Saad A. W. Shakir

Under-reporting of adverse drug reactions : a systematic review.

The purpose of this review was to estimate the extent of under-reporting of adverse drug reactions (ADRs) to spontaneous reporting systems and to investigate whether there are differences between different types of ADRs. A systematic literature search was carried out to identify studies providing a numerical estimate of under-reporting. Studies were included regardless of the methodology used or the setting, e.g. hospital versus general practice. Estimates of under-reporting were either extracted directly from the published study or calculated from the study data. These were expressed as the percentage of ADRs detected from intensive data collection that were not reported to the relevant local, regional or national spontaneous reporting systems. The median under-reporting rate was calculated across all studies and within subcategories of studies using different methods or settings.In total, 37 studies using a wide variety of surveillance methods were identified from 12 countries. These generated 43 numerical estimates of under-reporting. The median under-reporting rate across the 37 studies was 94% (interquartile range 82–98%). There was no significant difference in the median under-reporting rates calculated for general practice and hospital-based studies. Five of the ten general practice studies provided evidence of a higher median under-reporting rate for all ADRs compared with more serious or severe ADRs (95% and 80%, respectively). In comparison, for five of the eight hospital-based studies the median under-reporting rate for more serious or severe ADRs remained high (95%). The median under-reporting rate was lower for 19 studies investigating specific serious/severe ADR-drug combinations but was still high at 85%.This systematic review provides evidence of significant and widespread under-reporting of ADRs to spontaneous reporting systems including serious or severe ADRs. Further work is required to assess the impact of under-reporting on public health decisions and the effects of initiatives to improve reporting such as internet reporting, pharmacist/nurse reporting and direct patient reporting as well as improved education and training of healthcare professionals.

Prescription-event monitoring and reporting of adverse drug reactions

Newly marketed drugs in the UK are marked with a black triangle, indicating that doctors should report all adverse drug reactions associated with them to the Committee on Safety of Medicines (CSM). However, under-reporting of adverse reactions is frequent. Our aim was to establish what types of adverse reactions are under-reported to the CSM by family doctors who work in England. We used prescription-event monitoring data obtained for 15 newly marketed drugs. Only 9% (376) of 4211 events found on prescription-event monitoring were reported to the CSM. However, 53% (27) of 51 events classified as serious adverse drug reactions were reported. Overall, serious events were five times more likely to be reported to the CSM than non-serious events. Our results should not be extrapolated to calculate incidence rates of adverse drug reactions in the community from spontaneous reports.

Cardiovascular events in users of sildenafil: results from first phase of prescription event monitoring in England

Sildenafil is used to treat erectile dysfunction, and prescription on the NHS is restricted. We are conducting a study of prescription event monitoring for sildenafil in England, the first phase of which investigates possible short term effects in a cohort of about 5000 users. In view of the interest in myocardial infarction as a possible short term side effect1 we report on an analysis of selected cardiovascular events reported in the first phase. Prescription event monitoring has been described elsewhere.2 Patients were identified from NHS prescriptions in England. Simple questionnaires were posted to the prescribing general practitioners about five months after the first prescription. These forms requested reporting of events after the drug had been prescribed. An “event” was any new diagnosis, any reason for referral to a consultant or admission to hospital, unexpected deterioration (or improvement) in a …

A Large Candidate Gene Survey Identifies the KCNE1 D85N Polymorphism as a Possible Modulator of Drug-Induced Torsades de Pointes

Background— Drug-induced long-QT syndrome (diLQTS) is an adverse drug effect that has an important impact on drug use, development, and regulation. We tested the hypothesis that common variants in key genes controlling cardiac electric properties modify the risk of diLQTS. Methods and Results— In a case-control setting, we included 176 patients of European descent from North America and Europe with diLQTS, defined as documented torsades de pointes during treatment with a QT-prolonging drug. Control samples were obtained from 207 patients of European ancestry who displayed <50 ms QT lengthening during initiation of therapy with a QT-prolonging drug and 837 control subjects from the population-based KORA study. Subjects were successfully genotyped at 1424 single-nucleotide polymorphisms (SNPs) in 18 candidate genes including 1386 SNPs tagging common haplotype blocks and 38 nonsynonymous ion channel gene SNPs. For validation, we used a set of cases (n=57) and population-based control subjects of European descent. The SNP KCNE1 D85N (rs1805128), known to modulate an important potassium current in the heart, predicted diLQTS with an odds ratio of 9.0 (95% confidence interval, 3.5–22.9). The variant allele was present in 8.6% of cases, 2.9% of drug-exposed control subjects, and 1.8% of population control subjects. In the validation cohort, the variant allele was present in 3.5% of cases and in 1.4% of control subjects. Conclusions— This high-density candidate SNP approach identified a key potassium channel susceptibility allele that may be associated with the rare adverse drug reaction torsades de pointes.

Sedation with “non-sedating” antihistamines: four prescription-event monitoring studies in general practice

OBJECTIVES To investigate the frequency with which sedation was reported in post-marketing surveillance studies of four second generation antihistamines: loratadine, cetirizine, fexofenadine, and acrivastine. DESIGN Prescription-event monitoring studies. SETTING Prescriptions were obtained for each cohort in the immediate post-marketing period. SUBJECTS Event data were obtained for a total of 43 363 patients. MAIN OUTCOME MEASURES Reporting of sedation or drowsiness. RESULTS The odds ratios (adjusted for age and sex) for the incidence of sedation were 0.63 (95% confidence interval 0.36 to 1.11; P=0.1) for fexofenadine; 2.79 (1.69 to 4.58; P<0.0001) for acrivastine, and 3.53 (2.07 to 5.42; P<0.0001) for cetirizine compared with loratadine. No increased risk of accident or injury was evident with any of the four drugs. CONCLUSIONS Although the risk of sedation was low with all four drugs, fexofenadine and loratadine may be more appropriate for people working in safety critical jobs.

Common Variation in the NOS1AP Gene Is Associated With Drug-Induced QT Prolongation and Ventricular Arrhythmia

OBJECTIVES This study sought to determine whether variations in NOS1AP affect drug-induced long QT syndrome (LQTS). BACKGROUND Use of antiarrhythmic drugs is limited by the high incidence of serious adverse events including QT prolongation and torsades de pointes. NOS1AP gene variants play a role in modulating QT intervals in healthy subjects and severity of presentation in LQTS. METHODS This study carried out an association study using 167 single nucleotide polymorphisms (SNP) spanning the NOS1AP gene in 58 Caucasian patients experiencing drug-induced LQTS (dLQTS) and 87 Caucasian controls from the DARE (Drug-Induced Arrhythmia Risk Evaluation) study. RESULTS The rs10800397 SNP was significantly associated with dLQTS (odds ratio [OR]: 3.3, 99.95% confidence interval [CI]: 1.0 to 10.8, p = 3.7 × 10(-4)). The associations were more pronounced in the subgroup of amiodarone users, in which 3 SNPs, including rs10800397, were significantly associated (most significant SNP: rs10919035: OR: 5.5, 99.95% CI: 1.1 to 27.9, p = 3.0 × 10(-4)). We genotyped rs10919035 in an independent replication cohort of 28 amiodarone dLQTS cases versus 173 control subjects (meta-analysis of both studies: OR: 2.81, 99.95% CI: 1.62 to 4.89, p = 2.4 × 10(-4)). Analysis of corrected QT interval among 74 control subjects from our dataset showed a similar pattern of significance over the gene region as the case-control analysis. This pattern was confirmed in 1,480 control subjects from the BRIGHT (British Genetics of Hypertension Study) cohort (top SNP from DARE: rs12734991 in meta-analysis: increase in corrected QT interval per C allele: 9.1 ± 3.2 ms, p = 1.7 × 10(-4)). CONCLUSIONS These results provide the first demonstration that common variations in the NOS1AP gene are associated with a significant increase in the risk of dLQTS. This study suggests that common variations in the NOS1AP gene may have relevance for future pharmacogenomic applications in clinical practice permitting safer prescription of drugs for vulnerable patients.

Causal association in pharmacovigilance and pharmacoepidemiology: thoughts on the application of the Austin Bradford-Hill criteria.

The methods used for the evaluation of drug safety signals (including major signals leading to withdrawal of products from the market) are inconsistent and sometimes of poor quality. While the assessment of the safety of medicines needs to consider specific issues such as drug interactions and variation in compliance, the general principles, which are used to study environmental hazards, can be applied for this purpose. The criteria proposed by Sir Austin Bradford-Hill more than 35 years ago for attributing disease causation to environmental factors have been used widely in epidemiology, are applicable to pharmacovigilance and pharmacoepidemiology.The Austin Bradford-Hill criteria include strength, consistency, specificity, temporality, biological gradient, plausibility, coherence, experimental evidence and analogy. The paper reviews each of these criteria with emphasis on pharmacovigilance and pharmacoepidemiology and with some examples. The application of the Austin Bradford-Hill criteria to the evaluation of causal association in pharmacovigilance and pharmacoepidemiology is very useful. However, it requires understanding of the limitations of the data, such as, under-reporting, poor quality of information from third parties and misclassification. Further work is required to develop strategies to handle these limitations.

An investigation into drug products withdrawn from the EU market between 2002 and 2011 for safety reasons and the evidence used to support the decision-making

Objectives The objective of this study was to determine the nature of evidence used to support the withdrawal of marketing authorisations of drug products for safety reasons throughout the European Union (EU) between 2002 and 2011. Setting Products withdrawn, either by a medicines agency or a marketing authorisation holder, during the period 2002–2011 were identified by conducting detailed searches of the WHO, the European Medicines Agency (EMA) and national medicines agency websites throughout the EU plus Norway, Iceland and Liechtenstein. The scientific evidence used to support the decision was identified from a search within PubMed, the EMA and national medicines agencies websites. Information about spontaneous case reports entered into EudraVigilance and unavailable on the EMA website was received by email from the EMA. Results 19 drugs were withdrawn from the market, throughout the EU, for safety reasons from 2002 to 2011. Case reports were cited in 95% of withdrawals (18/19) and case–control studies (4/19), cohort studies (4/19), randomised controlled trials (RCTs) (12/19) or meta-analysis (5/19) were cited in 63% of withdrawals (12/19). Cardiovascular events or disorders were the main reason for withdrawal (9/19), followed by hepatic disorders (4/19) and neurological or psychiatric disorders (4/19). Conclusions This study has shown that the level of evidence used to support drug withdrawal has improved during the past 10 years, with an increased use of case–control studies, cohort studies, RCTs and meta-analyses. This research has demonstrated that such studies have contributed to decision-making in almost two-thirds of cases.

Pharmacovigilance study of alendronate in England.

Alendronate sodium is an aminobiphosphonate, an analog of inorganic pyrophosphate, indicated for the treatment of osteoporosis in post-menopausal women. We analyzed events reported in patients prescribed alendronate by general practitioners (GPs) in England. A non-interventional observational cohort study was conducted using the technique of prescription event monitoring (PEM). Exposure data were obtained from dispensed prescriptions issued between October 1995 and January 1997. Outcome data were obtained by sending questionnaires to prescribing GPs. The cohort comprised 11,916 patients. Events most frequently reported as suspected adverse drug reactions and reason for stopping alendronate were recognized gastrointestinal events listed in the Summary of Product Characteristics. These included nausea/vomiting, abdominal pain, dyspepsia, esophagitis and esophageal reflux. Events with the highest incidence density (ID1 per 1000 patient months treatment) were dyspeptic conditions (32.2), nausea/vomiting (20.8) and abdominal pain (13.8). The term dyspeptic conditions included dyspepsia, esophagitis, esophageal reflux, duodenitis, gastritis and heartburn. Serious suspected adverse reactions possibly related to alendronate were single reports of angioedema, erythema multiforme, hypercalcemia and hypocalcemia. There were 540 deaths in this elderly cohort. This study suggests that alendronate appears to be well tolerated, though there may be risk of developing gastrointestinal side effects including esophagitis and esophageal ulcers.

Adverse effects associated with the use of donepezil in general practice in England

Donepezil is an acetylcholinesterase inhibitor indicated for the symptomatic treatment of mild to moderate Alzheimers disease. It is reported to have a relatively favourable side-effect profile. We report here on a pharmacovigilance study carried out post-marketing in England. An observational cohort study using the technique of Prescription-Event Monitoring was carried out. Some 1762 patients (mean age 72.9 years; 42% male) were followed up for 6 months minimum. The commonest adverse events were nausea, diarrhoea, malaise, dizziness and insomnia. Aggression, agitation and abnormal dreams were uncommonly associated with the drug. There were no cardiac rhythm disturbances or liver disorders causally associated. The commonest adverse drug reactions are already reported in the product information. Given the relatively small size of this cohort, the signals of abnormal dreams and psychiatric disturbance as possible adverse drug reactions need further investigation in carefully planned studies.