The long and growing list of non-antiarrhythmic drugs associated with prolongation of the QT interval of the electrocardiogram has generated concern not only for regulatory interventions leading to drug withdrawal, but also for the unjustified view that QT prolongation is usually an intrinsic effect of a whole therapeutic class [e.g. histamine H(1) receptor antagonists (antihistamines)], whereas, in many cases, it is displayed only by some compounds within a given class of non-antiarrhythmic drugs because of an effect on cardiac repolarisation. We provide an overview of the different classes of non-antiarrhythmic drugs reported to prolong the QT interval (e.g. antihistamines, antipsychotics, antidepressants and macrolides) and discusses the clinical relevance of the QT prolonging effect. Drug-induced torsade de pointes are sometimes considered idiosyncratic, totally unpredictable adverse drug reactions, whereas a number of risk factors for their occurrence is now recognised. Widespread knowledge of these risk factors and implementation of a comprehensive list of QT prolonging drugs becomes an important issue. Risk factors include congenital long QT syndrome, clinically significant bradycardia or heart disease, electrolyte imbalance (especially hypokalaemia, hypomagnesaemia, hypocalcaemia), impaired hepatic/renal function, concomitant treatment with other drugs with known potential for pharmacokinetic/pharmacodynamic interactions (e.g. azole antifungals, macrolide antibacterials and class I or III antiarrhythmic agents). This review provides insight into the strategies that should be followed during a drug development program when a drug is suspected to affect the QT interval. The factors limiting the predictive value of preclinical and clinical studies are also outlined. The sensitivity of preclinical tests (i.e. their ability to label as positive those drugs with a real risk of inducing QT pronglation in humans) is sufficiently good, but their specificity (i.e. their ability to label as negative those drugs carrying no risk) is not well established. Verapamil is a notable example of a false positive: it blocks human ether-a-go-go-related (HERG) K(+) channels, but is reported to have little potential to trigger torsade de pointes. Although inhibition of HERG K(+) channels has been proposed as a primary test for screening purposes, it is important to remember that several ion currents are involved in the generation of the cardiac potential and that metabolites must be specifically tested in this in vitro test. At the present state of knowledge, no preclinical model has an absolute predictive value or can be considered as a gold standard. Therefore, the use of several models facilitates decision making and is recommended by most experts in the field.

OBJECTIVETo analyze the association between pioglitazone use and bladder cancer through a spontaneous adverse event reporting system for medications.RESEARCH DESIGN AND METHODSCase/noncase bladder cancer reports associated with antidiabetic drug use were retrieved from the U.S. Food and Drug Administration (FDA) Adverse Event Reporting System (AERS) between 2004 and 2009 and analyzed by the reporting odds ratio (ROR).RESULTSNinety-three reports of bladder cancer were retrieved, corresponding to 138 drug-reaction pairs (pioglitazone, 31; insulin, 29; metformin, 25; glimepiride, 13; exenatide, 8; others, 22). ROR was indicative of a definite risk for pioglitazone (4.30 [95% CI 2.82–6.52]), and a much weaker risk for gliclazide and acarbose, with very few cases being treated with these two drugs (6 and 4, respectively).CONCLUSIONSIn agreement with preclinical and clinical studies, AERS analysis is consistent with an association between pioglitazone and bladder cancer. This issue needs constant epidemiologic surveillance and urgent definition by more specific studies.

This has fostered discussion on the molecular mechanisms underlying the class-III antiarrhythmic effect shared by apparently disparate classes of drugs, on the clinical relevance of this side effect and on possible guidelines to be followed by drug companies, ethics committees and regulatory agencies in the risk-benefit assessment of new and licensed drugs. This review provides an update on the different classes of non-cardiac drugs reported to prolong the QT interval (e.g. histamine H1-receptor antagonists, antipsychotics, antidepressants and macrolides), on the possible underlying molecular mechanisms and on the clinical relevance of the QT prolonging effect. Identification and widespread knowledge of risk factors that may precipitate prolongation of the QT interval into life-threatening arrhythmias becomes an important issue. Risk factors include congenital long QT syndrome, clinically significant bradycardia or heart disease, electrolyte imbalance (especially hypokalaemia, hypomagnesaemia), impaired hepatic/renal function and concomitant treatment with other drugs with known potential for pharmacokinetic/ pharmacodynamic interactions (e.g. azole antifungals, macrolide antibacterials and class-I or -III antiarrhythmic agents). Future perspectives for drug research and development are also briefly outlined.

This list should be considered as a starting point to call for consensus on: (1) the criteria used to generate the list, (2) possible ways to implement the use of this list as a quick reference for clinicians, for instance by providing a "proarrhythmic score" for each drug, and (3) inclusion/exclusion of a given agent into the list on the basis of evidence that may not be available to us.

The periodic e-mail update on the safety of drugs represents an effective and inexpensive way to raise the awareness of GPs on the importance of spontaneous ADR reporting. Since the outcome of the intervention seemed to disappear after the intervention was stopped, there appears to be a need to adopt a policy of regular updates and educational strategies for health professionals.