The risk of serious cardiac arrhythmias among cisapride users in the United Kingdom and Canada

[How to Study the Sex and Gender Effect in Biomedical Research?]

Men and women are different, but this difference has not been well reflected in clinical trials and preclinical studies of biomedical science. Gender medicine, which systematically analyzes research results according to sex and gender, has been emphasized to overcome this problem. On the other hand, researchers still have difficulty in applying gender medicine to their research. To perform rigorous gender medicine, using correct terms, a thorough literature review during research planning, appropriate statistical analysis and reporting, and cautious interpretation of the results are necessary. Applying gender medicine will increase the reproducibility of studies, promote discoveries, expand the study relevance, and ultimately improve patient care in both men and women. Here, this study reviewed the practical issues on applying gender medicine to both preclinical and clinical studies in the field of biomedical science.

Cardiovascular safety of prokinetic agents: A focus on drug-induced arrhythmias

BACKGROUND

Gastrointestinal sensorimotor dysfunction underlies a wide range of esophageal, gastric, and intestinal motility and functional disorders that collectively constitute nearly half of all referrals to gastroenterologists. As a result, substantial effort has been dedicated toward the development of prokinetic agents intended to augment or restore normal gastrointestinal motility. However, the use of several clinically efficacious gastroprokinetic agents, such as cisapride, domperidone, erythromycin, and tegaserod, is associated with unfavorable cardiovascular safety profiles, leading to restrictions in their use.

PURPOSE

The purpose of this review is to detail the cellular and molecular mechanisms that lead commonly to drug-induced cardiac arrhythmias, specifically drug-induced long QT syndrome, torsades de pointes, and ventricular fibrillation, to examine the cardiovascular safety profiles of several classes of prokinetic agents currently in clinical use, and to explore potential strategies by which the risk of drug-induced cardiac arrhythmia associated with prokinetic agents and other QT interval prolonging medications can be mitigated successfully.

Bridging the boundaries between scientists and clinicians-mechanistic hypotheses and patient stories in risk assessment of drugs

The cultural divide between scientists and clinicians has been described as undermining the advance of medical science, by hindering the production of practice-relevant research and of research-informed clinical decisions. Here, I consider the field of post-marketing risk assessment of drugs as an example of strict interdependence between basic biomedical research, clinical research, and clinical evaluation and show how it would benefit from a closer collaboration between scientists and clinicians. The risk assessment of drugs after their marketing relies on spontaneous adverse effect reports to drug agencies and on peer-reviewed case reports. I emphasize the importance of qualitative analysis of such reports for the improvement of mechanistic understanding of harmful effects of drugs. I argue that mechanistic explanations of drug effects are at least as important as determination of their frequency, in order to establish causation. An ideal risk assessment, then, verifies not only the frequency of undesired effects but also why and how the harm happens. For this purpose, the frequency or novelty of the unintended outcome, although contextually indicative, should not determine the epistemic value of a report. Details about the context that generated an unexpected outcome, instead, can offer the chance of improving causal understanding about how the intervention works. This is illustrated through examples from medical research. Mechanistic understanding is a domain of joint collaboration among (1) clinicians, in charge of detailed, qualitative reporting of patient stories about side effects, (2) qualitative clinical researchers, in charge of analyzing clinical contexts or harmful effects and formulating explanatory hypotheses, and (3) basic biomedical researchers, in charge of verifying such hypotheses. In addition, direct information flow can on one side focus clinicians' attention on knowledge gaps about drugs/effects where more research is needed, while on the other side create a more contextualized concept of mechanism among scientists.

Metoclopramide as intermittent and continuous infusions in critically ill patients: a pilot randomized clinical trial

AIM

Metoclopramide is commonly used as a prokinetic agent in critically ill patients with enteral feeding intolerance. In this study, noninferiority of metoclopramide as intermittent versus continuous infusion was examined in critically ill patients with enteral feeding intolerance.

METHODS

Forty critically ill adults patients were assigned to receive metoclopramide as either intermittent (10 mg every 6 h) or continuous (2 mg/h) infusion. Frequency of feeding intolerance and adverse effects of metoclopramide were assessed during 7 days of study.

RESULTS

Number of patients with feeding intolerance during different times of the course was not different between the groups. Although not statistically significant, diarrhea and cardiac rhythm were more common in continuous than intermittent infusion group.

CONCLUSION

Continuous and intermittent infusions of metoclopramide showed equivalent effectiveness in critically ill patients.

Pharmacological therapy of feed intolerance in the critically ills

Feed intolerance in the setting of critical illness is associated with higher morbidity and mortality, and thus requires promptly and effective treatment. Prokinetic agents are currently considered as the first-line therapy given issues relating to parenteral nutrition and post-pyloric placement. Currently, the agents of choice are erythromycin and metoclopramide, either alone or in combination, which are highly effective with relatively low incidence of cardiac, hemodynamic or neurological adverse effects. Diarrhea, however, can occur in up to 49% of patients who are treated with the dual prokinetic therapy, which is not associated with Clostridium difficile infection and settled soon after the cessation of the drugs. Hence, the use of prokinetic therapy over a long period or for prophylactic purpose must be avoided, and the indication for ongoing use of the drug(s) must be reviewed frequently. Second line therapy, such as total parenteral nutrition and post-pyloric feeding, must be considered once adverse effects relating the prokinetic therapy develop.

Current issues on safety of prokinetics in critically ill patients with feed intolerance

Feed intolerance in the setting of critical illness should be treated promptly given its adverse impact on morbidity and mortality. The technical difficulty of postpyloric feeding tube placement and the morbidities associated with parenteral nutrition prevent these approaches being considered as first-line nutrition. Prokinetic agents are currently the mainstay of therapy for feed intolerance in the critically ill. Current information is limited but suggests that erythromycin or metoclopramide (alone or in combination) are effective in the management of feed intolerance in the critically ill and not associated with significant cardiac, haemodynamic or neurological adverse effects. However, diarrhoea is a very common gastrointestinal side effect, and can occur in up to 49% of patients who receive both erythromycin and metoclopramide. Fortunately, the diarrhoea associated with prokinetic treatments has not been linked to Clostridium difficile infection and settles soon after the drugs are ceased. Therefore, prolonged or prophylactic use of prokinetics should be avoided. If diarrhoea occurs, the drugs should be stopped immediately. To minimize avoidable adverse effects the ongoing need for prokinetic drugs in these patient should be reviewed daily.

Systematic review: cardiovascular safety profile of 5-HT(4) agonists developed for gastrointestinal disorders

BACKGROUND

The nonselective 5-HT(4) receptor agonists, cisapride and tegaserod have been associated with cardiovascular adverse events (AEs).

AIM

To perform a systematic review of the safety profile, particularly cardiovascular, of 5-HT(4) agonists developed for gastrointestinal disorders, and a nonsystematic summary of their pharmacology and clinical efficacy.

METHODS

Articles reporting data on cisapride, clebopride, prucalopride, mosapride, renzapride, tegaserod, TD-5108 (velusetrag) and ATI-7505 (naronapride) were identified through a systematic search of the Cochrane Library, Medline, Embase and Toxfile. Abstracts from UEGW 2006-2008 and DDW 2008-2010 were searched for these drug names, and pharmaceutical companies approached to provide unpublished data.

RESULTS

Retrieved articles on pharmacokinetics, human pharmacodynamics and clinical data with these 5-HT(4) agonists, are reviewed and summarised nonsystematically. Articles relating to cardiac safety and tolerability of these agents, including any relevant case reports, are reported systematically. Two nonselective 5-HT(4) agonists had reports of cardiovascular AEs: cisapride (QT prolongation) and tegaserod (ischaemia). Interactions with, respectively, the hERG cardiac potassium channel and 5-HT(1) receptor subtypes have been suggested to account for these effects. No cardiovascular safety concerns were reported for the newer, selective 5-HT(4) agonists prucalopride, velusetrag, naronapride, or for nonselective 5-HT(4) agonists with no hERG or 5-HT(1) affinity (renzapride, clebopride, mosapride).

CONCLUSIONS

5-HT(4) agonists for GI disorders differ in chemical structure and selectivity for 5-HT(4) receptors. Selectivity for 5-HT(4) over non-5-HT(4) receptors may influence the agent's safety and overall risk-benefit profile. Based on available evidence, highly selective 5-HT(4) agonists may offer improved safety to treat patients with impaired GI motility.

Antidepressants and the risk of sudden cardiac death and ventricular arrhythmia

PURPOSE

To examine the association between exposure to antidepressants and emergency department or inpatient admission for sudden cardiac death and ventricular arrhythmia (SD/VA), and to examine the impact of dose and cytochrome P-450 inhibition.

METHODS

A cohort study was conducted using 1999-2003 Medicaid claims data from beneficiaries of five large states, supplemented with Medicare claims for dually eligible individuals. Exposures were prescription claims for antidepressants of interest or a reference antidepressant. Outcomes were incident first-listed emergency department or principal inpatient diagnoses indicative of SD/VA originating in the outpatient setting, an outcome previously found to have a positive predictive value of 85%.

RESULTS

In 1.3 million person-years of antidepressant exposure, we identified 4222 SD/VA outcomes for a rate of 3.3/1000 person-years (95%CI, 3.2-3.4). Compared with paroxetine (a referent with a putatively favorable cardiovascular risk profile), adjusted hazard ratios (HRs) were 0.80 (0.67-0.95) for bupropion, 1.24 (0.93-1.65) for doxepin, 0.79 (0.55-1.15) for lithium, and 1.26 (1.11-1.42) for mirtazapine. HRs for amitriptyline, citalopram, fluoxetine, nefazodone, nortriptyline, sertraline, trazodone, and venlafaxine were near unity. For antidepressants having nonnull risks (bupropion and mirtazapine), we observed no relationship with antidepressant dose and some relationships with concomitant cytochrome P-450 inhibition.

CONCLUSIONS

Of antidepressants studied, only mirtazapine had a statistically significantly greater SD/VA risk versus paroxetine. However, baseline differences between these users suggest that this finding may be attributable to residual confounding. Eleven other antidepressants had SD/VA risks no greater than that of paroxetine, thereby providing reassurance regarding the comparative cardiovascular safety of antidepressants.

Cisapride: what can we learn from the rise and fall of a prokinetic?

Cisapride, the prototype serotonergic agent, evolved from a body of research that defined the key roles of serotonergic receptors in gastrointestinal motor and sensory function. Impressed by its in vitro properties and encouraged by clinical trial data, cisapride became the drug of choice for the treatment of a wide range of motility disorders and clinicians appeared impressed by its efficacy and comfortable with its side-effect profile. Once serious cardiac events began to be reported in association with cisapride therapy, dark clouds rapidly gathered and soon enveloped the drug, leading to its widespread withdrawal from markets. What lessons can we learn from the story of cisapride? How can its brief but spectacular rise and equally sensational demise inform the development of new drugs which are so sorely needed in the management of motility and functional gastrointestinal disorders? This review explores the background to the development of cisapride, its history in clinical trials and the experience with adverse events and, in so doing, attempts to identify lessons for the future in the therapeutics of enteric neuromodulatory drugs.

Drug-induced long QT syndrome

The drug-induced long QT syndrome is a distinct clinical entity that has evolved from an electrophysiologic curiosity to a centerpiece in drug regulation and development. This evolution reflects an increasing recognition that a rare adverse drug effect can profoundly upset the balance between benefit and risk that goes into the prescription of a drug by an individual practitioner as well as the approval of a new drug entity by a regulatory agency. This review will outline how defining the central mechanism, block of the cardiac delayed-rectifier potassium current I(Kr), has contributed to defining risk in patients and in populations. Models for studying risk, and understanding the way in which clinical risk factors modulate cardiac repolarization at the molecular level are discussed. Finally, the role of genetic variants in modulating risk is described.

Validation of diagnostic codes for outpatient-originating sudden cardiac death and ventricular arrhythmia in Medicaid and Medicare claims data

PURPOSE

Sudden cardiac death (SD) and ventricular arrhythmias (VAs) caused by medications have arisen as an important public health concern in recent years. The validity of diagnostic codes in identifying SD/VA events originating in the ambulatory setting is not well known. This study examined the positive predictive value (PPV) of hospitalization and emergency department encounter diagnoses in identifying SD/VA events originating in the outpatient setting.

METHODS

We selected random samples of hospitalizations and emergency department claims with principal or first-listed discharge diagnosis codes indicative of SD/VA in individuals contributing at least 6 months of baseline time within 1999-2002 Medicaid and Medicare data from five large states. We then obtained and reviewed medical records corresponding to these events to serve as the reference standard.

RESULTS

We identified 5239 inpatient and 29 135 emergency department events, randomly selected 100 of each, and obtained 119 medical records, 116 of which were for the requested courses of care. The PPVs for an outpatient-originating SD/VA precipitating hospitalization or emergency department treatment were 85.3% (95% confidence interval [CI] = 77.6-91.2) overall, 79.7% (95%CI = 68.3-88.4) for hospitalization claims, and 93.6% (95%CI = 82.5-98.7) for emergency department claims.

CONCLUSIONS

First-listed SD/VA diagnostic codes identified in inpatient or emergency department encounters had very good agreement with clinical diagnoses and functioned well to identify outpatient-originating events. Researchers using such codes can be confident of the PPV when conducting studies of SD/VA originating in the outpatient setting.

Thorough QT Studies: Questions and Quandaries

The International Conference on Harmonisation E14 Guidance was successful in largely standardizing the conduct of the so-called thorough QT/QTc studies (TQTS). Nevertheless, there is still a spectrum of frequently encountered problems with details of design, conduct and interpretation of TQTS. Several of these challenges are reviewed here, starting with explaining that the TQTS goal is only to identify drugs for which the proarrhythmic risk might be considered excluded for the purposes of regulatory benefit-risk assessment. Suggestions are made on how to categorize and quantify or exclude proarrhythmic risk if the TQTS is positive. There is a conceptual need for TQTS, and this is discussed, together with reasons why restricted clinical registries cannot prove the absence of proarrhythmic liability of any drug. Appropriate drug doses investigated in TQTS should be derived from the maximum clinically tolerable dose rather than from the known or expected therapeutic dose. With the help of concentration-QTc modelling, the standard therapeutic dose can be omitted from TQTS, especially if the study is expected to be negative. Conditions for single-dose TQTS acceptability are reviewed. The role of the so-called positive control is assessed, contrasting the role of a same-class comparator for the investigated drug. A single 400 mg dose of moxifloxacin is advocated as the present 'gold standard' assay sensitivity test. The necessity of careful placebo control is explained and the frequency of ECG assessments is considered. The central tendency and outlier analyses are discussed, together with the correct approaches to baseline adjustment. The review concludes that the design and interpretation of TQTS must not be approached with mechanistic stereotypes, and highlights the importance of relating the QTc changes to drug plasma levels.

Use of venlafaxine compared with other antidepressants and the risk of sudden cardiac death or near death: a nested case-control study

OBJECTIVE

To assess whether use of the antidepressant venlafaxine is associated with an increased risk of sudden cardiac death or near death compared with other commonly used antidepressants.

DESIGN

Population based observational study.

SETTING

We did a nested case-control analysis within a new user cohort formed using the United Kingdom General Practice Research Database.

PARTICIPANTS

New users of venlafaxine, fluoxetine, citalopram, or dosulepin on or after 1 January 1995, aged 18 to 89 years, with a diagnosis of depression or anxiety. Participants were followed-up until February 2005, or the occurrence of sudden cardiac death or near death, identified from medical records indicating non-fatal acute ventricular tachyarrhythmia, sudden death due to cardiac causes, or out of hospital deaths from acute ischaemic cardiac events. For each case, 30 controls were selected matched for age, sex, calendar time, and indication. We used conditional logistic regression to calculate the adjusted odds ratio of sudden cardiac death or near death associated with current use of venlafaxine compared with current use of fluoxetine, citalopram or dosulepin.

RESULTS

207 384 participants were followed-up for an average of 3.3 years. There were 568 cases of sudden cardiac death or near death, which were matched to 14 812 controls. The adjusted odds ratio of sudden cardiac death or near death associated with venlafaxine use was 0.66 (95% confidence interval 0.38 to 1.14) relative to fluoxetine use, whereas compared with citalopram it was 0.89 (0.50 to 1.60) and with dosulepin 0.83 (0.46 to 1.52).

CONCLUSIONS

In this large, population based study, the use of venlafaxine was not associated with an excess risk of sudden cardiac death or near death compared with fluoxetine, dosulepin, or citalopram, in patients with depression or anxiety.

Use of a claims-based active drug safety surveillance system to assess the risk of acute pancreatitis with exenatide or sitagliptin compared to metformin or glyburide

OBJECTIVE

To estimate risk and relative risk (RR) of acute pancreatitis among patients using incretin-based diabetes therapies (exenatide or sitagliptin) compared to patients treated with agents with established safety profiles (metformin or glyburide).

RESEARCH DESIGN AND METHODS

The study population was derived from a large US commercial health insurance transaction database using an active drug safety surveillance system (i3 Aperio). This analysis is based on data from June 2005 through June 2008. Cohorts of exenatide and sitagliptin initiators were each matched to an equal number of metformin or glyburide (met/gly) initiators using propensity scores to reduce confounding in the comparison of outcomes during follow-up. Patients with claims suggesting pancreatic disease in the 6 months prior to cohort entry were excluded.

MAIN OUTCOME MEASURE

Claims for hospitalizations associated with a primary diagnosis of acute pancreatitis (ICD-9 577.0).

RESULTS

There were 27 996 exenatide initiators and 16 276 sitagliptin initiators and approximately equal numbers of matched comparators. During follow-up of up to 1 year, acute pancreatitis occurred among 0.13% of patients treated with exenatide and 0.12% of patients treated with sitagliptin. The risk of acute pancreatitis was comparable for initiators of exenatide (RR 1.0; 95% confidence interval (CI) 0.6-1.7) and sitagliptin (RR 1.0; 95% CI 0.5-2.0) relative to the comparison cohorts.

CONCLUSIONS

These data do not provide evidence for an association of acute pancreatitis among initiators of exenatide or sitagliptin compared to met/gly initiators. These results are limited by the data available in an administrative, healthcare database.

Diagnostic codes for sudden cardiac death and ventricular arrhythmia functioned poorly to identify outpatient events in EPIC's General Practice Research Database

PURPOSE

To examine the validity of OXMIS/Read diagnoses of hospitalization for sudden cardiac death and ventricular arrhythmia (SD/VA) for use in studies of arrhythmogenic effects of outpatient medications in the General Practice Research Database (GPRD).

METHODS

We identified putative occurrences of hospitalization for SD/VA in patients receiving outpatient prescriptions for cisapride, domperidone, or metoclopramide. We then administered a questionnaire to general practitioners (GPs) caring for these patients, requested hospital discharge consult letters, and examined the positive predictive value (PPV) of diagnostic codes in identifying outpatient events precipitating hospitalization.

RESULTS

We identified 84 putative events, 38 (45%) of which occurred in patients cared for by GPs participating in the follow-up scheme. Thirty of 38 questionnaires (79%) were completed. The PPV for the occurrence of any SD/VA was 93% (95% CI, 78-99%). However, the PPV for SD/VA occurrence in an outpatient setting precipitating a hospitalization was only 23% (95% CI, 10-42%). The majority of inpatient diagnostic codes reflected events occurring after hospital admission, not precipitating it.

CONCLUSIONS

While computerized codes for SD/VA agreed well with physician diagnosis, they operated poorly to identify events occurring in an outpatient setting. Studies of SD/VA in the GPRD should verify events on a case-by-case basis.

Cisapride and ventricular arrhythmia

AIMS

We aimed to examine the association between cisapride and ventricular arrhythmia, and examine the relationship to dose and CYP3A4 inhibitors.

METHODS

A nested case-control study was conducted in Medicaid beneficiaries exposed to cisapride, metoclopramide or a proton pump inhibitor (PPI) from 1999 to 2000. Cases were hospitalized with a principal International Classification of Diseases-9 code indicating sudden cardiac death or ventricular arrhythmia. Controls had at least as much event-free person time following the study prescription as its matched case.

RESULTS

A total of 145 cases and 7250 controls were identified. The unadjusted rate ratio for cisapride vs. PPIs was 1.49 (95% confidence interval 0.96, 2.25). The adjusted odds ratio (OR) for cisapride vs. PPIs was 2.10 (1.34, 3.28). Excluding persons in managed care, the adjusted OR for cisapride was 2.92 (1.55, 5.49). In the initial prescription period, the adjusted OR for cisapride vs. PPIs was 7.85 (1.95, 31.60). Non-arrhythmogenic CYP3A4 inhibitors were not associated with an increased risk in users of cisapride or PPI inhibitors. The OR for potentially arrhythmogenic CYP3A4 inhibitors was 3.79 (1.76, 8.15) in cisapride users and 3.47 (2.06, 5.83) in PPI users.

CONCLUSIONS

Cisapride was associated with a doubling to tripling of the risk of hospitalization for ventricular arrhythmia, and a nearly eightfold risk in the initial prescription period. Although use of potentially arrhythmogenic CYP3A4 inhibitors was associated with an increased risk, this appears to be due to a direct effect of the drugs themselves rather than an interaction with cisapride.

Moving towards better predictors of drug-induced torsades de pointes

Drug-induced torsades de pointes (TdP) remains a significant public health concern that has challenged scientists who have the responsibility of advancing new medicines through development to the patient, while assuring public safety. As a result, from the point of discovering a new molecule to the time of its registration, significant efforts are made to recognize potential liabilities, including the potential for TdP. With this background, the ILSI (HESI) Proarrhythmia Models Project Committee recognized that there was little practical understanding of the relationship between drug effects on cardiac ventricular repolarization and the rare clinical event of TdP. A workshop was therefore convened at which four topics were considered including: Molecular and Cellular Biology Underlying TdP, Dynamics of Periodicity, Models of TdP Proarrhythmia and Key Considerations for Demonstrating Utility of Pre-Clinical Models. The series of publications in this special edition has established the background, areas of debate and those that deserve scientific pursuit. This is intented to encourage the research community to contribute to these important areas of investigation in advancing the science and our understanding of drug-induced proarrhythmia.

International Life Sciences Institute (Health and Environmental Sciences Institute, HESI) initiative on moving towards better predictors of drug-induced torsades de pointes

Knowledge of the cardiac safety of emerging new drugs is an important aspect of assuring the expeditious advancement of the best candidates targeted at unmet medical needs while also assuring the safety of clinical trial subjects or patients. Present methodologies for assessing drug-induced torsades de pointes (TdP) are woefully inadequate in terms of their specificity to select pharmaceutical agents, which are human arrhythmia toxicants. Thus, the critical challenge in the pharmaceutical industry today is to identify experimental models, composite strategies, or biomarkers of cardiac risk that can distinguish a drug, which prolongs cardiac ventricular repolarization, but is not proarrhythmic, from one that prolongs the QT interval and leads to TdP. To that end, the HESI Proarrhythmia Models Project Committee recognized that there was little practical understanding of the relationship between drug effects on cardiac ventricular repolarization and the rare clinical event of TdP. It was on that basis that a workshop was convened in Virginia, USA at which four topics were introduced by invited subject matter experts in the following fields: Molecular and Cellular Biology Underlying TdP, Dynamics of Periodicity, Models of TdP Proarrhythmia, and Key Considerations for Demonstrating Utility of Pre-Clinical Models. Contained in this special issue of the British Journal of Pharmacology are reports from each of the presenters that set out the background and key areas of discussion in each of these topic areas. Based on this information, the scientific community is encouraged to consider the ideas advanced in this workshop and to contribute to these important areas of investigations over the next several years.

Key clinical considerations for demonstrating the utility of preclinical models to predict clinical drug-induced torsades de pointes

While the QT/QTc interval is currently the best available clinical surrogate for the development of drug-induced torsades de pointes, it is overall an imperfect biomarker. In addition to low specificity for predicting arrhythmias, other issues relevant to using QT as a biomarker include (1) an apparent dissociation, for some drugs (for example, amiodarone, sodium pentobarbital, ranolazine) between QT/QTc interval prolongation and TdP risk, (2) Lack of clarity regarding what determines the relationship between QTc prolongation and TdP risk for an individual drug, (3) QT measurement issues, including effects of heart rate and autonomic perturbations, (4) the significant circadian changes to the QT/QTc interval and (5) concerns that the development, regulatory and commercial implications of finding even a mild QT prolongation effect during clinical development has significant impact the pharmaceutical discovery pipeline. These issues would be significantly reduced, clinical development simplified and marketing approval for some drugs might be accelerated if there were a battery of preclinical tests that could reliably predict a drug's propensity to cause TdP in humans, even in the presence of QTc interval prolongation. This approach is challenging and for it to be acceptable to pharmaceutical developers, the scientific community and regulators, it would need to be scientifically well validated. A very high-negative predictive value demonstrated in a wide range of drugs with different ionic effects would be critical. This manuscript explores the issues surrounding the use of QT as a clinical biomarker and potential approaches for validating preclinical assays for this purpose against clinical data sets.

Prokinetic therapy for feed intolerance in critical illness: one drug or two?

OBJECTIVE

To compare the efficacy of combination therapy, with erythromycin and metoclopramide, to erythromycin alone in the treatment of feed intolerance in critically ill patients.

DESIGN

Randomized, controlled, double-blind trial.

SETTING

Mixed medical and surgical intensive care unit.

PATIENTS

Seventy-five mechanically ventilated, medical patients with feed intolerance (gastric residual volume > or =250 mL).

INTERVENTIONS

Patients received either combination therapy (n = 37; 200 mg of intravenous erythromycin twice daily + 10 mg of intravenous metoclopramide four times daily) or erythromycin alone (n = 38; 200 mg of intravenous erythromycin twice daily) in a prospective, randomized fashion. Gastric feeding was re-commenced and 6-hourly gastric aspirates performed. Patients were studied for 7 days. Successful feeding was defined as a gastric residual volume <250 mL with the feeding rate > or =40 mL/hr, over 7 days. Secondary outcomes included daily caloric intake, vomiting, postpyloric feeding, length of stay, and mortality.

MEASUREMENTS AND MAIN RESULTS

Demographic data; use of inotropes, opioids, or benzodiazepines; and pretreatment gastric residual volume were similar between the two groups. The gastric residual volume was significantly lower after 24 hrs of treatment with combination therapy, compared with erythromycin alone (136 +/- 23 mL vs. 293 +/- 45 mL, p = .04). Over the 7 days, patients treated with combination therapy had greater feeding success, received more daily calories, and had a lower requirement for postpyloric feeding, compared with erythromycin alone. Tachyphylaxis occurred in both groups but was less with combination therapy. Sedation, higher pretreatment gastric residual volume, and hypoalbuminemia were significantly associated with a poor response. There was no difference in the length of hospital stay or mortality rate between the groups. Watery diarrhea was more common with combination therapy (20 of 37 vs. 10 of 38, p = .01) but was not associated with enteric infections, including Clostridium difficile.

CONCLUSIONS

In critically ill patients with feed intolerance, combination therapy with erythromycin and metoclopramide is more effective than erythromycin alone in improving the delivery of nasogastric nutrition and should be considered as the first-line treatment.

Risk of Clostridium difficile diarrhoea in critically ill patients treated with erythromycin-based prokinetic therapy for feed intolerance

OBJECTIVE

To determine the incidence of Clostridium difficile (CD) diarrhoea in feed-intolerant, critically ill patients who received erythromycin-based prokinetic therapy.

DESIGN AND SETTING

Prospective observational study in a mixed intensive care unit.

METHODS

The development of diarrhoea (> 3 loose, liquid stool per day with an estimated total volume > or = 250ml/day) was assessed in 180 consecutive critically ill patients who received prokinetic therapy (erythromycin only, n = 53; metoclopramide, n 37; combination erythromycin/metoclopramide, n = 90) for feed intolerance. Stool microscopy, culture and CD toxin assay were performed in all patients who developed diarrhoea during and after prokinetic therapy. Diarrhoea was deemed to be related to CD infection if CD toxin was detected.

RESULTS

Demographics, antibiotic use and admission diagnosis were similar amongst the three patients groups. Diarrhoea developed in 72 (40%) patients, 9.9 +/- 0.8 days after commencement of therapy, none of whom was positive for CD toxin or bacterial infection. Parasitic infections were found in four aboriginal men from an area endemic for these infections. Diarrhoea was most prevalent in patients who received combination therapy (49%) and was more common than in those who received erythromycin alone (30%) and metoclopramide alone (32%). Diarrhoea was short-lasting with a mean duration of 3.6 +/- 1.2 days.

CONCLUSIONS

In critical illness, diarrhoea following the administration of erythromycin at prokinetic doses is not associated with CD but may be related to pro-motility effects of the agent. Prokinetic therapy should be stopped at the onset of diarrhoea and prophylactic use should be strictly avoided.

Risk of Clostridium difficile diarrhoea in critically ill patients treated with erythromycin-based prokinetic therapy for feed intolerance

OBJECTIVE

To determine the incidence of Clostridium difficile (CD) diarrhoea in feed-intolerant, critically ill patients who received erythromycin-based prokinetic therapy.

DESIGN AND SETTING

Prospective observational study in a mixed intensive care unit.

METHODS

The development of diarrhoea (> 3 loose, liquid stool per day with an estimated total volume > or = 250ml/day) was assessed in 180 consecutive critically ill patients who received prokinetic therapy (erythromycin only, n = 53; metoclopramide, n 37; combination erythromycin/metoclopramide, n = 90) for feed intolerance. Stool microscopy, culture and CD toxin assay were performed in all patients who developed diarrhoea during and after prokinetic therapy. Diarrhoea was deemed to be related to CD infection if CD toxin was detected.

RESULTS

Demographics, antibiotic use and admission diagnosis were similar amongst the three patients groups. Diarrhoea developed in 72 (40%) patients, 9.9 +/- 0.8 days after commencement of therapy, none of whom was positive for CD toxin or bacterial infection. Parasitic infections were found in four aboriginal men from an area endemic for these infections. Diarrhoea was most prevalent in patients who received combination therapy (49%) and was more common than in those who received erythromycin alone (30%) and metoclopramide alone (32%). Diarrhoea was short-lasting with a mean duration of 3.6 +/- 1.2 days.

CONCLUSIONS

In critical illness, diarrhoea following the administration of erythromycin at prokinetic doses is not associated with CD but may be related to pro-motility effects of the agent. Prokinetic therapy should be stopped at the onset of diarrhoea and prophylactic use should be strictly avoided.

The Incidence of First Provoked and Unprovoked Seizure in Pediatric Patients with and without Psychiatric Diagnoses

PURPOSE

To estimate the rate of new-onset afebrile provoked and unprovoked seizure in a general pediatric population and subgroups of patients with and without psychiatric diagnoses other than attention deficit hyperactivity disorder (ADHD).

METHODS

A retrospective cohort study of 133,440 pediatric patients, between the ages of 6 and 17 years, and without history of seizure or prior use of anticonvulsant medications, with follow-up during 2003. The data source for this study was Ingenix's research database containing pharmacy and medical claims for members of a large US-based managed care organization. The main outcome measure was new-onset nonfebrile seizure. Incidence rates of seizure and 95% confidence intervals (CI) were calculated and expressed as rates per 100,000 person-years.

RESULTS

There were 132 new-onset provoked and unprovoked seizures in 78,423 person-years of follow-up among the general pediatric population sample. The incidence rate of seizure among the general pediatric population was 168 per 100,000 p-y (95% CI 141-200). The incidence rate of seizure among patients without psychiatric diagnoses was 149 per 100,000 p-y (95% CI 122-180). The incidence rate of seizure among patients with psychiatric diagnoses other than ADHD was 513 per 100,000 p-y (95% CI 273-878). There were increases in the incidence rates of seizure in all of the seizure risk factor groups, but this was more pronounced among males ages 6-12 with psychiatric diagnoses.

CONCLUSIONS

The results of this study are consistent with previous reports showing that pediatric patients with psychiatric disorders have a higher incidence rate of seizure than the general pediatric population.

Increase in mortality rate following coprescription of cisapride and contraindicated drugs

BACKGROUND

No epidemiologic study, as of this writing, has been published on the use of cisapride with contraindicated drugs and its relation to mortality rates in a population-based setting.

OBJECTIVE

To estimate the prevalence of concomitant use of cisapride with contraindicated drugs and evaluate the association between this and the risk of mortality.

METHODS

Claims data were obtained from the Health Insurance Review Agency of Korea. The study population consisted of patients younger than 85 years who visited clinics or hospitals in the city of Busan as new users of cisapride between November 1, 2000, and April 30, 2002. The coprescription of cisapride was defined as prescribing cisapride with one or more contraindicated drugs with the same prescription. Nationwide mortality data were also used. The prevalence of coprescribing cisapride was estimated and the association between this and the risk of mortality was assessed by rate ratios (RRs). The RRs were estimated using Cox's regression model with time-dependent covariate, adjusted for age, sex, and comorbidities.

RESULTS

A total of 36,865 patients out of 56,012 claims were newly prescribed cisapride; of these, 1175 patients (3.2%) were concomitantly prescribed at least one contraindicated drug, which suggested adjusted mortality RRs of 14.08 (95% CI 7.41 to 26.76) for recent users and 1.33 (95% CI 0.92 to 1.93) for past users of cisapride.

CONCLUSIONS

Despite the discontinuation of the drug's commercial marketing, cisapride was still in use in clinics and hospitals in Busan. In many cases, cisapride was co-prescribed with contraindicated drugs, which is associated with increased mortality rates.

Erythromycin is more effective than metoclopramide in the treatment of feed intolerance in critical illness

OBJECTIVE

This study aimed to a) compare the efficacy of metoclopramide and erythromycin in the treatment of feed intolerance in critical illness; and b) determine the effectiveness of "rescue" combination therapy in patients who fail monotherapy.

DESIGN

Randomized controlled trial.

SETTING

Level III mixed medical and surgical intensive care unit.

PATIENTS

Ninety mechanically ventilated, medical patients with feed-intolerance (gastric residual volume>or=250 mL).

INTERVENTIONS

Patients received either metoclopramide 10 mg intravenously four times daily (n=45) or erythromycin 200 mg intravenously twice a day (n=45) in a double-blind, randomized fashion. After the first dose, nasogastric feeding was commenced and 6-hourly nasogastric aspirates were performed. If a gastric residual volume>or=250 mL recurred on treatment, open-label, combination therapy was given. Patients were studied for 7 days. Successful feeding was defined as 6-hourly gastric residual volume<250 mL with a feeding rate>or=40 mL/hr.

MEASUREMENTS AND MAIN RESULTS

Demographic data, blood glucose levels, and use of inotropes, opioids, and benzodiazepines were similar between the two groups. After 24 hrs of treatment, both monotherapies reduced the mean gastric residual volume (metoclopramide, 830+/-32 mL to 435+/-30 mL, p<.0001; erythromycin, 798+/-33 mL to 201+/-19 mL, p<.0001) and improved the proportion of patients with successful feeding (metoclopramide=62% and erythromycin=87%). Treatment with erythromycin was more effective than metoclopramide, but the effectiveness of both treatments declined rapidly over time. In patients who failed monotherapy, rescue combination therapy was highly effective (day 1=92%) and maintained its effectiveness for the study duration (day 6=67%). High pretreatment gastric residual volume was associated with poor response to prokinetic therapy.

CONCLUSIONS

In critical illness, erythromycin is more effective than metoclopramide in treating feed intolerance, but the rapid decline in effectiveness renders both treatments suboptimal. Rescue combination therapy is highly effective, and further study is required to examine its role as the first-line therapy.

Application of the Bradford Hill Criteria to Assess the Causality of Cisapride-Induced Arrhythmia

INTRODUCTION

The Bradford Hill criteria are a widely used, useful tool for the assessment of biomedical causation. We have examined their application to pharmacovigilance using the example of cisapride-induced QTc interval prolongation/arrhythmia.

METHODS

A literature search was conducted using MEDLINE, EMBASE, Reactions Weekly and regulatory websites to identify evidence for the association between cisapride and QTc interval prolongation/arrhythmia that had been published in the English language. Two hundred and five publications were identified as being potentially suitable for the study. After excluding irrelevant articles, studies on high-risk populations and review articles, 70 publications were assessed using the Bradford Hill criteria. These included 24 case reports, case series or spontaneous report summaries; eight epidemiological studies; 22 clinical studies; and 16 experimental (in vivo and in vitro) publications.

RESULTS

The most compelling evidence for an association between cisapride use and QTc interval prolongation/arrhythmia came from case/spontaneous reports and biological plausibility. Considering the rare incidence of serious cardiac events, these criteria formed the basis for the strength of the association. The number of reports from different populations showed consistency. Specificity was supported by clinical and cardiographic characterisation of the events. There were temporal relationships between the events and the initiation of cisapride treatment, increases in the dosage and the receipt of interacting medications. The relationships between the adverse events and the latter two factors exhibited biological gradients. Experimental evidence could be found from biological models, as well as reports of positive dechallenge and/or rechallenge found in individual patients. Cisapride was found to bind the human ether-a-go-go-related gene (HERG) potassium channel, which provides a plausible mechanism for QTc interval prolongation/arrhythmia. Other QTc interval-prolonging/arrhythmic drugs that also bind to HERG provided an analogy for cisapride causing QTc interval prolongation/arrhythmia via this mechanism. The evidence provided by clinical studies was inconsistent, and epidemiological studies failed to demonstrate an association. Nevertheless, this did not prevent the assessment of causation.

DISCUSSION

This study showed how different types of evidence found in pharmacovigilance can be evaluated using the Bradford Hill criteria. Further work is required to examine how the criteria can be applied to different types of adverse events and how they may be applied to pharmacovigilance.

Clinical evaluation of QT/QTc prolongation and proarrhythmic potential for nonantiarrhythmic drugs: the International Conference on Harmonization of Technical Requirements for Registration of Pharmaceuticals for Human Use E14 guideline

Proarrhythmias due to drug-induced QT prolongation are the second most common cause for drug withdrawal and have caused increasing concern. Two new International Conference on Harmonization of Technical Requirements for Registration of Pharmaceuticals for Human Use (ICH) guidelines were recently endorsed in which nonclinical (S7B) and clinical (E14) methodologies are discussed and guidance is given to the industry. This commentary describes the key components of the E14 document, the impact of nonclinical testing on the clinical program, the thorough QT study, and the impact of its result on late-stage development. The studies described in S7B and E14 will contribute to a better understanding of the link between nonclinical assays and QT prolongation in humans. Differences in interpretation among individual regulators in the major regions with respect to measures proposed in the E14 guideline might impact regional regulatory decisions. These differences include the value of nonclinical assays for the subsequent clinical testing and how predictive a negative thorough QT study result is for proarrhythmic risk in patients.

In-hospital cardiac arrest is associated with use of non-antiarrhythmic QTc-prolonging drugs

AIMS

QTc interval-prolonging drugs have been linked to cardiac arrhythmias, cardiac arrest and sudden death. In this study we aimed to quantify the risk of cardiac arrest associated with the use of non-antiarrhythmic QTc-prolonging drugs in an academic hospital setting.

METHODS

We performed a case-control study in which patients, for whom intervention of the advanced life support resuscitation team was requested for cardiac arrest between 1995 and 2003 in the Academic Medical Centre, Amsterdam, were compared with controls regarding current use of non-antiarrhythmic QTc-prolonging drugs. Odds ratios (OR) and 95% confidence intervals (CI) were calculated using unconditional logistic regression, adjusting for potential confounding factors.

RESULTS

A statistically significant increased risk of cardiac arrest (OR 2.1, 95% CI 1.2, 3.5) was observed in patients who received QTc-prolonging drugs (42/140). The risk was more pronounced in patients receiving doses > 1 defined daily dose (OR 2.5, 95% CI 1.1, 5.9), patients taking > 1 QTc-prolonging drug simultaneously (OR 4.8, 95% CI 1.6, 14) and patients taking pharmacokinetic interacting drugs concomitantly (OR 4.0, 95% CI 1.2, 13).

CONCLUSIONS

Use of non-antiarrhythmic QTc-prolonging drugs in hospitalized patients with several underlying disease is associated with an increased risk of cardiac arrest. The effect is dose related and pharmacokinetic drug-drug interactions increase the risk substantially. Physicians caring for inpatients should be made aware of the fact that these non-antiarrhythmic drugs may be hazardous, so that potential risks can be weighed against treatment benefits and additional cardiac surveillance can be requested, if necessary.

Risk factors for prolonged QTc among US adults: Third National Health and Nutrition Examination Survey

BACKGROUND

QT interval prolongation can lead to torsades de pointes, a potentially fatal arrhythmia. Although research exists on the relationship between QT prolongation and clinical outcome, few studies have described risk factors for prolonged QT interval in the general population.

METHODS

The Third National Health and Nutrition Examination Survey (NHANES III) collected electrocardiogram interval data on 8561 subjects over 40 years of age and projected results to the US population. QT was corrected for heart rate using Fridericia's formula. Logistic regression analyses were performed to identify factors independently associated with prolonged QTc interval, defined as being in the upper 5% of the population QTc interval distribution. Analyses were conducted separately for women and men as a result of differences in the QT distribution between the sexes and also because of potential effect modification. Analytical variables included age, race/ethnicity, electrolyte measurements, body mass index, the recent use of QT-prolonging drugs and past medical histories of stroke, thyroid disease, hypertension, diabetes and myocardial infarction.

RESULTS

Age, female sex, hypocalcemia (men), hypokalemia (women), and a history of thyroid disease and myocardial infarction (men) were associated with a prolonged QTc interval. In addition, taking QT-prolonging medications in the past month was associated with more than a twofold increase in the odds of prolonged QTc interval in both men and women.

CONCLUSIONS

Healthcare practitioners should be aware that a prolonged QTc interval is a potential indicator of cardiovascular risk, and should exercise caution in prescribing potentially QT-prolonging medications to certain patients.

Use of arterially perfused rabbit ventricular wedge in predicting arrhythmogenic potentials of drugs

INTRODUCTION

A growing number of drugs have reportedly been associated with delayed ventricular repolarization and a potentially fatal but rare arrhythmia, torsade de pointes (TdP). There is obviously a call for a validated proarrhythmia model that distinguishes proarrhythmic drugs from nonarrhythmogenic drugs.

METHODS

In this article, we validated the arterially perfused rabbit left ventricular wedge preparation model and examined its use in predicting proarrhythmic potentials of drugs. A fairly detailed methodological description about this technically challenging model was given, aiming to help others establish the assay successfully. Parameters commonly used in the action potential studies were verified and critical experimental conditions (e.g. stability and reproducibility of recordings) were examined. Six commercially available compounds with various proarrhythmic potentials were administered in the model to evaluate their correlations with individual clinical outcomes.

RESULTS

Our study indicated that, in a successful experiment, the action potential duration (APD) can be stably maintained for several hours without intervention. Dofetilide, DL-sotalol, cisapride, risperidone and moxifloxacin increased endo- and epicardial APD(90), QT interval and T(P-E) (peak-to-end time of the T wave) in a reverse use-dependent manner within clinically relevant concentration ranges. Phase 2 early afterdepolarizations (EADs) were observed at 1.6, 2.3, 16.7, 37.5 and 7.9 fold, respectively, their corresponding unbound therapeutic concentrations. In contrast, fluoxetine at up to 3 microM (approximately 35 fold unbound therapeutic mean plasma concentration after 60 mg/day, p.o. for 5 weeks) had only a mild prolonging effect on APD(90) and QT with essentially no effect on T(P-E).

DISCUSSION

Our results strongly support the usefulness of this model in predicting a compound's arrhythmogenic potential in humans within clinically relevant concentration ranges, and the experimental results with this model need to be interpreted in light of each drug's pharmacokinetic and pharmacodynamic behavior in clinic.

Co-dispensing of contraindicated medications in patients using cisapride in Italy

PURPOSE

To investigate the co-dispensing of contraindicated medications in patients using cisapride in an Italian population.

METHODS

The study included patients who had at least one cisapride prescription dispensed between 1 April 1997 and 30 September 2000. The proportion of cisapride users with concomitant medications, the proportion of prescriptions of cisapride with an overlapping dispensing of a contraindicated medication and the proportion of person-days of cisapride use concomitant with contraindicated medications, were calculated.

RESULTS

In the 4-year study period, 249,740 total cisapride prescriptions, which corresponded to 382,835 packages, were dispensed to 91,204 users (52,442 female, 57.5%). Concomitant use of contraindicated drugs was identified in 4403 cisapride users (4.83%). Throughout the study period, there was an increase in the proportion of cisapride users with contraindicated co-prescriptions: 4.29% in 1997, 4.99% in 1998, 5.15% in 1999, but a decline to 3.34% in 2000. In each year, this figure was higher in males, with the highest proportion reported in 1999 (5.50%). A total of 7215 cisapride prescriptions (2.85%) were concomitant with contraindicated drugs, ranging from 2.27% in September 1998 to 3.55% in January 1999. Cisapride prescriptions were most frequently associated with macrolide antibiotics (1.14%) and class III antiarrhythmics (1.03%).

CONCLUSIONS

In the period 1997-2000, a substantial proportion of cisapride prescriptions were concomitant with contraindicated medications. In Italy in 1998, the National Health Authority issued a bulletin warning about the risk of serious arrhythmias after concomitant use of contraindicated drugs. Despite this warning, there was no reduction in contraindicated drug uses.

Usage of the claim database of national health insurance programme for analysis of cisapride-erythromycin co-medication in Taiwan

PURPOSE

This study aimed to use the National Health Insurance Research Database, Taiwan for risk analysis of concomitant use of cisapride and erythromycin.

METHODS

The sample consisted of subjects identified in the Outpatient Sampling Database (OSD) and Longitudinal Health Insurance Database 2000 (LHID 2000), derived from the original claim data of the National Health Insurance Research Database, Taiwan.

RESULTS

According to the LHID 2000, a total of 464 individuals experienced 685 episodes of cisapride-erythromycin co-medication prescribed by 295 physicians, revealing a prevalence of 4.5% concomitant use, with higher prevalence in clinics (9.2%) than in other medical institutes (3.7-5.4%). Among the co-medication episodes, 81.9% and 61.2% were prescribed from the same health institutes and by the same physicians, respectively. No medical record of cardiac arrhythmias was found among these patients in 2001 and 2002, probably due to the fact that 78.9% of the 464 individuals were under age 16, 84.0% had short exposure duration (1-4 days) and 98.0% of the episodes were prescribed with a cisapride dose of less than 0.8 mg/kg/day.

CONCLUSIONS

Findings from this study suggest that there exists an urgent need for accreditation in terms of pharmacovigilance of clinical sites and their practicing physicians for the prevention of irrational concomitant prescription in Taiwan. Our findings also indicate that it is necessary to investigate other possible conditions of potentially dangerous co-medication in Taiwan and other developing countries.

Structural determinants of potassium channel blockade and drug-induced arrhythmias

Cardiac K+ channels play an important role in the regulation of the shape and duration of the action potential. They have been recognized as targets for the actions of neurotransmitters, hormones, and anti-arrhythmic drugs that prolong the action potential duration (APD) and increase refractoriness. However, pharmacological therapy, often for the purpose of treating syndromes unrelated to cardiac disease, can also increase the vul- nerability of some patients to life-threatening rhythm disturbances. This may be due to an underlying propensity stemming from inherited mutations or polymorphisms, or structural abnormalities that provide a substrate allowing for the initiation of arrhythmic triggers. A number of pharmacological agents that have proved useful in the treatment of allergic reactions, gastrointestinal disorders, and psychotic disorders, among others, have been shown to reduce repolarizing K+ currents and prolong the Q-T interval on the electrocardiogram. Understanding the structural determinants of K+ channel blockade might provide new insights into the mechanism and rate-dependent effects of drugs on cellular physiology. Drug-induced disruption of cellular repolarization underlies electrocardiographic abnormalities that are diagnostic indicators of arrhythmia susceptibility.

Respiratory medications and the risk of cardiac arrhythmias

BACKGROUND

Medications used to treat respiratory diseases include beta-adrenoceptors, antimuscarinics, inhaled and oral corticosteroids, and theophyllines. Most of these drugs have been associated indirectly with cardiac rhythm disorders, but epidemiologic evidence is limited.

METHODS

To evaluate the association between respiratory drugs and the occurrence of rhythm disorders among patients with asthma and those with chronic obstructive pulmonary disease, we conducted a case-control study nested in a population-based cohort of individuals 10-79 years of age and registered in the U.K. General Practice Research Database after 1 January 1994. The analysis included 710 confirmed cases and 5000 controls frequency-matched to cases by age (interval of 1 year) and sex.

RESULTS

No increased risk of arrhythmias overall was found among users of inhaled steroids (relative risk = 1.0; 95% confidence interval = 0.8-1.3). Short-term use of theophylline was weakly associated with arrhythmia (1.8; 1.0-3.3). An increased risk was found among users of oral steroids, and the relative risk was greater at the beginning of therapy (2.6; 2.0-3.5). The risk of atrial fibrillation was increased, especially for short-term use of oral steroids (2.7; 1.9-3.8), and a weak association was seen for theophyllines, especially short-term use (1.8; 0.9-3.7). Supraventricular tachycardia was associated with long-term use of oral steroids (2.1; 0.8-5.7), long-term use of antimuscarinics (1.7; 0.7-4.1), and short-term use of theophylline (4.0; 0.9-18.1). Ventricular arrhythmias were associated with oral steroids (3.2; 0.8-13.3) and beta-adrenoceptors (7.1; 0.8-65.9).

CONCLUSIONS

Oral steroids and theophylline were the therapeutic groups associated with risk of developing atrial fibrillation, especially with new courses of therapy. Results from this study also are consistent with certain suspected dysrhythmic effects of theophyllines, with supraventricular tachycardia associated with antimuscarinics, and with ventricular arrhythmias associated with beta-adrenoceptors.

Non-cardiac QTc-prolonging drugs and the risk of sudden cardiac death

AIMS

To assess the association between the use of non-cardiac QTc-prolonging drugs and the risk of sudden cardiac death.

METHODS AND RESULTS

A population-based case-control study was performed in the Integrated Primary Care Information (IPCI) project, a longitudinal observational database with complete medical records from more than 500,000 persons. All deaths between 1 January 1995 and 1 September 2003 were reviewed. Sudden cardiac death was classified based on the time between onset of cardiovascular symptoms and death. For each case, up to 10 random controls were matched for age, gender, date of sudden death, and general practice. The exposure of interest was the use of non-cardiac QTc-prolonging drugs. Exposure at the index date was categorized into three mutually exclusive groups of current use, past use, and non-use. The study population comprised 775 cases of sudden cardiac death and 6297 matched controls. Current use of any non-cardiac QTc-prolonging drug was associated with a significantly increased risk of sudden cardiac death (adjusted OR: 2.7; 95% CI: 1.6-4.7). The risk of death was highest in women and in recent starters.

CONCLUSION

The use of non-cardiac QTc-prolonging drugs in a general population is associated with an increased risk of sudden cardiac death.

A prospective study of oesophageal 24-h ambulatory pH monitoring in patients with functional dyspepsia

BACKGROUND

The diagnostic utility of 24-h oesophageal ambulatory pH monitoring in patients with functional dyspepsia has not been well established.

AIMS

We performed a prospective study of oesophageal pH monitoring in patients with functional dyspepsia in order to assess whether a positive pH test might predict response to proton pump inhibitor therapy in a subset of functional dyspepsia patients.

PATIENTS

Forty Helicobacter pylori-negative functional dyspepsia patients (35 males and 5 females, mean age (+/-S.E.M.) of 54+/-2.4 years) with predominantly unspecified dyspepsia subtype and normal distal oesophageal biopsies.

METHODS

All subjects were randomised in a double-blind fashion to either omeprazole 20 mg/day or placebo daily for four weeks after 24-h pH monitoring.

RESULTS

Twenty-four-hour pH monitoring was abnormal in 9 of the 21 patients (43%) in the omeprazole group and 5/19 (26%) of the placebo group (p=NS). Patients who reported symptomatic improvement on the Gastrointestinal Symptom Rating Scale were no more likely to have abnormal scores on pH monitoring than patients who did not have symptomatic response.

CONCLUSIONS

Although approximately one-third of functional dyspepsia patients will have abnormal profiles on 24-h ambulatory oesophageal pH monitoring, an abnormal score does not appear to predict response to proton pump inhibitor therapy in patients with unspecified functional dyspepsia.

Comparative cardiac safety of low-dose thioridazine and low-dose haloperidol

AIM

To compare the rate of ventricular arrhythmia, sudden death and unexplained or unattended death among users of thioridazine and haloperidol.

METHODS

Observational cohort study of thioridazine and haloperidol users in the UK General Practice Research Database (GPRD) using data from 1987 through 29 June 2000. Patients were followed for 30 days following each study prescription. The event of interest was a diagnosis of ventricular arrhythmia, sudden death, or unexplained or unattended death. Cox regression was used to calculate rate ratios (RRs) and 95% confidence intervals (CIs), to examine potential confounding factors, and to examine dose-response relationships.

RESULTS

Use of thioridazine and haloperidol in the GPRD was primarily in older patients, at low dose (median daily dose 31 mg thioridazine, 1.8 mg haloperidol). There was no association between thioridazine use and the rate of ventricular arrhythmia, sudden death, and unexplained or unattended death (adjusted RR 0.9, 95% CI 0.7, 1.1). The rate did not appear to increase with dose for either drug over the range observed.

CONCLUSIONS

These results suggest that low-dose thioridazine and haloperidol have similar cardiac safety.

Prolongation of the QT interval and cardiac arrhythmias associated with cisapride: limitations of the pharmacoepidemiological studies conducted and proposals for the future

Not all hazards can be identified from clinical studies prior to marketing of medicinal products. Pre-marketing large-scale trials for cisapride did not report any serious cardiac arrhythmias. After a long period of availability in several countries it was withdrawn in 2000 because of reports of serious, and in many cases fatal, cardiac events. Whilst spontaneous reporting systems for adverse drug reactions (ADRs) have limitations such as under-reporting, they are an effective system for signal generation, particularly of rare ADRs. Pharmacoepidemiological studies aim to identify and calculate the incidence of adverse reactions, with increased sensitivity to less common ADRs compared to randomised controlled trials, yet cohort sizes may be insufficient to detect very rare ADRs such as drug-induced Torsade de Pointes, with an estimated incidence of the order of 1 per 12,000 to 1 per 120,000 patients. Several pharmacoepidemiological studies investigated adverse events associated with cisapride, one of which specifically examined the association between serious cardiac arrhythmias and cisapride. These observational studies were conducted using large population databases, but each failed to identify sufficient cases to establish a causal relationship. Explanations include that the cohort sample sizes were too small, and either under-, or mis-reporting of events of interest may have occurred. To estimate the risk of very rare adverse events, pharmacoepidemiological studies require very large numbers. Furthermore, the events in question need to be clinically recognisable by doctors and adequately documented in patients' notes, computer records, or on study questionnaires. The establishment of a national registry for drug-induced QT prolongation to identify cases and correlate clinical information may help to better identify these rare ADRs earlier. Such proactive surveillance could avoid unnecessary delays for other drugs where QT prolongation and serious cardiac arrhythmias may be an issue.

QTc-prolonging drugs and hospitalizations for cardiac arrhythmias

Cardiac arrhythmia as an adverse effect of noncardiac drugs has been an issue of growing importance during the past few years. In this population-based study, we evaluated the risk for serious cardiac arrhythmias during the use of several noncardiac QTc-prolonging drugs in day-to-day practice, and subsequently focused on several specific groups of patients who could be extremely vulnerable for drug-induced arrhythmias. We performed a case-control study in which patients (cases), hospitalized for nonatrial cardiac arrhythmias from 1987 to 1998, were compared with their matched controls regarding current use of QTc-prolonging drugs. Odds ratios (OR) and 95% confidence intervals (CI) were calculated using multivariate conditional logistic regression, adjusting for potential confounding factors. Data were obtained from the PHARMO record linkage system. We identified 501 cases, 39 of whom used QTc-prolonging drugs. A statistically nonsignificant increased risk for arrhythmias (OR 1.2, 95% CI 0.8 to 1.9) was observed in patients who received QTc-prolonging drugs. A clearly increased risk of arrhythmias was, however, found in patients with a history of asthma (OR 9.9, 95% CI 1.0 to 100) and in patients using potassium-lowering drugs (OR 5.3, 95% CI 1.1 to. 25.9). Our data do not suggest that there is a strong overall association between the use of QTc-prolonging drugs and hospitalization for cardiac arrhythmias in the population at large. However, there appears to be clinically relevant associations of patients with a history of asthma and patients taking potassium-lowering drugs. The use of QTc-prolonging drugs should therefore be either avoided or monitored closely in these specific patients.

Antipsychotic drugs and QT interval prolongation

The QTc prolongation by antipsychotic drugs is of major concern, especially in light of the data indicating an increased risk of sudden death in psychiatric patients taking these drugs. Sudden death in psychiatric patients could be partially attributed to drug-induced torsades de pointes and for this reason careful evaluation of QTc prolonging properties of antipsychotic drugs is needed. Antipsychotic drugs prolong QT interval usually by blocking the potassium IKr current. Improved understanding of ion channel structure and kinetics and its role in repolarization has tremendous impact on understanding of the mechanisms of drug-induced QT prolongation and torsades de pointes. Proarrhythmia caused by a QT-prolonging drug occurs infrequently, and usually multiple factors need to operate to precipitate such an event including a combination of two or more drugs affecting the same pathway, hypokalemia, and possibly genetic predisposition. Currently prescribed antipsychotics might cause QT prolongation ranging from 4-6 ms for haloperidol and olanzapine to 35 ms for thioridazine. The response of a patient to a drug is very individual and therefore an individualized system of drug administration and monitoring needs to be developed which takes into account baseline QTc duration and its changes after a drug was introduced. A systematic approach while stratifying psychiatric patients as those with short QTc (QTc < or = 0.41 sec), borderline QTc (QTC = 0.42-0.44 sec), and prolonged QTc (0.45 sec) is being proposed to improve the safety of administering antipsychotic drugs and to decrease the risk of drug-related sudden death in psychiatric patients.

Pharmacotherapy of gastro-oesophageal reflux disease in children: focus on safety

Gastro-oesophageal reflux (GOR) disease is very common and, in the majority of infants, is physiological. However, untreated GOR disease in infants and children is associated with a decrease in quality of life for the child and their parents. It may also cause sometimes more severe complications, such as oesophagitis, and causing, in rare cases, failure to thrive, oesophageal stricture, apnoea and even death. Every therapeutic intervention (non-drug treatment, medical treatment and surgery) is associated with morbidity and even mortality. Moreover, efficacy data of many medications in children are non-existing, limited or disappointing. The safety profile of cisapride is comparable to that of other therapeutic interventions or to the risk of non-treatment. Therefore, the therapeutic approach of GOR disease in infants and children needs to be well-balanced, considering therapeutic efficacy and side effects. This review will focus on the side effects of the different therapeutic options.