Syncopal episodes associated with cisapride and concurrent drugs

Iatrogenic neurology

Iatrogenic disease is one of the most frequent causes of hospital admissions and constitutes a growing public health problem. The most common type of iatrogenic neurologic disease is pharmacologic, and the central and peripheral nervous systems are particularly vulnerable. Despite this, iatrogenic disease is generally overlooked as a differential diagnosis among neurologic patients. The clinical picture of pharmacologically mediated iatrogenic neurologic disease can range from mild to fatal. Common and uncommon forms of drug toxicity are comprehensively addressed in this chapter. While the majority of neurologic adverse effects are listed and referenced in the tables, the most relevant issues are further discussed in the text.

Clarithromycin, QTc interval prolongation and torsades de pointes: the need to study case reports

BACKGROUND

The manufacturers of clarithromycin sought a drug similar in efficacy to erythromycin but with a superior side-effect profile. They generally achieved this outcome, but postmarketing findings identified a series of reports linking clarithromycin to QTc interval prolongation and torsades de pointes (TdP) ultimately leading to a Black Box Warning. We sought to clarify risk factors associated with TdP among case reports of patients receiving clarithromycin linked to QTc interval prolongation and TdP.

METHODS AND RESULTS

In a detailed literature search, we found 15 women, five men, and one boy meeting our search criteria. Among the 17 adults with reported clarithromycin dose and concurrent QTc interval measurement, we found no statistically significant relationship between clarithromycin dose and QTc interval duration. This did not change for the adults who developed TdP. Among adults, major risk factors were female sex (15), old age (11) and heart disease (17). A total of eight adult subjects had all three major risk factors and 14 of the 20 adults had at least two major risk factors. All adult subjects had at least two risk factors besides clarithromycin. A total of four of the 20 adults received cisapride and three received disopyramide. Three adults were considered to suffer from some aspect of the congenital long QT syndrome.

CONCLUSIONS

We believe that the risk factor description for this drug should be refined to emphasize the major risk factors of (1) female sex, (2) old age and (3) heart disease.

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.

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.

The differential antibacterial and gastrointestinal effects of erythromycin and its chiral isolates

The use of erythromycin has been limited by the gastrointestinal side effect properties, which include abdominal distress and diarrhea. To evaluate the possibility of reducing the toxicity of erythromycin, studies were undertaken to separate erythromycin into chiral isolates and then to test the activity of these chiral isolates on gastrointestinal contractility and bacteriostatic actions. Gastrointestinal contractility was obtained by the use of isolated strips of a rat colon. Antibacterial activity was used by obtaining the MICs of erythromycin and isolated agents against Enterococcus faecalis ATCC 29212. ANOVA was performed using the SPSS v.10 to determine statistical differences in the MICs and the amplitude and frequency of spike bursts. Results were expressed as mean+/-SE (N=5). The MICs (microg/mL) of erythromycin (racemate), chiral isolate X, and chiral isolate Y were 0.45+/-0.29, 0.53+/-0.24 (n.s.), and 0.2+/-0.07 (P<or=0.001), respectively. Erythromycin (racemate) at 10 mol/L, 10 mol/L, 5x10 mol/L, 10 mol/L, and 10 mol/L concentrations caused the amplitude of spike bursts to increase by 18+/-7% (P=n.s.), 43+/-10% (P<or=0.05), 55+/-12% (P<or=0.001), 121+/-23% (P<or=0.001), and 163+/-16% (P<or=0.001), respectively. The chiral isolate Y increased the amplitude of spike bursts at the same concentrations as tested above: 32+/-11% (P<or=0.05), 48+/-14% (P<or=0.001), 84+/-13% (P<or=0.001), 112+/-18% (P<or=0.001), and 121+/-13% (P<or=0.001), respectively. Chiral isolate X caused much reduced effect on the amplitude of spike bursts: 9+/-6% (P=n.s.), 27+/-12% (P=n.s.), 27+/-12% (P=n.s.), 30+/-11% (P=n.s.), and 30+/-11.2% (P=n.s.), respectively. EC50 for erythromycin (mixture) was 0.4x10 mol/L, and for erythromycin Y, it was 0.8x10 mol/L. The addition of erythromycin at 10 mol/L caused the frequency of spike bursts to increase 11+/-7% at 10 mol/L, 5x10 mol/L, 10 mol/L, and 10 mol/L; the changes were 13+/-10% (P=n.s.), 13+/-10% (P=n.s.), 22+/-13% (P=ns), and 39+/-30% (P<or=0.05), respectively. Chiral isolate Y of erythromycin, changed the frequency of spike bursts by 26+/-21% (P=n.s.); 35+/-20% (P=n.s.), 39+/-30% (P=n.s.), 41+/-37% (P=n.s.), and 44+/-36% (P=n.s.) at the respective concentrations as discussed above. Chiral isolate X altered the frequency of spike bursts at the same concentrations as 40+/-30% (P=n.s.), 45+/-30% (P=n.s.), 62+/-41% (P=n.s.), 62+/-41% (P=n.s.), and 52+/-35% (P=n.s.), respectively. Data indicate that erythromycin (racemate) and chiral isolates X and Y possess similar antibacterial activity. It was also shown that erythromycin and chiral isolate Y increase significantly the amplitude of spike bursts compared with baseline. Isolate X does not increase the amplitude of spike bursts in a dose-dependent manner. The frequency of spike bursts is not significantly changed in the presence of erythromycin or the 2 chiral isolates.

Inhibition of cytochrome P450 3A: relevant drug interactions in gastroenterology

Cytochrome P450 3A (CYP3A) is involved in biotransformation of more than half of all drugs currently available. Drug interactions by inhibition of CYP3A are of major interest in patients receiving combinations of drugs. Some interactions with CYP3A inhibitors also involve inhibition of the multidrug export pump, P-glycoprotein. An increasing number of adverse drug reactions might be avoided on the basis of knowledge about CYP3A substrates and inhibitors. This article summarizes some examples of such interactions relevant to gastroenterologists. Serious cases by coadministration of CYP3A inhibitors resulting in acute hepatitis, hypotension, rhabdomyolyis, torsade de pointes, sedation, or ergotism are presented: interactions with azole antifungals (ketoconazole, itraconazole, fluconazole), HIV protease inhibitors (ritonavir, indinavir, saquinavir, nelfinavir), macrolide antibiotics (clarithromycin, erythromycin), and grapefruit juice. In addition, 1 case is reported who presented the highest trough levels of the CYP3A substrate budesonide in serum ever measured. Practitioners have to be aware of the high potential of metabolic drug interactions when they prescribe a CYP3A inhibitor. It is wise to check carefully comedication in patients complaining of side effects with substrates of CYP3A.

Clarithromycin reducesIsusandItocurrents in human atrial myocytes with minor repercussions on action potential duration

The macrolide antibacterial agent clarithromycin has been shown to cause QT interval prolongation on the electrocardiogram. In rabbit heart preparations clarithromycin (concentration dependently) lengthened the action potential duration and blocked the delayed rectifier current. The aim of the present study was to investigate the clarithromycin effects: (i) on the Ca2+ L-type and the main K+ repolarizing currents on human atrial myocytes, using whole-cell patch clamp recordings and (ii) on action potentials recorded from human atrial and ventricular myocardium using conventional microelectrodes. It has been found that (i) 10-30 microM clarithromycin reduced the sustained current Isus significantly and that a 100 microM concentration was needed to cause a significant reduction in the transient outward current Ito, whereas clarithomycin did not affect the calcium current and (ii) clarithromycin (10-100 microM) prolonged the action potential duration in atrial preparations but did not alter the different parameters of the ventricular action potential. It is concluded that clarithromycin exerts direct cardiac electrophysiological effects that may contribute to pro-arrythmic potential.

Torsade de pointes due to noncardiac drugs: most patients have easily identifiable risk factors

Numerous medications, including drugs prescribed for noncardiac indications, can lead to QT prolongation and trigger torsade de pointes. Although this complication occurs only rarely, it may have lethal consequences. It is therefore important to know if patients with torsade de pointes associated with noncardiac drugs have risk factors that are easy to identify. We reviewed reports of drug-induced torsade de pointes and analyzed each case of torsade de pointes associated with a noncardiac drug for the presence of risk factors for the long QT syndrome that can be easily identified from the medical history or clinical evaluation (female gender, heart disease, electrolyte disturbances, excessive dosing, drug interactions, and history of familial long QT syndrome). We identified 249 patients with torsade de pointes caused by noncardiac drugs. The most commonly identified risk factor was female gender (71%). Other risk factors were frequently present (18%-41%). Virtually all patients had at least 1 of these risk factors, and 71% of patients had 2 or more risk factors. Our study suggests that almost all patients with torsade de pointes secondary to noncardiac drugs have risk factors that can be easily identified from the medical history before the initiation of therapy with the culprit drug.

Comparative effects of clarithromycin on action potential and ionic currents from rabbit isolated atrial and ventricular myocytes

Prolongation of QT interval by several antibacterial drugs is an unwanted side effect that may be associated with development of ventricular arrhythmias. The macrolide antibacterial agent clarithromycin has been shown to cause QT prolongation. To determine the electrophysiologic basis for this arrhythmogenic potential, we investigated clarithromycin effects on (i). action potentials recorded from rabbit Purkinje fibers and atrial and ventricular myocardium using conventional microelectrodes and (ii). potassium and calcium currents recorded from rabbit atrial and ventricular isolated myocytes using whole-cell patch clamp recordings. We found that (i). clarithromycin (3-100 microM) exerted concentration-dependent lengthening effects on action potential duration in all tissues, with higher efficacy and reverse frequency-dependence in Purkinje fibers. However, clarithromycin did not cause development of early afterdepolarizations, and the parameters other than action potential duration were almost unaffected; (ii). clarithromycin (10-100 microM) reduced the delayed rectifier current. Significant blockade (approximately 30%) was found at the concentration of 30 microM. At 100 microM, it decreased significantly the maximum peak of the calcium current amplitude but failed to alter the transient outward and inwardly rectifier currents. It was concluded that these effects might be an explanation for the QT prolongation observed in some patients treated with clarithromycin.

Drug interaction between mosapride and erythromycin without electrocardiographic changes

QT prolongation and torsades de pointes have been documented in patients administered cisapride and its blocking of potassium channels in myocytes has been suggested as the mechanism. An interaction with cytochrome P450 CYP3A4 inhibitor drugs like macrolide and azole antifungals is also thought to be a possible mechanism. Since mosapride has characteristics similar to cisapride, we examined the effects of mosapride on the electrocardiogram and pharmacokinetics before and after its coadministration with erythromycin. Ten healthy male volunteers were repeatedly administered mosapride 15 mg/day for 7 days followed by coadministration with erythromycin 1200 mg/day for 7 days. Coadministration with erythromycin resulted in a 1.6-fold increase in the Cmax of mosapride and prolongation of t(1/2) from 1.6 to 2.4 hours, indicating the inhibition of mosapride metabolism. However, there were no significant differences in the QT interval and QTc between mosapride alone and concomitant use with erythromycin. There was no correlation between the electrocardiographic parameters and plasma mosapride concentrations, and no case exceeded the upper limit of the normal range of QTc. Although there was a certain pharmacokinetic interaction between mosapride and erythromycin, their coadministration did not affect the electrocardiogram at all, indicating a reduced likelihood of severe clinical adverse events like QT prolongation and torsades de pointes.

Pharmacokinetic aspects of treating infections in the intensive care unit: focus on drug interactions

Pharmacokinetic interactions involving anti-infective drugs may be important in the intensive care unit (ICU). Although some interactions involve absorption or distribution, the most clinically relevant interactions during anti-infective treatment involve the elimination phase. Cytochrome P450 (CYP) 1A2, 2C9, 2C19, 2D6 and 3A4 are the major isoforms responsible for oxidative metabolism of drugs. Macrolides (especially troleandomycin and erythromycin versus CYP3A4), fluoroquinolones (especially enoxacin, ciprofloxacin and norfloxacin versus CYP1A2) and azole antifungals (especially fluconazole versus CYP2C9 and CYP2C19, and ketoconazole and itraconazole versus CYP3A4) are all inhibitors of CYP-mediated metabolism and may therefore be responsible for toxicity of other coadministered drugs by decreasing their clearance. On the other hand, rifampicin is a nonspecific inducer of CYP-mediated metabolism (especially of CYP2C9, CYP2C19 and CYP3A4) and may therefore cause therapeutic failure of other coadministered drugs by increasing their clearance. Drugs frequently used in the ICU that are at risk of clinically relevant pharrmacokinetic interactions with anti-infective agents include some benzodiazepines (especially midazolam and triazolam), immunosuppressive agents (cyclosporin, tacrolimus), antiasthmatic agents (theophylline), opioid analgesics (alfentanil), anticonvulsants (phenytoin, carbamazepine), calcium antagonists (verapamil, nifedipine, felodipine) and anticoagulants (warfarin). Some lipophilic anti-infective agents inhibit (clarithromycin, itraconazole) or induce (rifampicin) the transmembrane transporter P-glycoprotein, which promotes excretion from renal tubular and intestinal cells. This results in a decrease or increase, respectively, in the clearance of P-glycoprotein substrates at the renal level and an increase or decrease, respectively, of their oral bioavailability at the intestinal level. Hydrophilic anti-infective agents are often eliminated unchanged by renal glomerular filtration and tubular secretion, and are therefore involved in competition for excretion. Beta-lactams are known to compete with other drugs for renal tubular secretion mediated by the organic anion transport system, but this is frequently not of major concern, given their wide therapeutic index. However, there is a risk of nephrotoxicity and neurotoxicity with some cephalosporins and carbapenems. Therapeutic failure with these hydrophilic compounds may be due to haemodynamically active coadministered drugs, such as dopamine, dobutamine and furosemide, which increase their renal clearance by means of enhanced cardiac output and/or renal blood flow. Therefore, coadministration of some drugs should be avoided, or at least careful therapeutic drug monitoring should be performed when available. Monitoring may be especially helpful when there is some coexisting pathophysiological condition affecting drug disposition, for example malabsorption or marked instability of the systemic circulation or of renal or hepatic function.

Optimal management of patients with non-ulcer dyspepsia: considerations for the treatment of the elderly

Optimal therapy for patients with non-ulcer dyspepsia still remains elusive. Increasing consensus on the definition of non-ulcer dyspepsia may improve the design of clinical trials and result in more effective therapies for this common condition. This paper reviews the investigation, pathophysiology and therapy of non-ulcer dyspepsia in order to formulate management strategies in the elderly. The best outcome for the patient can be achieved by detailed evaluation, leading to therapy targeted to obvious precipitating factors such as dyspepsia-inducing medications and other aggravating factors such as slow-transit constipation. Prokinetics and, to a lesser extent, H(2) receptor antagonists are the main medications of choice. Cisapride, the best studied prokinetic, has been withdrawn from the market in certain countries because some patients experienced dangerous cardiac arrhythmias, especially when cisapride was given with potent inhibitors of cytochrome P450 3A4. Time spent on reassurance and judicious use of antidepressants for the right patient can help improve symptoms. In the elderly, however, persistent symptoms should be re-evaluated because of the increased incidence of malignancy.

Use of cisapride with contraindicated drugs in The Netherlands

OBJECTIVE

To investigate the prevalence of concomitant use and coprescribing of cisapride with potentially interacting drugs to evaluate the impact of these warnings from 1994 to 1998.

DESIGN

Retrospective follow-up study of patients using cisapride.

SETTING

Data for this study were obtained from the pharmacy database of the Dutch PHARMO record linkage system (n = 834,000).

RESULTS

From 1994 to 1998, the prevalence rate of the observed versus expected use of any potentially interacting drug decreased significantly over time (p < 0.01). However, the number of days-at-risk and number of coprescriptions of potentially interacting drugs among cisapride users increased on average by 13% and 9% per year, respectively. This increase was almost exclusively explained by a large increase in concomitant prescribing of clarithromycin, the most commonly used potentially interacting drug. Decreases in prevalence rates were observed for all individual potentially interacting drugs, except for concomitant use of fluconazole and miconazole.

CONCLUSIONS

Over the last few years, healthcare professionals have refrained from dispensing potentially interacting drugs to patients who use cisapride, probably as a result of drug warnings implemented during this period. The limited absolute effects result from an increase of coprescription and concomitant use of clarithromycin and fluconazole among cisapride users. Because therapeutically equivalent alternatives were available for both drugs, such combinations were avoidable. Communicating information on these drug-drug interactions to prescribers and pharmacists and inclusion of cardiovascular morbidity as a relative contraindication for prescribing cisapride with these drugs may substantially decrease the risk of potentially adverse events to cisapride.

Retrospective analysis of the effects of cisapride on the QT interval and QT dispersion in chronic hemodialysis patients

Cisapride is contraindicated in patients with end-stage renal disease (ESRD) and gastrointestinal motility disorders. Ventricular arrhythmias have been associated with both cisapride and hemodialysis (HD). However, reports conflict regarding the safety of cisapride in HD patients. We undertook this study to characterize the effects of cisapride on QT intervals and QT dispersion (QTD) in HD patients. Baseline and steady-state electrocardiograms (ECGs) were retrospectively selected for calendar year 1999 for each patient administered cisapride if ECGs showed sinus rhythm, potassium level was 3.5 mEq/dL or greater, and there was no pharmacokinetic drug interaction. QT intervals were measured by two investigators, and QTDs were calculated (maximum [QT(max)] - minimum QT interval [QT(min)]). Averages between investigator measures (+/- SD), presented for each value, were evaluated using Wilcoxon's signed-rank test. Thirty-one HD patients were administered cisapride. Seventeen patients failed to meet entry criteria, and no patient had a pharmacokinetic drug interaction. In included patients (6 men, 8 women), heart rates were 86.71 +/- 20.87 beats/min at baseline and 86.57 +/- 14.23 beats/min during treatment (P = not significant). Serum potassium levels were 4.97 +/- 1.2 mEq/dL at baseline and 4.94 +/- 0.76 mEq/dL during treatment (P = not significant). Average baseline QT(max) and QT(min) were 391.07 +/- 42.43 and 330.71 +/- 40.94 milliseconds, respectively. Treatment QT(max) and QT(min) were 391.43 +/- 38.2 and 343.93 +/- 35.69 milliseconds, respectively (P = not significant for both). QTD was 60.36 +/- 17.59 milliseconds at baseline and 47.5 +/- 19.59 milliseconds during treatment (P = 0.074). Mean corrected QT (QTc) intervals increased from 426.57 +/- 26.62 to 431.71 +/- 29.98 milliseconds (P = 0.55) from baseline to treatment. No ventricular arrhythmia was observed during at least 160 days (range, 2 to 830 days) of cisapride exposure. Two patients died during this study, both of other causes 4 days after discontinuing cisapride therapy. Cisapride did not significantly increase mean QTc interval, QT(max), or QTD in patients with ESRD managed by HD when potassium levels were stable and pharmacokinetic drug interactions were avoided.

Postmarketing reports of QT prolongation and ventricular arrhythmia in association with cisapride and Food and Drug Administration regulatory actions

OBJECTIVE

To describe the postmarketing safety data used in the risk assessment of cisapride and to summarize the regulatory actions of the Food and Drug Administration (FDA).

METHODS

The FDA analyzed reports of patients who developed QT prolongation, torsades de pointes, and ventricular arrhythmia in association with the use of cisapride to assess probable etiology and risk factors.

RESULTS

While cisapride was being marketed from 1993-1999, the FDA received reports of the following patients: 117 who developed QT prolongation; 107, torsades de pointes; 16, polymorphic ventricular tachycardia; 18, ventricular fibrillation; 27, ventricular tachycardia; 25, cardiac arrest; 16, serious (unspecified) arrhythmia; and 15, sudden death; for a total of 341 individual patients affected, following use of cisapride. Eighty (23%) of the 341 patients died. Deaths were directly or indirectly associated with an arrhythmic event. Factors that suggested an association with cisapride included a temporal relationship between use of cisapride and arrhythmia, the absence of identified risk factors and other explanations for arrhythmia in some patients, and cases of positive dechallenge and rechallenge. In most individuals, the arrhythmia occurred in the presence of risk factors (other drugs and/or medical conditions).

CONCLUSIONS

Postmarketing reports and pharmacokinetic and electrophysiological data provided evidence that cisapride is associated with the occurrence of QT prolongation and torsades de pointes. The risk of fatal arrhythmia with cisapride was believed to outweigh the benefit for the approved indication, treatment of nocturnal heartburn due to gastroesophageal reflux disease, leading to the drug's discontinuation in the United States.

Importance of QT interval determination and renal function assessment during antiarrhythmic drug therapy

A major concern associated with the use of antiarrhythmic drugs (AAD) is the occurrence of ventricular proarrhythmia, especially torsade de pointes (TdP). The AADs associated with TdP most commonly include quinidine, procainamide, disopyramide, sotalol, and the newer class III agents, such as ibutilide and dofetilide. It is not simply the administration and nature of an AAD but also several additional factors such as heart rate, ventricular hypertrophy, congestive heart failure, gender, age, concomitant drugs, and impaired drug clearance that influence TdP development. Dosing of these agents should be adjusted to take such factors into account to minimize the incidence of proarrhythmia.

Retrospective analysis of cisapride-induced QT changes in end-stage renal disease patients

BACKGROUND

This study involves a retrospective in-patient chart review of end-stage renal disease (ESRD) patients receiving haemodialysis to observe if cisapride significantly increases heart rate (HR), QT, and corrected QT (QTc) intervals on 12-lead electrocardiograms (ECGs).

METHODS

Medical records for 23 patients who were being treated with chronic maintenance haemodialysis and had >/=2 ECGs while on cisapride and >/=2 ECGs while off cisapride were obtained and reviewed. HR, QT, and QTc on all 12-lead ECGs, reason for admission, and past medical history were analysed.

RESULTS

A total of 529 ECGs (279 on/250 off cisapride) for 23 patients were included. The results, as calculated by each patient's individual averages (n=23), on vs off cisapride respectively, were HR, 88+/-14 vs 84+/-17 beats/min (P:=0.18); QT, 373+/-39 vs 382+/-45 ms (P:=0.24); and QTc, 443+/-27 vs 441+/-21 ms (P:=0.39). No significant difference was found in the number of admissions per month while on or off cisapride. No patient had an average QTc on or off cisapride that was >500 ms. One patient died from ventricular arrhythmia 12 days after discontinuing cisapride. The patient's QTc was significantly longer on vs off cisapride (487 vs 462 ms, P:=0. 007); however, this patient had an extensive cardiac history and multiple syncopal episodes prior to the use of cisapride.

CONCLUSIONS

This study found no significant overall difference in HR, QT, and QTc interval or admissions/month on vs off cisapride in ESRD patients receiving haemodialysis.

Drug interactions with cisapride: clinical implications

Cisapride, a prokinetic agent, has been used for the treatment of a number of gastrointestinal disorders, particularly gastro-oesophageal reflux disease in adults and children. Since 1993, 341 cases of ventricular arrhythmias, including 80 deaths, have been reported to the US Food and Drug Administration. Marketing of the drug has now been discontinued in the US; however, it is still available under a limited-access protocol. Knowledge of the risk factors for cisapride-associated arrhythmias will be essential for its continued use in those patients who meet the eligibility criteria. This review summarises the published literature on the pharmacokinetic and pharmacodynamic interactions of cisapride with concomitantly administered drugs, providing clinicians with practical recommendations for avoiding these potentially fatal events. Pharmacokinetic interactions with cisapride involve inhibition of cytochrome P450 (CYP) 3A4, the primary mode of elimination of cisapride, thereby increasing plasma concentrations of the drug. The macrolide antibacterials clarithromycin, erythromycin and troleandomycin are inhibitors of CYP3A4 and should not be used in conjunction with cisapride. Azithromycin is an alternative. Similarly, azole antifungal agents such as fluconazole, itraconazole and ketoconazole are CYP3A4 inhibitors and their concomitant use with cisapride should be avoided. Of the antidepressants nefazodone and fluvoxamine should be avoided with cisapride. Data with fluoxetine is controversial, we favour the avoidance of its use. Citalopram, paroxetine and sertraline are alternatives. The HIV protease inhibitors amprenavir, indinavir, nelfinavir, ritonavir and saquinavir inhibit CYP3A4. Clinical experience with cisapride is lacking but avoidance with all protease inhibitors is recommended, although saquinavir is thought to have clinically insignificant effects on CYP3A4. Delavirdine is also a CYP3A4 inhibitor and should be avoided with cisapride. We also recommend avoiding coadministration of cisapride with amiodarone, cimetidine (alternatives are famotidine, nizatidine, ranitidine or one of the proton pump inhibitors), diltiazem and verapamil (the dihydropyridine calcium antagonists are alternatives), grapefruit juice, isoniazid, metronidazole, quinine, quinupristin/dalfopristin and zileuton (montelukast is an alternative). Pharmacodynamic interactions with cisapride involve drugs that have the potential to have additive effects on the QT interval. We do not recommend use of cisapride with class Ia and III antiarrhythmic drugs or with adenosine, bepridil, cyclobenzaprine, droperidol, haloperidol, nifedipine (immediate release), phenothiazine antipsychotics, tricyclic and tetracyclic antidepressants or vasopressin. Vigilance is advised if anthracyclines, cotrimoxazole (trimethoprim-sulfamethoxazole), enflurane, halothane, isoflurane, pentamidine or probucol are used with cisapride. In addition, uncorrected electrolyte disturbances induced by diuretics may increase the risk of torsade de pointes. Patients receiving cisapride should be promptly treated for electrolyte disturbances.

Evidence for a cardiac ion channel mutation underlying drug-induced QT prolongation and life-threatening arrhythmias

The aim of this study was to test the hypothesis that some cases of drug-induced arrhythmias depend on genetic predisposition. Excessive prolongation of the QT interval and life-threatening arrhythmias (torsades de pointes or ventricular fibrillation) may occur in response to a variety of cardiac and noncardiac drugs, with detrimental effects on patient safety and the investments made by the pharmaceutical industry. Moss and Schwartz hypothesized that some drug-induced arrhythmias might represent cases of "forme fruste" of the congenital long QT syndrome (LQTS). The availability of molecular screening techniques for LQTS genes allowed us to test this hypothesis. An elderly female patient with documented cardiac arrest related to cisapride, a prokynetic drug that blocks I(Kr), and transiently prolonged QT interval underwent mutational analysis of the known LQTS-related genes performed by single-strand conformational polymorphism and DNA sequencing. Double-electrode voltage clamp in Xenopus oocytes as the expression system was used to study the in vitro cellular phenotype caused by the genetic defect in coexpression with the wild-type (WT) gene. Molecular analysis revealed a heterozygous mutation leading to substitution of a highly conserved amino acid in the pore region of KvLQT1. This mutation was present not only in the patient with ventricular fibrillation but also in her two adult asymptomatic sons who have a normal QT interval. In vitro expression of the mutated KvLQT1 protein showed a severe loss of current with a dominant negative effect on the WT-KvLQT1 channel. Our findings demonstrate that some cases of drug-induced QT prolongation may depend on a genetic substrate. Molecular screening may allow identification among family members of gene carriers potentially at risk if treated with I(Kr) blockers. Evolving technology may lead to rapid screening for mutations of candidate genes that cause drug-induced life-threatening arrhythmias and allow early identification of individuals at risk.

Prophylactic fluconazole promotes reepithelialization in full-face carbon dioxide laser skin resurfacing

BACKGROUND AND OBJECTIVE

Laser skin resurfacing is used to treat photodamaged skin, rhytids, and acne scarring. Many patients are placed on antibiotics and antivirals pre- and postoperatively. The purpose of this study was to determine whether prophylactic fluconazole increased the rate of reepithelialization in patients undergoing full-face CO(2) laser skin resurfacing.

STUDY DESIGN/MATERIALS AND METHODS

Ninety-one patients underwent full-face CO(2) laser skin resurfacing with the Coherent Ultrapulse 5000C. At least two passes of 300 mJ, density 5, were used except periocularly. Study group I consisted of 48 consecutive patients who received either cephalexin or ciprofloxacin for 7 days postoperatively. Study group II consisted of 43 patients who received 300 mg of fluconazole on postoperative days 3-8, in addition to ciprofloxacin. Both groups received acyclovir 400 mg t.i.d. pre- and postoperatively.

RESULTS

Time to complete reepithelialization was compared between the groups by t-test. Group II reepithelialized significantly faster than group I (7.65 +/- 1.20 days vs. 10.27 +/- 2.94 days; P < 0.0001). Ninety-five percent of patients receiving fluconazole (group II) healed completely by day 9 versus only 53% of patients in group I.

CONCLUSION

Fluconazole administered postoperatively between days 3 and 8 significantly promotes reepithelialization in patients undergoing full-face CO(2) laser skin resurfacing.

Review article: cardiac adverse effects of gastrointestinal prokinetics

Gastrointestinal prokinetics, such as metoclopramide, cisapride and levosulpiride, are widely used for the management of functional gut disorders. Recently, several studies have shown that cisapride (a partial 5-HT4 receptor agonist) can induce dose-dependent cardiac adverse effects, including lengthening of the electrocardiographic QT interval, syncopal episodes and ventricular dysrhythmias. Until recently, it was not clear whether these effects were dependent on 5-HT4 receptor activation or related to peculiar characteristics in the molecular structure of single agents within the benzamide class. Experimental evidence now favours the second hypothesis: cisapride possesses Class III antiarrhythmic properties and prolongs the action potential duration through blockade of distinct voltage-dependent K+ channels, thus delaying cardiac repolarization and prolonging the QT interval. Patients at risk of cardiac adverse effects are children, subjects with idiopathic, congenital or acquired long QT syndrome and, in particular, those receiving concomitant medication with Class III antiarrhythmic agents, some H1-receptor antagonists (e.g. terfenadine), or drugs such as azole antifungals (e.g. ketoconazole, itraconazole, miconazole and fluconazole) and macrolide antibacterials (e.g. erythromycin, clarithrod-mycin and troleandomycin), which can inhibit cisapride metabolism by interfering with the CYP3A4 isoenzyme.

The role of cisapride in the treatment of pediatric gastroesophageal reflux. The European Society of Paediatric Gastroenterology, Hepatology and Nutrition

BACKGROUND

Cisapride is a gastrointestinal prokinetic agent that is used worldwide in the treatment of gastrointestinal motility-related disorders in premature infants, full-term infants, and children. Efficacy data suggest that it is the most effective commercially available prokinetic drug.

METHODS

Because of recent concerns about safety, a critical and in-depth analysis of all reported adverse events was performed and resulted in the conclusions and recommendations that follow.

RESULTS

Cisapride should only be administered to patients in whom the use of prokinetics is justified according to current medical knowledge. If cisapride is given to pediatric patients who can be considered healthy except for their gastrointestinal motility disorder, and the maximum dose does not exceed 0.8 mg/kg per day in 3 to 4 administrations of 0.2 mg/kg (not exceeding 40 mg/d), no special safety procedures regarding potential cardiac adverse events are recommended. However, if cisapride is prescribed for patients who are known to be or are suspected of being at increased risk for drug-associated increases in QTc interval, certain precautions are advisable. Such patients include those:(1) with a previous history of cardiac dysrhythmias, (2) receiving drugs known to inhibit the metabolism of cisapride and/or adversely affect ventricular repolarisation, (3) with immaturity and/or disease causing reduced cytochrome P450 3A4 activity, or (4) with electrolyte disturbances. In such patients, ECG monitoring to quantitate the QTc interval should be used before initiation of therapy and after 3 days of treatment to ascertain whether a cisapride-induced cardiac adverse effect is present.

CONCLUSIONS

With rare exceptions, the total daily dose of cisapride should not exceed 0.8 mg/kg divided into 3 or 4 approximately equally spaced doses. If higher doses than this are given, the precautions above are advisable. In any patient in whom a prolonged QTc interval is found, the dose of cisapride should be reduced or the drug discontinued until the ECG normalizes. If the QTc interval returns to normal after withdrawal of cisapride, and the administration of cisapride is considered to be justified because of its efficacy and absence of alternative treatment options, cisapride can be restarted at half dose with control of the QTc interval. Unfortunately, at present, normal ranges of QTc interval in children are unknown. However, a critical analysis of the literature suggests that a duration of less than 450 milliseconds can be considered to be within the normal range and greater than 470 milliseconds as outside it.