Pharmacogenetics of drug-induced arrhythmias: a feasibility study using spontaneous adverse drug reactions reporting data

QTc prolongation in short-term treatment of schizophrenia patients: effects of different antipsychotics and genetic factors

Antipsychotics are effective in treating schizophrenia but may lead to a higher cardiovascular risk due to QTc prolongation. Besides drugs, genetic and clinical factors may contribute to QTc prolongation. The aim of this study is to examine the effect of candidate genes known for QTc prolongation and their interaction with common antipsychotics. Thus, 199 patients were genotyped for nine polymorphisms in KCNQ1, KCNH2, SCN5A, LOC10537879, LOC101927066, NOS1AP and NUBPL. QTc interval duration was measured before treatment and weekly for 5 weeks while being treated with risperidone, quetiapine, olanzapine, amisulpride, aripiprazole and haloperidol in monotherapy. Antipsychotics used in this study showed a different potential to affect the QTc interval. We found no association between KCNH2, KCNQ1, LOC10537879, LOC101927066, NOS1AP and NUBPL polymorphisms and QTc duration at baseline and during antipsychotic treatment. Mixed general models showed a significant overall influence of SCN5A (H558R) on QTc duration but no significant interaction with antipsychotic treatment. Our results do not provide evidence for an involvement of candidate genes for QTc duration in the pathophysiology of QTc prolongation by antipsychotics during short-term treatment. Further association studies are needed to confirm our findings. With a better understanding of these interactions the cardiovascular risk of patients may be decreased.

Time-to-Onset Analysis of Drug-Induced Long QT Syndrome Based on a Spontaneous Reporting System for Adverse Drug Events

Long QT syndrome (LQTS) is a disorder of the heart’s electrical activity that infrequently causes severe ventricular arrhythmias such as a type of ventricular tachycardia called torsade de pointes (TdP) and ventricular fibrillation, which can be fatal. There have been no previous reports on the time-to-onset for LQTS based on data from spontaneous reporting systems. The aim of this study was to assess the time-to-onset of LQTS according to drug treatment. We analyzed the association between 113 drugs in 37 therapeutic categories and LQTS including TdP using data obtained from the Japanese Adverse Drug Event Report database. For signal detection, we used the reporting odds ratio (ROR). Furthermore, we analyzed the time-to-onset data and assessed the hazard type using the Weibull shape parameter. The RORs (95% confidence interval) for bepridil, amiodarone, pilsicainide, nilotinib, disopyramide, arsenic trioxide, clarithromycin, cibenzoline, donepezil, famotidine, sulpiride, and nifekalant were 174.4 (148.6–204.6), 17.3 (14.7–20.4), 52.0 (43.4–62.4), 13.9 (11.5–16.7), 69.3 (55.3–86.8), 54.2 (43.2–68.0), 4.7 (3.8–5.8), 19.9 (15.9–25.0), 8.1 (6.5–10.1), 3.2 (2.5–4.1), 7.1 (5.5–9.2), and 254.8 (168.5–385.4), respectively. The medians and quartiles of time-to-onset for aprindine (oral) and bepridil were 20.0 (11.0–35.8) and 18.0 (6.0–43.0) days, respectively. The lower 95% confidence interval of the shape parameter β of bepridil was over 1 and the hazard was considered to increase over time.Our study indicated that the pattern of LQTS onset might differ among drugs. Based on these results, careful long-term observation is recommended, especially for specific drugs such as bepridil and aprindine. This information may be useful for the prevention of sudden death following LQTS and for efficient therapeutic planning.

Pharmacogenetics of Drug-Induced QT Interval Prolongation: An Update

A prolonged QT interval is an important risk factor for ventricular arrhythmias and sudden cardiac death. QT prolongation can be caused by drugs. There are multiple risk factors for drug-induced QT prolongation, including genetic variation. QT prolongation is one of the most common reasons for withdrawal of drugs from the market, despite the fact that these drugs may be beneficial for certain patients and not harmful in every patient. Identifying genetic variants associated with drug-induced QT prolongation might add to tailored pharmacotherapy and prevent beneficial drugs from being withdrawn unnecessarily. In this review, our objective was to provide an overview of the genetic background of drug-induced QT prolongation, distinguishing pharmacokinetic and pharmacodynamic pathways. Pharmacokinetic-mediated genetic susceptibility is mainly characterized by variation in genes encoding drug-metabolizing cytochrome P450 enzymes or drug transporters. For instance, the P-glycoprotein drug transporter plays a role in the pharmacokinetic susceptibility of drug-induced QT prolongation. The pharmacodynamic component of genetic susceptibility is mainly characterized by genes known to be associated with QT interval duration in the general population and genes in which the causal mutations of congenital long QT syndromes are located. Ethnicity influences susceptibility to drug-induced QT interval prolongation, with Caucasians being more sensitive than other ethnicities. Research on the association between pharmacogenetic interactions and clinical endpoints such as sudden cardiac death is still limited. Future studies in this area could enable us to determine the risk of arrhythmias more adequately in clinical practice.

Pharmacogenovigilance: a pharmacogenomics pharmacovigilance program

In this report, we review the importance of pharmacovigilance in detecting postmarketing adverse drug events and the potential for developing pharmacogenovigilance programs by integrating pharmacogenomics with pharmacovigilance. We propose to start developing such a program in primary healthcare systems that use basic features of electronic medical records and have access to large numbers of patients commonly prescribed drugs. Such programs, if carefully designed, may grow over time and hopefully enhance the collection and interpretation of useful data for the clinical applications of pharmacogenomics testing.

Case ascertainment and estimated incidence of drug-induced long-QT syndrome: study in Southwest France

AIMS

The aim of this study was to investigate the incidence and reporting rate of drug-induced long-QT syndrome (LQTS) in France [defined by evidence of torsades de pointes (TdP), QT prolongation and exposure to a relevant drug] and to assess feasibility of case collection for drug-induced LQTS.

METHODS

A retrospective population-based study was carried out in Southwest France in five institutions: three main hospitals, one private clinic and one cardiac emergency unit, searched from 1 January 1999 to 1 January 2005 (population coverage of 614 000). The study population consisted of 861 cases with International Classification of Diseases-10 diagnostic codes for ventricular tachycardia (I147.2), ventricular fibrillation (I149.0) and sudden cardiac death (I146.1) from hospital discharge summaries, supplemented by cases reported to national or regional pharmacovigilance systems, and voluntary reporting by physicians, validated according to internationally defined criteria for drug-induced LQTS.

RESULTS

Of 861 patients coded with arrhythmias or sudden cardiac death, there were 40 confirmed surviving acquired cases of drug-induced LQTS. We estimated that the incidence of those who survive to reach hospital drug-induced LQTS is approximately 10.9 per million annually in France (95% confidence interval 7.8, 14.8).

CONCLUSIONS

Many cases of drug-induced LQTS may not survive before they reach hospital, as the reporting rate for drug-induced LQTS identified through the cardiology records and also reported to pharmacovigilance systems for the Midi-Pyrenees area is 3/40 (7.5%). Using the methods outlined it is possible to assemble cases to study genetic susceptibility to drug-induced LQTS and adapt these methods more widely.

EUDRAGENE: European collaboration to establish a case–control DNA collection for studying the genetic basis of adverse drug reactions

Type B adverse drug reactions (ADRs) are often serious, limit the usefulness of drugs that are otherwise effective, and increase the risks of drug development as they often lead to postmarketing withdrawal. There is evidence that susceptibility to at least some Type B ADRs is under strong genetic influence. Identifying genes in which variation influences susceptibility has obvious practical value for genetic testing and might also make it easier to screen molecules likely to cause ADRs at an early stage of the drug development process. Research in this area is hampered by the lack of a resource in which to study genetic determinants of susceptibility to Type B ADRs. As serious Type B ADRs are rare, case–control designs are the most frequently-used approach. The EUDRAGENE collaboration seeks to develop a resource using an international collaboration. This will provide a basis for adverse drug susceptibility genome association-wide studies using tag single nucleotide polymorphisms, or a direct approach using putative functional polymorphisms.