein thrombosis (DVT) or pulmonary embolism (PE). The crude incidence of VTE was calculated for events that occurred during the first 12 months after starting treatment (plus 30 days after stopping), with 95% Poisson exact CIs for the whole cohort, and subsets defined by age and past history of VTE.

RESULTS

The final analysis cohort consisted of 10 782 patients. Where specified, mean age was 73.3 years (SD 11.45) [n = 10 696]; 9833 (91.3%) were female and 934 (8.7%) were male. Where the history of VTE was specified, 233 patients (2.6%) had a history of VTE prior to starting. In the first 12-month period, there were 48 incident reports of VTE (DVT or PE) during treatment (or within 30 days of stopping) in the cohort, with 7696.89 years of exposure, giving a crude incidence rate of VTE of 6.24 cases (95% CI 4.60, 8.27) per 1000 patient-years exposed.

CONCLUSIONS

This analysis has provided an estimate of the incidence of VTE in patients treated with strontium ranelate in the general practice setting. The rate is similar to estimates in populations of similar age and corresponds to the incidence found in patients from phase III clinical studies and observational cohort studies of strontium ranelate on this topic. The crude annual incidence rate of VTE in the PEM cohort is higher than the background annual incidence rate found in the UK population, but is similar to estimates in populations of similar age and populations receiving treatment for postmenopausal osteoporosis. Also, we acknowledge the potential for underestimating the incidence in this population. Nevertheless, this analysis contributes to the ongoing postmarketing safety assessment of this product.

Transition in yield and azimuthal shape modification in dihadron correlations in relativistic heavy ion collisions

Hard-scattered parton probes produced in collisions of large nuclei indicate large partonic energy loss, possibly with collective produced-medium response to the lost energy. We present measurements of π^{0} trigger particles at transverse momenta p{T}{t}=4-12  GeV/c and associated charged hadrons (p{T}{a}=0.5-7  GeV/c) vs relative azimuthal angle Δϕ in Au+Au and p+p collisions at sqrt[s{NN}]=200  GeV. The Au+Au distribution at low p{T}{a}, whose shape has been interpreted as a medium effect, is modified for p{T}{t}<7  GeV/c. At higher p{T}{t}, the data are consistent with unmodified or very weakly modified shapes, even for the lowest measured p{T}{a}, which quantitatively challenges some medium response models. The associated yield of hadrons opposing the trigger particle in Au+Au relative to p+p (I{AA}) is suppressed at high p{T} (I{AA}≈0.35-0.5), but less than for inclusive suppression (R{AA}≈0.2).

Measurement of bottom versus charm as a function of transverse momentum with electron-hadron correlations in p + p collisions at square root of s = 200 GeV

The momentum distribution of electrons from semileptonic decays of charm and bottom quarks for midrapidity |y|<0.35 in p+p collisions at square root of s=200 GeV is measured by the PHENIX experiment at the Relativistic Heavy Ion Collider over the transverse momentum range 2<pT<7 GeV/c. The ratio of the yield of electrons from bottom to that from charm is presented. The ratio is determined using partial D/D-->e(+/-)K(-/+)X (K unidentified) reconstruction. It is found that the yield of electrons from bottom becomes significant above 4 GeV/c in pT. A fixed-order-plus-next-to-leading-log perturbative quantum chromodynamics calculation agrees with the data within the theoretical and experimental uncertainties. The extracted total bottom production cross section at this energy is sigma(bb)=3.2(-1.1)(+1.2)(stat)(-1.3)(+1.4)(syst)mub.

Gluon-spin contribution to the proton spin from the double-helicity asymmetry in inclusive pi0 production in polarized p+p collisions at [sqrt]s=200 GeV

The double helicity asymmetry in neutral pion production for pT=1 to 12 GeV/c was measured with the PHENIX experiment to access the gluon-spin contribution, DeltaG, to the proton spin. Measured asymmetries are consistent with zero, and at a theory scale of micro2=4 GeV2 a next to leading order QCD analysis gives DeltaG[0.02,0.3]=0.2, with a constraint of -0.7<DeltaG[0.02,0.3]<0.5 at Deltachi2=9 (approximately 3sigma) for the sampled gluon momentum fraction (x) range, 0.02 to 0.3. The results are obtained using predictions for the measured asymmetries generated from four representative fits to polarized deep inelastic scattering data. We also consider the dependence of the DeltaG constraint on the choice of the theoretical scale, a dominant uncertainty in these predictions.

Onset of pi(0) suppression studied in Cu+Cu collisions at sqrt S NN=22.4, 62.4, and 200 GeV

Neutral pion transverse momentum (p(T)) spectra at midrapidity (|y| less than or approximately 0.35) were measured in Cu+Cu collisions at sqrt[s(NN)]=22.4, 62.4, and 200 GeV. Relative to pi_(0) yields in p+p collisions scaled by the number of inelastic nucleon-nucleon collisions (N(coll) the pi_(0) yields for p(T) more than or approximately 2 GeV/c in central Cu+Cu collisions are suppressed at 62.4 and 200 GeV whereas an enhancement is observed at 22.4 GeV. A comparison with a jet-quenching model suggests that final state parton energy loss dominates in central Cu+Cu collisions at 62.4 and 200 GeV, while the enhancement at 22.4 GeV is consistent with nuclear modifications in the initial state alone.

Prescriber adoption of newly approved selective COX-2 inhibitors

INTRODUCTION

There is no consistent definition of prescribers who adopt new drug treatments early. This study examines if COX-2 inhibitors (coxibs) were prescribed by subsets of practitioners and describes GP adoption patterns of coxibs and existing NSAIDs over time.

METHODS

A population-based drug utilisation study using a Dutch medication claims database. Prescribers of patients (18+yrs) prescribed an NSAID January 1999-December 2003 were identified. Four NSAID categories were chosen reflecting selectivity (coxibs, preferential COX-2 inhibitors and non-selective (ns) NSAIDs (sub-categorised as first or second line treatment)). The characteristics of prescribers issuing>10 prescriptions examined were: Type (GP, Specialist, Other); GP NSAID prescribing preference ratio (nsNSAIDs/coxib first prescription); coxib (ratio<3); prescriber proportion responsible for 100%, 80% and 50% of initiations. Odds Ratios (95%CI) were calculated (first-line nsNSAIDs as reference). Plots of prescribing proportions by quarter year were examined.

RESULTS

NSAID cohorts comprised: first-line ns (N=38783); second-line ns (N=1459); COX-2 preferential (N=3107); coxib (N=4202) patients. For all four cohorts, GPs were the most common prescriber type (>67%); the most frequent prescribing preference was for first-line nsNSAIDs; 50% percentile prescribing proportions were low (<9%). GPs were equally as likely to prescribe coxibs as first-line nsNSAIDs [OR 1.0 (0.9, 1.1)]. Plots of 100% prescriber proportion for first-line nsNSAIDs and coxibs showed convergence; 50th percentile prescriber proportions plots were constant.

CONCLUSIONS

Small subsets of prescribers accounted for the majority of initiations regardless of NSAID type. Further studies are needed on such prescribers to inform healthcare policies and encourage participation in post-marketing safety studies.