Evaluating risk detection methods to uncover ontogenic-mediated adverse drug effect mechanisms in children

BACKGROUND

Identifying adverse drugs effects (ADEs) in children, overall and within pediatric age groups, is essential for preventing disability and death from marketed drugs. At the same time, however, detection is challenging due to dynamic biological processes during growth and maturation, called ontogeny, that alter pharmacokinetics and pharmacodynamics. As a result, methodologies in pediatric drug safety have been limited to event surveillance and have not focused on investigating adverse event mechanisms. There is an opportunity to identify drug event patterns within observational databases for evaluating ontogenic-mediated adverse event mechanisms. The first step of which is to establish statistical models that can identify temporal trends of adverse effects across childhood.

RESULTS

Using simulation, we evaluated a population stratification method (the proportional reporting ratio or PRR) and a population modeling method (the generalized additive model or GAM) to identify and quantify ADE risk at varying reporting rates and dynamics. We found that GAMs showed improved performance over the PRR in detecting dynamic drug event reporting across child development stages. Moreover, GAMs exhibited normally distributed and robust ADE risk estimation at all development stages by sharing information across child development stages.

CONCLUSIONS

Our study underscores the opportunity for using population modeling techniques, which leverage drug event reporting across development stages, as biologically-inspired detection methods for evaluating ontogenic mechanisms.

Adverse Drug Reactions Across the Age Continuum: Epidemiology, Diagnostic Challenges, Prevention, and Treatments

Adverse drug reactions (ADRs) are common and important complications of drug therapy for children. The risk for ADRs changes over childhood, as do the nature and types of ADRs. Importantly, the risk and nature of ADRs in children are markedly different from those of adults, and adult data cannot be relied on to guide safe drug therapy in children. There are groups of children, notably those with complex and chronic diseases, who are at substantial risk for ADRs. The evaluation of an undesired effect during therapy is ideally accomplished by an organized approach that is a skill that clinicians who care for children-especially those children at high risk for ADRs must have. Additionally, clinicians as well as drug regulatory agencies and industry need to be both vigilant and astute as well as aware that ADRs in children are often different in nature and frequency from those in adults. The increasing use of pharmacogenomics to guide drug dosing and the increasing number of biological agents will provide new sets of challenges to clinicians over the next decade.

Vaccine Case-Population: A New Method for Vaccine Safety Surveillance

INTRODUCTION

The case-population approach compares exposure among cases to that of their source population. By using aggregated data to estimate the denominator, this approach can provide a real-time estimate of an association that could be particularly valuable to explore urgent vaccine safety concerns and to generate signals during a vaccine campaign.

OBJECTIVE

Our objective was to present the vaccine case-population method, a method derived from the case-population approach and adapted for vaccine safety surveillance, and to test it using several published examples.

METHODS

For the vaccine case-population method, exposure in the population is estimated from the sum of at-risk periods using the number of vaccinated individuals, or data of vaccine sales, and the at-risk period considered for the vaccine-event pair. The vaccine case-population method was applied to data from published case-control studies retrieved from the MEDLINE database and having quantified risks associated with vaccines. Odds ratios derived from the vaccine case-population method were compared with those from published case-control studies.

RESULTS

A total of 20 vaccine-event pairs were retrieved in which the vaccine case-population method could be applied. For all identified vaccine-event pairs, when a significant association was found using the vaccine case-population method, a significant association was also found in the corresponding case-control study. Conversely, when no association was found by the vaccine case-population method, no association was found in the corresponding case-control study.

CONCLUSION

These results suggest that the vaccine case-population method can produce coherent conclusions and may be used in the future for prospective investigation of urgent vaccine safety concerns or for the prospective generation of vaccine safety signals. This method could also be used to identify selection bias from cases excluded from the case-control study.

Identifying associations between maternal medication use and birth defects using a case-population approach: an exploratory study on signal detection

BACKGROUND

The effects of many drugs on the unborn child are unknown. In a case-population design, drug exposure of cases is compared with that of a source population; this kind of study can be useful for generating signals.

OBJECTIVE

To see whether a comparison of drug use rates from the birth defect registry EUROCAT NNL (cases) with prescription rates from a population-based prescription database, the IADB (population), could be used to detect signals of teratogenic risk of drugs.

METHODS

We defined 3,212 cases from the EUROCAT NNL database, a population-based birth defect registry in the Northern Netherlands and 29,223 population controls from the IADB, a prescription database with data from community pharmacies in the same geographical area, born between 1998 and 2008. We classified the malformations of the 3,212 cases into several malformation groups according to organ system (based on the International Classification of Diseases codes and the EUROCAT guidelines). If a child had multiple malformations in several organ systems (n = 253, 7.9 %), he/she was counted in all the categories represented. For several groups of malformations we calculated rate ratios (RR) and 95 % confidence intervals for drugs acting on the central nervous system and for drugs considered to be safe for use in pregnancy. The RRs were based on first-trimester drug use rates from the cases in the EUROCAT NNL database and prescription rates from the population controls in the IADB.

RESULTS

For drugs acting on the central nervous system we found significantly increased RRs for the anti-epileptic drug valproic acid and for some selective serotonin reuptake inhibitors. For drugs considered to be safe only the anti-hypertensive methyldopa showed significantly increased RRs.

CONCLUSION

We show that a case-population study is a suitable method for detecting signals of possible teratogenicity, provided that the teratogenic effects and the drugs under study are as specific as possible and the drugs are widely used.

Psychostimulants in moderate to severe affective disorder: a systematic review of randomized controlled trials

BACKGROUND

Despite antidepressant therapy of appropriate trial duration and dose optimization, 50-60% of depressed patients have an adequate treatment response, whereas only 35-40% achieve remission. Psychostimulants have been suggested as potential candidates to promote acceleration of response and to alleviate residual symptoms of depression.

AIMS

In this review results from randomized clinical trials (RCTs) exploring the efficacy of psychostimulants in the treatment of major depressive disorder (MDD) were analyzed to clarify the current empirically founded evidence for clinical approaches involving psychostimulants.

METHOD

Literature research via PubMed retrieved 846 articles. 18 RCTs reporting on the use of psychostimulants in the treatment of adult patient populations, suffering from moderate-severe depression and having no other concomitant medical illnesses, were included in this review. 14 articles provided results for unipolar depression, two for bipolar depression, whereas two articles presented mixed samples of unipolar and bipolar patients.

RESULTS

Five different psychostimulants were evaluated: modafinil, methylphenidate, dexamphetamine, methylamphetamine and pemoline. Two studies examining modafinil demonstrated significant ameliorating characteristics pertaining to symptoms of depression. No clear evidence for the effectiveness of traditional psychostimulants in the therapeutic management of MDD was found. In general the quality of included trials was poor since the majority was of short-term duration, comprising relatively small sample sizes and some, especially older studies, were methodologically flawed.

CONCLUSION

Clearly larger well designed placebo-controlled studies with longer follow-up accompanied by evaluations of tolerance/dependence are warranted before psychostimulants can be recommended in routine clinical practice for the treatment of MDD.

Adverse drug reactions in hospitalized pediatric patients of Saudi Arabian University Hospital and impact of pharmacovigilance in reporting ADR

OBJECTIVES

Children are more vulnerable to ADRs, and this susceptibility is compounded due to hospitalization. There is a lack of local data regarding the potential risk of ADRs in hospitalized pediatric patients. Therefore, this study is designed to identify the frequent nature, severity of adverse drug reactions, drugs implicated and factors influencing ADRs.

METHODS

Intensive monitoring study of ADRs was done in hospitalized pediatric patients of King Abdulaziz University Hospital, Jeddah from January to December 2011, with an analogous retrospective study for the preceding year to determine incidence rate, demographic aspects, causality appraisal, polypharmacy, body organs/systems involved and drugs implicated in ADR. Comparison of the two data was done to determine the impact of pharmacovigilance.

RESULTS

Incidence rate of ADRs in retrospective study was (4.50%) and (8.2%) in prospective study. ADR was more in patients who received 5-6 drugs, which was (15.5%) in retrospective study and (22.1%) in prospective study. Regarding age, it was the highest in patients of 0-1 year of age which was (40.7%) in retrospective study and (38.8%) in prospective study. Anti-infective agents were the most frequently involved in ADR (40.8%) in prospective study and (48.2%) and retrospective study. This study also demonstrated that, there was high susceptibility of the skin to the ADR which was (37%) in retrospective study and (42.9%) in prospective study. None of the ADRs proved to be fatal.

CONCLUSION

Well premeditated intensive monitoring approach in pharmacovigilance amplifies the ADR detection, which can persuade healthcare providers into more drug safety.

The case-population study design: an analysis of its application in pharmacovigilance

BACKGROUND

The case-population approach or population-based case-cohort approach is derived from the case-control design and consists of comparing past exposure to a given risk factor in subjects presenting a given disease or symptom (cases) with the exposure rate to this factor in the whole cohort or in the source population of cases. In the same way as the case-control approach, the case-population approach measures the disproportionality of exposure between cases of a given disease and their source population expressed in the form of an odds ratio approximating the ratio of the risks in exposed and not-exposed populations (relative risk).

OBJECTIVE

The aim of this study was to (i) present the case-population principle design in a way understandable for non-statisticians; (ii) propose the easiest way of using it for pharmacovigilance purposes (mainly alerting and hypothesis testing); (iii) propose simple formulae for computing an odds ratio and its confidence interval; (iv) apply the approach to several practical and published examples; and (v) discuss its pros and cons in the context of real life.

METHODS

The approach used is derived from that comparing two rates expressed as person-time denominators. It allows easy computation of an odds ratio and its confidence interval under several hypotheses. Results obtained with the case-population approach were compared with those of case-control studies published in the literature.

RESULTS

Relevance and limits of the proposed approach are illustrated by examples taken from published pharmacoepidemiological studies. The odds ratio (OR) reported in a European case-control study on centrally acting appetite suppressants and primary pulmonary hypertension was 23.1 (95% CI 6.9, 77.7) versus 31 (95% CI 16.2, 59.2) using the case-population approach. In the European case-control studies SCAR (Severe Cutaneous Adverse Reactions) and EuroSCAR on the risk of toxic epidermal necrolysis associated with the use of medicines, the OR for cotrimoxazole was 160 and 102, respectively, versus 44.4 using the case-population approach. Similarly, these two case-control studies found ORs of 12 and 72 for carbamazepine versus 24.4 using the case-population approach, 8.7 and 16 for phenobarbital versus 21.9, 12 for piroxicam (analysed in the SCAR study only) versus 14.5, and 5.5 and 18 for allopurinol versus 3.4 using the case-population approach.

CONCLUSIONS

Being based on the estimate derived from sales statistics of the total exposure time in the source population of cases, the method can be used even when there is no information about the actual number of exposed subjects in this population. Although the case-population approach suffers from limitations stemming from its main advantage, i.e. impossibility to control possible confounders and to quantify the strength of associations due to the absence of an ad hoc control group, it is particularly useful to use in routine practice, mainly for purposes of signal generation and hypothesis testing in drug surveillance.

Safety assessment in pediatric studies

It typically takes many years before an association of a drug with a rare, serious adverse reaction is established. As related to pediatric drug use, evidence is even more erratic, as most drugs are used off labels. To enhance child safety, there is an urgent need to develop robust and rapid methods to identify such associations in as timely a manner as possible. In this chapter, several novel methods, both clinically based pharmacoepidemiological approaches and laboratory-based methods, are described.

Eosinophilic hepatitis in an adolescent during lisdexamfetamine dimesylate treatment for ADHD

We describe here the case of an adolescent who developed eosinophilic hepatitis during treatment for attention-deficit/hyperactivity disorder with lisdexamfetamine dimesylate (Vyvanse [Shire US Inc, Wayne, PA]). A 14-year-old boy presented to his primary care provider with abdominal pain and worsening jaundice. A diagnosis of hepatitis was made with biochemical markers, but evaluation failed to provide an etiology. Worsening hepatitis prompted hospitalization and initiation of steroids for presumed autoimmune hepatitis. A subsequent liver biopsy showed evidence of eosinophilic hepatitis. Known causes of eosinophilic hepatitis were ruled out, and a presumptive diagnosis of reaction to lisdexamfetamine dimesylate was made. Discontinuation of the medication led to resolution of the hepatitis and normalization of the liver biopsy. To our knowledge, this is the first report of hepatic injury attributed to lisdexamfetamine dimesylate.

Drug-induced liver injury: what was new in 2008?

BACKGROUND

Given the number of publications appearing annually regarding drug-induced liver injury (DILI), there remains a need to concisely summarize each year's new crop of case series and reports as well as the advances in mechanisms of liver injury and in the field of pharmacogenomics relating to DILI.

OBJECTIVE

To present an up-to-date review of the past year's most important clinical studies and reports of DILI, placing them into context of previous publications.

METHODS

A Medline search was conducted of all manuscripts appearing in the fields "hepatotoxicity" and "drug-induced liver injury" during the calendar year 2008. The most clinically relevant English language case reports and studies exploring mechanisms and risk factors for DILI were then chosen for review, and supplemented with older literature where appropriate.

CONCLUSIONS

As in past years, 2008 was replete with publications dealing with virtually all facets of DILI, including updated incidence and prevalence data, as well as the latest information regarding mechanisms of liver injury. Data from the first 300 patients in the National Institute of Health-sponsored DILI Network registry of > 100 non-acetaminophen causes were presented. Antimicrobials and CNS drugs were responsible for > 60% of cases, with herbals and dietary supplements being increasingly reported. Identification of genetic predispositions to DILI is coming of age with the FDA calling for the testing of human leukocyte antigen B(*)5701 before the use of abacavir to reduce the risk of hypersensitivity reactions. Several groups emphasized the pitfalls in utilizing Roussel Uclaf Causality Assessment Method and other causality assessment methodologies, and an updated review appeared on the use of potentially hepatotoxic medications in patients with underlying liver disease.

Off-label psychopharmacologic prescribing for children: history supports close clinical monitoring

The review presents pediatric adverse drug events from a historical perspective and focuses on selected safety issues associated with off-label use of medications for the psychiatric treatment of youth. Clinical monitoring procedures for major psychotropic drug classes are reviewed. Prior studies suggest that systematic treatment monitoring is warranted so as to both minimize risk of unexpected adverse events and exposures to ineffective treatments. Clinical trials to establish the efficacy and safety of drugs currently being used off-label in the pediatric population are needed. In the meantime, clinicians should consider the existing evidence-base for these drugs and institute close clinical monitoring.