QTc-interval abnormalities and psychotropic drug therapy in psychiatric patients

QTc interval, CYP2D6 and CYP2C9 genotypes and risperidone plasma concentrations

The role of certain drug metabolizing enzymes in cardiotoxicity, such as CYP2D6 for thioridazine, has been suggested. Risperidone has been shown to inhibit the delayed rectifier leading to lengthening of cardiac repolarization. The heart-rate corrected QT (QTc) interval lengthening has been reported in psychiatric patients receiving risperidone under steady-state conditions. CYP2D6 is involved in the metabolism of risperidone to 9-hydroxy (OH)-risperidone. CYP2C9 enzyme is also involved in the metabolism of several psychotropic drugs, although there are no data about its implication in risperidone metabolism. The present study aimed to evaluate the influence of CYP2D6 and CYP2C9 genotypes, and plasma concentrations of risperidone and 9-OH-risperidone on the QTc interval in patients under steady-state conditions. The relevance of CYP2D6 and CYP2C9 genotypes on risperidone metabolism was also analysed. Thirty-five White European psychiatric patients receiving risperidone monotherapy were studied. QTc interval was longer (p < 0.05) in subjects with one active CYP2D6 gene compared to those with two. The number of CYP2D6 active genes was related to the dose-corrected plasma concentration of risperidone (p < 0.05), the active moiety (risperidone plus 9-OH-risperidone) (p < 0.05) and the risperidone/9-OH-risperidone ratio (p < 0.05). CYP2C9 genotypes were not related to plasma concentrations of risperidone or 9-OH-risperidone, nor QTc interval. The results suggest that CYP2D6, but not CYP2C9, may be related to QTc lengthening during treatment with risperidone. The effect of the CYP2D6 genotype in risperidone metabolism is also shown.

Potential for drug interactions involving cytochromes P450 2D6 and 3A4 on general adult psychiatric and functional elderly psychiatric wards

AIMS

To assess the potential for interactions involving cytochromes P450 2D6 (CYP2D6) and 3A4 (CYP3A4) between drugs prescribed in a city in-patient psychiatric service.

METHODS

Prescription information was obtained from all 236 patients in general adult wards and all 87 patients in functional elderly wards under a city psychiatric service. The frequencies with which combinations of drugs expected to interact via CYP2D6 or CYP3A4 were documented and compared between these two settings.

RESULTS

All 2089 drug prescriptions, of which 1237 (59%) were administered, were analyzed. One hundred and seventy-two patients (73%) on adult wards and 59 (68%) on functional elderly wards were prescribed at least one drug metabolized by and/or inhibiting CYP2D6, the difference being nonsignificant (95% confidence interval on the difference -6.3%, 16.4%). Anticipated interactions from 62/82 CYP2D6-related combinations prescribed on adult wards (27/100 patients) and 19/30 prescribed to elderly patients (22/100 patients) were judged to be clinically important or potentially clinically important. The proportion of patients on functional elderly wards prescribed at least one drug interacting with CYP3A4 (87%) was significantly greater than that for patients on adult wards (57%, P < 0.001). The frequency of interactions involving CYP3A4 was significantly greater on functional elderly than adult wards (43/100 vs 22/100 patients, P < 0.025, 95% confidence interval on the difference 4, 38/100).

CONCLUSIONS

Our findings confirm extensive polypharmacy on general adult psychiatric and functional elderly psychiatric wards. A substantial proportion of patients were receiving combinations of drugs that interact with CYP2D6 and/or CYP3A4, many of which are known to produce clinically important interactions. Doctors practising in old age psychiatry should be aware that patients on functional elderly wards are at increased risk of clinically important CYP3A4 interactions. Psychiatrists should consider the pharmacokinetic implications of drugs prescribed for use 'as needed', because of the potential for unpredictable interactions.

Haloperidol in palliative care

Haloperidol is one of 20 'essential' medications in palliative care. Its use is widespread in palliative care patients. The pharmacology of haloperidol is complex and the extent and severity of some of its adverse effects, particularly extrapyramidal adverse effects (EPS), may be related to the route of administration. Indications for the use of haloperidol in palliative care are nausea and vomiting and delirium. Adverse effects include EPS and QT prolongation. Sedation is not a common adverse effect of haloperidol. It is important that palliative care practitioners have a comprehensive understanding of the indications, doses, adverse effects and pharmacology of haloperidol. This review is intended to address these issues.

Gender difference in QTc prolongation of people with mental disorders

BACKGROUND: We examined gender difference in QTc interval distribution and its related factors in people with mental disorders. METHODS: We retrospectively reviewed medical charts of patients discharged from a university psychiatric unit between November 1997 and December 2000. Subjects were 328 patients (145 males and 183 females) taking psychotropics at their admission. We examined patient characteristics, medical history, diagnosis, and medication before admission. RESULTS: Mean QTc interval was 0.408 (SD = 0.036). QTc intervals in females were significantly longer than those in males. QTc of females without comorbidity was significantly longer than that of males. CONCLUSION: The influence of gender difference on QTc prolongation in people with mental disorders merits further research.

Hidden cardiac lesions and psychotropic drugs as a possible cause of sudden death in psychiatric patients: a report of 14 cases and review of the literature

OBJECTIVE

To confirm the hypothesis that psychotropic drugs, especially neuroleptics, lithium, and antidepressants, are implicated as a cause of unexpected sudden death in psychiatric patients because of their cardiotoxicity, especially when hidden cardiac lesions are present.

METHOD

We performed a full pathological examination of 14 psychiatric patients who unexpectedly and suddenly died between 1980 and 1999.

RESULTS

Neuroleptics were involved in 13 instances, antidepressants in 9, and anxiolytics in 5. Psychotropic drugs were combined in all but a single patient. In all 14 patients, toxicological analyses discarded drug overdose as cause of death. At postmortem examination, the brain and abdominal organs were normal. In 13 patients, the following lesions were found in the heart and lungs: dilated cardiomyopathy (6 patients), left ventricular hypertrophy (2 patients, 1 of which was associated with mitral prolapse and anomalies of His bundle), arrhythmogenic cardiopathy of the right ventricle (1 patient), pericarditis (1 patient), mitral prolapse (1 patient), muscular bridge on the anterior interventricular artery (1 patient), and Mendelsons syndrome (1 patient). In 1 case, no changes were seen. Most of the drugs that were taken immediately prior to death can induce arrhythmias either by prolonging the QT interval, potentially resulting in torsades de pointes, or by widening QRS complexes, possibly leading to reentry and ventricular fibrillation.

CONCLUSION

Our findings suggest that the arrhythmogenic effects of psychotropic drugs can be exacer bated when preexisting hidden cardiac lesions are present and can result in sudden death. Patients should be systematically evaluated for cardiac lesions prior to starting any treatment with psychotropic drugs; the minimal effective dosage should be used.

Pharmacokinetic Factors in the Adverse Cardiovascular Effects of Antipsychotic Drugs

Antipsychotics may cause serious adverse cardiovascular effects, including prolonged QT interval and sudden death. This review considers antipsychotic-induced cardiovascular events from three perspectives: high-risk drugs, high-risk individuals and high-risk drug interactions. Pharmacokinetic drug interactions involving the cytochrome P450 (CYP) enzymatic pathway and pharmacodynamic interactions leading to direct cardiotoxic effects are discussed. Original reports on antipsychotic-induced drug interactions are reviewed, with consideration of management guidelines. The literature was reviewed from 1 January 1966 to 1 February 2002. The literature search revealed only 12 original articles published on antipsychotic drug interactions leading to cardiovascular adverse events. Only 4 of the 12 reports were prospective studies; the remainder were either retrospective or anecdotal.Although poor study designs preclude a definitive statement, it appears that pharmacokinetic interactions primarily involved the CYP2D6 and CYP3A4 enzymatic pathways. Those involving the CYP2D6 isozyme included interactions with tricyclic antidepressants, selective serotonergic reuptake inhibitors and beta-blockers. Among these drug interactions, tricyclic antidepressants were most likely to reach clinical significance because of their limited therapeutic index. Drug interactions related to the CYP3A4 pathway were generally less severe, and involved high-potency antipsychotics coadministered with inhibitors such as clarithromycin. Strategies are discussed for the management of adverse cardiovascular events related to antipsychotic drug interactions, including the use of an algorithm. Large, randomised, placebo-controlled studies with strict inclusion criteria are needed to determine the role that antipsychotics play in QT prolongation and sudden death.

Serious cardiovascular events and mortality among patients with schizophrenia

This study compared the risks of cardiovascular morbidity and mortality in people with schizophrenia who use antipsychotic medications to risks in individuals without schizophrenia in a large managed care organization. A sample of 1920 schizophrenia patients was matched by age, sex, date, and health plan to 9600 persons randomly selected from the health plan general membership. Death, myocardial infarction, arrhythmia, and new-onset diabetes were identified using a National Death Index search and medical claims records. The adjusted all-cause mortality rate in the group of treated schizophrenics was four times higher than in the control group regardless of whether patients were given a typical or an atypical antipsychotic medication. Users of typical antipsychotics had a fivefold higher risk of myocardial infarction than the control subjects. Among patients with schizophrenia, cardiovascular risk was inversely associated with intensity of use of antipsychotic drugs, suggesting that the observed risks may not be due to a simple or direct effect of drugs. Patients treated for schizophrenia had higher rates of new-onset diabetes than did the general population controls. This risk was most pronounced in persons with more intense exposure to drugs and appeared to be indistinguishable in users of typical antipsychotics, of atypical products, or of both.

Prolonged QTc intervals in medicated patients with schizophrenia

Psychotropic drugs have been associated with sudden deaths and the lengthening of corrected-QT interval (QTc) on the electrocardiogram which may be a precursor of life-threatening arrhythmias as reported with some of these drugs. The objectives of this study were to measure the frequency of QTc lengthening in patients with schizophrenia receiving psychotropic drugs, and to assess whether QTc lengthening was associated with certain psychotropic drugs and other risk factors. One hundred and sixty three patients with schizophrenia (104 males and 59 females) were included in the study. Clinical and demographic data were collected from the case records. One hundred healthy volunteers were recruited to establish values for upper limits of normal for measurement of QTc interval and dispersion. Eleven (6.7%) of the patients had a prolonged QTc interval. The significant predictors obtained from a logistic regression modelling were chlorpromazine, flupenthixol decanoate and fluphenazine decanoate. Caution should be exercised and monitoring with ECG should be considered in patients prescribed chlorpromazine and depot antipsychotic medications even at recommended doses.

Anaesthesia: the patient's point of view

Patients scheduled for surgical procedures continue to express concerns about their safety, outcome, and comfort. All medical interventions carry risks, but the patient often considers anaesthesia as the intervention with the greatest risk. Many still worry that they will not wake up after their surgery, or that they will be awake during the operation. Such events have received attention from the media, but are very rare. Challenges to improve the comfort of patients continue, especially with regard to the almost universal problems of nausea, vomiting, and pain after surgery. A newer concern is that patients will develop some degree of mental impairment that may delay return to a full work and social lifestyle for days and weeks. Developments in technology, education, and training have had a major effect on anaesthetic practice, so that anaesthesia is increasingly regarded as safe for the patient. This article explores patients' concerns, and considers whether science and technology help to provide solutions to these complex difficulties.

QT Prolongation and Fatal Arrhythmias: A Review of Clinical Implications and Effects of Drugs

A long QT interval due to prolonged repolarization may be associated with a polymorphic ventricular tachycardia known as torsades de pointes. During marked prolongation of the action potential (long QT) early after depolarizations may occur, which when propagated may trigger an arrhythmia. The duration of QTc interval is the major determinant of the risk of drug-induced torsades. Congenital long QT syndrome, female gender, hypokalemia and use of sympathomimetics increase the risk of torsades, and potentiate the QT prolonging effects of drugs. Antiarrhythmics that block the potassium channel prolong the QT and increase the risk for torsades (amiodarone, sotalol, quinidine, procainamide, ibutilide, disopyramide). Additionally, some macrolide and fluoroquinolone antibiotics, antipsychotic and antidepressant drugs, serotonin agonists of the triptan class, cisapride, dolasetron and others have been reported to be associated with QT prolongation or cases of torsades. Drug-induced effects on the QT interval with the associated possibility of inducing fatal arrhythmias have become a new challenge for the practitioner, the drug development process and the regulatory agencies.

New Generation Antipsychotic Drugs and QTc Interval Prolongation

BACKGROUND: Recent regulatory and clinical concerns have brought into sharp focus antipsychotic drug-induced QTc interval prolongation, torsades de pointes, and sudden cardiac death. Several new generation (atypical) antipsychotic drugs have either been withdrawn from clinical use or delayed in reaching the marketplace due to these concerns. Because torsades de pointes is rarely found, QTc interval prolongation serves as a surrogate marker for this potentially life-threatening arrhythmia. Current methods of calculating this electrocardiographic parameter have limitations. The primary care physician is a key member of the team managing a patient who requires administration of antipsychotic drugs. This article focuses on new generation antipsychotic drugs and principles useful to both the primary care physician and the psychiatrist. METHOD: PubMed was searched in September 2002 using the terms antipsychotic drug and QT interval. References were examined from review articles describing antipsychotic drugs and the QT interval. The author's files gathered over the past 20 years on the QT interval were also reviewed. RESULTS: Nine cases were available in which drug-induced QTc interval prolongation was associated with new generation antipsychotic drug administration. Eight cases were taken from the literature, and the author added one additional report. The newer agents involved were risperidone, quetiapine, and ziprasidone. In at least 8 cases, there was evidence of other risk factors associated with QTc interval prolongation. In one case frequently referenced in the literature, the authors misunderstood their own data showing that QTc interval prolongation did not relate to delayed ventricular repolarization. In another instance, 2 authors reported on the same patient, with important information missing from both articles. No evidence of torsades de pointes appeared in any of the 9 cases. CONCLUSIONS: No evidence is currently available in the literature implicating new generation antipsychotic drugs in the production of torsades de pointes. However, the absence of such evidence does not prove that newer antipsychotic drugs do not cause torsades de pointes. Among patients free of risk factors for QTc interval prolongation and torsades de pointes, current literature does not dictate any specific consultative or laboratory intervention before administering new generation antipsychotic drugs. When risk factors are present, evaluation and intervention specific to those risk factors should dictate the clinician's course of action. More specific guidelines for monitoring the QT interval and risk of torsades de pointes await improved methods of measuring the QTc interval relevant to each patient.

Prolongation of the QT interval in palliative care patients

Prolonged QT interval on the electrocardiogram (ECG) is associated with an increased risk of cardiac arrhythmia and sudden death. Many drugs used in palliative medicine increase the QT interval and several have had their licenses withdrawn or severely restricted. The relative importance of prolonged QT interval will increase for palliative medicine physicians when dealing with patients with longer prognoses and especially cardiac disease. Given these safety concerns, the aim of this study was to determine the prevalence of a prolonged QT interval in palliative care patients who were not in the terminal stage and were referred to a specialist service. Of 300 patients, 47 (16%) had prolonged QTc but only two had QT >500ms. The presence of coexistent cardiac disease or high levels of serum alkaline phosphatase appear to be the clinical features most robustly associated with a prolonged QTc. Although prolonged QTc is relatively common in patients referred to a specialist palliative care service, severely prolonged QT is rare.

The antiemetic efficacy of droperidol added to morphine patient-controlled analgesia: a randomized, controlled, multicenter dose-finding study

The antiemetic dose response of droperidol when it is added to patient-controlled analgesia with morphine is not well known. We randomly allocated adults who received postoperative morphine patient-controlled analgesia (1-mg bolus, 5-min lockout) to one of four regimens: no droperidol (control) or 5, 15, or 50 micro g of droperidol per milligram of morphine. Efficacy and adverse effects were recorded during 24 h and were analyzed with number needed to treat (NNT) and number needed to harm with 95% confidence intervals. Data from 82 controls, 82 patients receiving droperidol 5 micro g, 82 receiving droperidol 15 micro g, and 83 receiving droperidol 50 micro g were analyzed. Average consumption of droperidol per 24 h was 0.2 mg with the 5- micro g regimen, 0.61 mg with the 15- micro g regimen, and 2.04 mg with the 50- micro g regimen. In controls, the incidence of nausea was 48.8%; with droperidol 5 micro g, it was 42.7% (NNT compared with control, 16 [95% confidence interval, 4.7 to -11]); with 15 micro g, it was 32.9% (NNT, 6.3 [3.3-100]); and with 50 micro g, it was 21.7% (NNT, 3.7 [2.4 to 7.6]). In controls, the incidence of vomiting was 24.4%; with droperidol 5 micro g, it was 23.2% (NNT compared with control, 82 [7 to -8.5]); with 15 micro g, it was 22.0% (NNT, 41 [6.5 to -9.6]); and with 50 micro g, it was 12% (NNT, 8.1 [4.2-142]). In controls, the incidence of pruritus was 12.2%; with droperidol 5 micro g, it was 6.1% (NNT compared with control, 16 [6.7 to -37]); and with 15 and 50 micro g, it was 2.4% (NNT, 10 [5.7-52]). In controls, the incidence of sedation was 2.4%; with droperidol 5 micro g, it was 8.5% (number needed to harm (NNH) compared with control, 16 [7.7 to -123]); with 15 micro g, it was 6.1% (NNH, 27 [10 to -40]); and with 50 micro g, it was 18.1% (NNH, 6.4 [4.1-15]). There were no extrapyramidal symptoms and no cardiac adverse events. There was no difference in patient satisfaction. The optimal antiemetic dose of droperidol is 15-50 micro g/mg of morphine. Larger doses may have more antivomiting efficacy but are likely to be unacceptably sedating.

Antipsychotic induced prolongation of QTc interval treated with magnesium

We report the case of a patient on antipsychotic medication, who developed an abnormal QTc interval, which normalized following treatment with oral magnesium sulphate.

Acute cardiac failure in neuroleptic malignant syndrome

We present a case of rapid onset acute cardiac failure developing as part of neuroleptic malignant syndrome in a 35-year-old woman following treatment with thioridazine and lithium. Post mortem histology of cardiac and skeletal muscle showed similar changes of focal cellular necrosis and vacuolation suggesting a common disease process.

Effects of sex on the pharmacokinetic and pharmacodynamic properties of quinidine

AIMS

To investigate the source of the apparent increased susceptibility of women to develop QT interval prolongation and torsade de pointes after the administration of drugs that delay cardiac repolarization.

METHODS

Plasma quinidine concentrations and electrocardiographic changes (QRS and QT intervals) were measured over 24 h following the administration of single oral doses of the QT prolonging drug quinidine (3 mg kg(-1)) and compared between 27 male and 21 female healthy volunteers.

RESULTS

There were no significant differences between males and females in plasma quinidine concentrations or in calculated pharmacokinetic variables. Maximum quinidine concentrations in males and females were 997 +/- 56 and 871 +/- 57 ng ml(-1), respectively (mean difference (-125, 95% confidence intervals (CI) -239, 11 ng ml(-1), P = NS). Quinidine lengthened actual (QTa) and corrected (QTc) QT intervals and the QRS interval to a greater extent in females than males (P < 0.001 for each), but there were no significant sex differences detected in the effects of quinidine on the heart rate corrected JT interval. Maximum prolongation of QTc interval was observed 2 h after quinidine and was significantly greater in women (33 +/- 16 vs 24 +/- 17 ms, mean difference 9 +/- 20 ms, 95% CI 3, 15, P = 0.037). At this time mean differences (95% CI) were 1.0 min(-1) (-2.5, 4.4, P = NS) for heart rate, 5.5 ms (3.5, 7.6, P = 0.05) for the QRS and 3.4 ms (-2.5, 9.3, P = NS) for the JTc intervals.

CONCLUSIONS

Quinidine-induced increases in QTc were larger in females, but no sex differences in quinidine pharmacokinetics were found. The disparity in prolongation of cardiac repolarization is thus due to a pharmacodynamic difference which appears more complex than simply an increase in repolarization delay in females.

Effects of intramuscular olanzapine vs. haloperidol and placebo on QTc intervals in acutely agitated patients

Prolongation of the QTc interval has been reported during treatment with oral antipsychotic agents and may be more pronounced during parenteral administration. Pooled QTc interval data from acutely agitated patients across four double-blind trials were compared. Databases included: placebo-controlled [two schizophrenia, one bipolar mania trials (n=565)]; haloperidol-controlled [two schizophrenia trials (n=482)]; geriatric placebo-controlled [1 dementia trial (n=204)]. Patients received 1-3 injections of intramuscular (IM) olanzapine (2.5-10 mg/injection), IM haloperidol (7.5 mg/injection), or IM placebo. At 2 and 24 h after IM olanzapine treatment, the mean QTc interval decreased approximately 3 ms from baseline in the placebo- and haloperidol-controlled databases. When there was a statistically significant difference between IM olanzapine and IM placebo, QTc intervals decreased during treatment with IM olanzapine and increased with IM placebo. The incidences of prolonged (endpoint >/=99th percentile of healthy adults or >/=500 ms) or lengthened (increase >/=60 ms) QTc intervals during treatment with IM olanzapine (<3% placebo- and haloperidol-controlled databases, <12% geriatric placebo-controlled database) were never significantly greater than with comparators. These data suggest that IM olanzapine has a favorable QTc interval profile in acutely agitated patients with schizophrenia, bipolar mania, or dementia.

Ziprasidone in the management of schizophrenia : the QT interval issue in context

Ziprasidone is a new atypical antipsychotic recently marketed in a number of countries. Its main advantage over other atypical and typical drugs is its low propensity for causing weight gain. However, ziprasidone has been shown to prolong to some extent the cardiac corrected QT (QTc) interval, a property shared by a number of other antipsychotics. Prolongation of the QTc interval is linked to the ventricular tachyarrhythmia torsade de pointes, which is occasionally fatal, although the precise association between QTc changes and risk of sudden cardiac death has not been determined. QTc prolongation is certainly linked in some way to an increased risk of sudden cardiac death, and this may explain the recent, somewhat preliminary, reports of increased risk associated with use of some antipsychotics. Ziprasidone prolongs QTc to a moderate degree, though to a greater extent than quetiapine, risperidone, olanzapine and haloperidol. There is also preliminary evidence that ziprasidone blocks the delayed potassium rectifier channel in cardiac cells. Because of this, and despite the fact that no increased risk of arrhythmia or sudden death has been demonstrated for ziprasidone, some caution is required. Ziprasidone should be avoided in patients with some types of cardiac disease and with uncontrolled electrolyte disturbance. Coprescription of ziprasidone with other drugs that prolong the QT interval should be avoided where possible. When cross-tapering with other antipsychotics, care should be taken to avoid high total load of antipsychotics, and cross-tapering with drugs known to prolong QT interval at normal clinical doses should be avoided. Under most clinical circumstances, however, ziprasidone may be safely used without ECG monitoring or other special precautions. Its effect on QT interval and possible effect on risk of arrhythmia should be balanced with the observation that the drug has a more favourable effect on bodyweight and glucose homeostasis (and so perhaps cardiac risk) than many other antipsychotics.

Clinical relevance and management of drug-related QT interval prolongation

Much attention recently has focused on drugs that prolong the QT interval, potentially leading to fatal cardiac dysrhythmias (e.g., torsade de pointes). We provide a detailed review of the published evidence that supports or does not support an association between drugs and their risk of QT prolongation. The mechanism of drug-induced QT prolongation is reviewed briefly, followed by an extensive evaluation of drugs associated with QT prolongation, torsade de pointes, or both. Drugs associated with QT prolongation are identified as having definite, probable, or proposed associations. The role of the clinician in the prevention and management of QT prolongation, drug-drug interactions that may occur with agents known to affect the QT interval, and the impact of this adverse effect on the regulatory process are addressed.

Factors influencing prescription of CNS medications in different elderly populations

Factors influencing the use of neuroleptic and other CNS-acting medications ('antidepressants' and 'hypnotics/anxiolytics') were examined in different elderly populations (> 65 years): long-stay care hospital subjects (n = 381), nursing home subjects (n = 1247), private residential home subjects (n = 321), statutory residential home subjects (n = 525), old age psychiatry facility subjects (n = 48), community dwellers (n = 97), in different geographical areas (urban n = 1223 and rural n = 1396). Neuroleptics were prescribed in 28% of the individuals, hypnotics/anxiolytics in 33% and antidepressants in 12%. Prescription of neuroleptics was significantly predicted by institutional placement (other than long-stay care hospital facility), lower cognitive function and rural geographical area. Age greater than 75 years and lower functional score (lower dependency) significantly decreased the likelihood of receipt of neuroleptics. Antidepressant use was significantly less likely in male subjects, patients with cognitive impairment and patients greater than 85 years. Institutional placement (other than long-stay care hospital facility and old age psychiatry facility) and rural locality predicted increased likelihood of antidepressant prescription. Institutional placement (other than long-stay care hospital facility) and geographical (rural) location were significant independent predictors of hypnotic/anxiolytic use. Prescription of hypnotic/anxiolytic drug class was significantly less likely in those individuals with lower cognitive status. In this representative elderly cohort, patient characteristics: age, sex, cognitive score, functional score, place of residence and geographical location markedly influenced drug utilisation.

The antipsychotic drug chlorpromazine inhibits HERG potassium channels

(1) Acquired long QT syndrome (aLQTS) is caused by prolongation of the cardiac action potential because of blockade of cardiac ion channels and delayed repolarization of the heart. Patients with aLQTS carry an increased risk for torsade de pointes arrhythmias and sudden cardiac death. Several antipsychotic drugs may cause aLQTS. Recently, cases of QTc prolongation and torsade de pointes associated with chlorpromazine treatment have been reported. Blockade of human ether-a-go-go-related gene (HERG) potassium channels, which plays a central role in arrhythmogenesis, has previously been reported to occur with chlorpromazine, but information on the mechanism of block is currently not available. We investigated the effects of chlorpromazine on cloned HERG potassium channels to determine the biophysical mechanism of block. (2) HERG channels were heterologously expressed in Xenopus laevis oocytes, and ion currents were measured using the two-microelectrode voltage-clamp technique. (3) Chlorpromazine blocked HERG potassium channels with an IC(50) value of 21.6 micro M and a Hill coefficient of 1.11. (4) Analysis of the voltage dependence of block revealed a reduction of inhibition at positive membrane potentials. (5) Inhibition of HERG channels by chlorpromazine displayed reverse frequency dependence, that is, the amount of block was lower at higher stimulation rates. No marked changes in electrophysiological parameters such as voltage dependence of activation or inactivation, or changes of the inactivation time constant were observed. (6) In conclusion, HERG channels were blocked in the closed and activated states, and unblocking occurred very slowly.

Adverse effects associated with physical restraint

OBJECTIVE

Restraint use is not monitored in the US, and only institutions that choose to do so collect statistics. In 1999, investigative journalists reported lethal consequences proximal to restraint use, making it a life-and-death matter that demands attention from professionals. This paper reviews the literature concerning actual and potential causes of deaths proximal to the use of physical restraint.

METHOD

Searching the electronic databases Medline, Cinahl, and PsycINFO, we reviewed the areas of forensics and pathology, nursing, cardiology, immunology, psychology, neurosciences, psychiatry, emergency medicine, and sports medicine.

CONCLUSIONS

Research is needed to provide clinicians with data on the risk factors and adverse effects associated with restraint use, as well as data on procedures that will lead to reduced use. Research is needed to determine what individual risk factors and combinations thereof contribute to injury and death.

Tolerability and efficacy of clozapine combined with lithium in schizophrenia and schizoaffective disorder

The safety and tolerability of clozapine combined with lithium were investigated because of potential additive risks as well as frequent usage in clinical practice. Ten hospitalized schizophrenic and 10 schizoaffective patients receiving clozapine maintenance therapy with partial therapeutic response were studied in a randomized controlled trial. CGI and PANSS outcome ratings were employed and a cognitive battery was administered at baseline and after 4 weeks of lithium and placebo administration. Barnes and UKU side effect ratings and laboratory safety data were obtained. Combined lithium-clozapine treatment was well tolerated except for reversible neurotoxic reactions in two schizophrenic patients. Safety measures showed no significant variations, even during lithium toxicity. Total WBC and absolute granulocyte counts increased with lithium and declined with placebo. Schizoaffective patients improved with lithium on CGI and PANSS total and negative symptom scales and the cognitive measures, whereas schizophrenic patients did not. Lithium added to clozapine in treatment regimens for hospitalized, treatment-resistant, schizoaffective patients appears to afford potential benefit without harmful effects; for schizophrenic patients, however, it did not afford improvement but posed a risk of lithium toxicity.

The relevance of prolonged QTc measurement to pediatric psychopharmacology

OBJECTIVE

To consider the relevance of prolonged QTc (QT interval corrected for rate) to pediatric psychopharmacology.

METHOD

The authors reviewed publications on QTc prolongation and publications on sudden death in Medline from 1968 to November 2002.

RESULTS

The search yielded more than 20,000 publications. Review manuscripts with clinical recommendations outnumber the few pediatric studies of QTc duration during treatment. Most reviews have been published in the past 5 years, during a time when the Food and Drug Administration restricted five psychotropic medications because of QTc prolongation (sertindole: not approved; thioridazine, mesoridazine, and droperidol: black-box warning; and ziprasidone: bolded warning) and nine somatic medications because of QTc prolongation.

CONCLUSION

Pretreatment screening, careful selection of psychotropic and/or somatic medication combinations, and recognition of QTc prolongation in electrocardiographic tracings during treatment with medications that prolong QTc are important components of clinical practice.

Effects of licence change on prescribing and poisons enquiries for antipsychotic agents in England and Scotland

AIMS

To examine the effect of licence change for thioridazine at the end of 2000 on the prescription of antipsychotic drugs in England and Scotland, and investigate changes in poisons information inquiries and, for Edinburgh, poisons admissions.

METHODS

Prescription data for antipsychotic drugs were obtained for England and Scotland and quarterly trends examined for 2000 and 2001. Accesses to the UK National Poisons Information Service website TOXBASE for antipsychotic products were examined for the same period. For Scotland telephone enquiry data, and admission data to the Edinburgh Poisons Unit were also evaluated. Trends in poisonings were compared with prescribing change.

RESULTS

In England prescriptions for thioridazine fell rapidly in 2001 from approximately 35% of market share to less than 5%, and were replaced by risperidone, chlorpromazine and olanzapine. TOXBASE accesses fell from 39.3% of antipsychotics to 4.4%. Accesses for chlorpromazine, olanzapine and risperidone increased. In Scotland prescribing of thioridazine was similar to changes in England, but it was principally replaced by chlorpromazine. These changes were mirrored by TOXBASE accesses, telephone enquiries and in-patient admissions. The ratio of TOXBASE accesses for thioridazine to prescription numbers for the drug increased after the licence change.

CONCLUSIONS

Licence change produced rapid change in prescribing behaviour within 3 months. Prescribing behaviour in England and Scotland was different. Changes in prescribing were mirrored by changes in accesses for poisons information in both England and Scotland, and in Edinburgh by hospital admissions. The increase in the ratio of TOXBASE accesses to prescriptions for thioridazine suggests doctors may have become more aware of its potential toxicity.

Investigation of the potential of clozapine to cause torsade de pointes

Antipsychotics are frequently associated with QTc interval prolongation, a proposed marker for vulnerability to fatal ventricular arrhythmias, e.g. torsade de pointes (TdP). Little has been published on this topic in relation to clozapine. The objectives of this review were to: (i) calculate the frequency of QTc interval prolongation, T-wave abnormalities, TdP, ventricular tachycardia/fibrillation and sudden unexplained death in patients treated with clozapine and thioridazine from clinical trial and post-marketing reports; (ii) to compare these data with published findings for haloperidol, risperidone, olanzapine, sertindole and ziprasidone; and (iii) to correlate these clinical data with results from preclinical tests presently considered to be of predictive value for a compound's potential to cause QTc interval prolongation and TdP. A review of the global Novartis databases for clozapine and thioridazine and a Medline/Internet search for information on these cardiac events and for preclinical effects on the human ether-a-go-go related gene channels, action potential duration, and QT interval changes produced by the selected antipsychotics were performed. The clozapine database (2.8 million patient-years spanning 27 years) demonstrated that at therapeutic doses all but three reports of QTc interval prolongation and both of TdP were confounded by relevant co-medication/comorbidity. The literature review revealed that all antipsychotics considered except clozapine induced TdP and/or QTc interval prolongation at therapeutic doses. Preclinical in vitro tests appear to overestimate the risk of clozapine, haloperidol and risperidone to prolong QTc interval in patients and underestimate such a risk for sertindole and ziprasidone. Extrapolation of in vitro results to clinical events requires qualified interpretation.

Interindividual variability of the clinical pharmacokinetics of methadone: implications for the treatment of opioid dependence

Methadone is widely used for the treatment of opioid dependence. Although in most countries the drug is administered as a racemic mixture of (R)- and (S)- methadone, (R)-methadone accounts for most, if not all, of the opioid effects. Methadone can be detected in the blood 15-45 minutes after oral administration, with peak plasma concentration at 2.5-4 hours. Methadone has a mean bioavailability of around 75% (range 36-100%). Methadone is highly bound to plasma proteins, in particular to alpha(1)-acid glycoprotein. Its mean free fraction is around 13%, with a 4-fold interindividual variation. Its volume of distribution is about 4 L/kg (range 2-13 L/kg). The elimination of methadone is mediated by biotransformation, followed by renal and faecal excretion. Total body clearance is about 0.095 L/min, with wide interindividual variation (range 0.02-2 L/min). Plasma concentrations of methadone decrease in a biexponential manner, with a mean value of around 22 hours (range 5-130 hours) for elimination half-life. For the active (R)-enantiomer, mean values of around 40 hours have been determined. Cytochrome P450 (CYP) 3A4 and to a lesser extent 2D6 are probably the main isoforms involved in methadone metabolism. Rifampicin (rifampin), phenobarbital, phenytoin, carbamazepine, nevirapine, and efavirenz decrease methadone blood concentrations, probably by induction of CYP3A4 activity, which can result in severe withdrawal symptoms. Inhibitors of CYP3A4, such as fluconazole, and of CYP2D6, such as paroxetine, increase methadone blood concentrations. There is an up to 17-fold interindividual variation of methadone blood concentration for a given dosage, and interindividual variability of CYP enzymes accounts for a large part of this variation. Since methadone probably also displays large interindividual variability in its pharmacodynamics, methadone treatment must be individually adapted to each patient. Because of the high morbidity and mortality associated with opioid dependence, it is of major importance that methadone is used at an effective dosage in maintenance treatment: at least 60 mg/day, but typically 80-100 mg/day. Recent studies also show that a subset of patients might benefit from methadone dosages larger than 100 mg/day, many of them because of high clearance. In clinical management, medical evaluation of objective signs and subjective symptoms is sufficient for dosage titration in most patients. However, therapeutic drug monitoring can be useful in particular situations. In the case of non-response trough plasma concentrations of 400 microg/L for (R,S)-methadone or 250 microg/L for (R)-methadone might be used as target values.

Droperidol in the emergency department: is it safe?

Droperidol is an antipsychotic and antiemetic drug that has been used extensively by emergency physicians, psychiatrists, and anesthesiologists worldwide since 1967. It also has been used effectively for other diverse conditions, such as treatment of headache and vertigo. As of January 2001, Droperidol was no longer available in Europe after its founder, Janssen-Cilag Pharmaceuticals, discontinued its distribution. In December 2001, the United States Food and Drug Administration (FDA) placed a black box warning on the use of Droperidol in response to an association between Droperidol and fatal cardiac dysrhythmias, such as torsade de pointes, resulting from prolongation of the QT interval. In this review we closely examine the pharmacology, indications, use, and complications associated with Droperidol, and speculate on its future use in the Emergency Department.

Atypical antipsychotics in the treatment of bipolar disorder

Atypical antipsychotic medications are widely used for the treatment of bipolar disorder. Most empirical support suggests that these medications are efficacious in the treatment of acute mania, but there is considerably less support for the utility of these drugs in other phases of bipolar disorder. However, it is likely that several of these drugs will demonstrate efficacy in relapse prevention, and perhaps antidepressant efficacy in bipolar disorder as more studies are conducted. Atypical antipsychotics offer different side effect profiles than older antipsychotics, which may be of benefit for some patients. Consequently, atypical antipsychotics provide an important treatment option for bipolar patients.

Knowledge deficits related to the QT interval could affect patient safety

BACKGROUND

Recently, some QT-prolonging, noncardiac medications were withdrawn from the U.S. drug market because of continued inappropriate use by health care practitioners despite warnings and label changes from both the drug manufacturers and the U.S. Food and Drug Administration. This led us to assess the health care practitioners' knowledge of the QT interval and medications that may prolong it.

METHODS

We surveyed health care practitioners, primarily specialists in cardiology, to identify knowledge deficits related to the QT interval.

RESULTS

From a total of 334 survey respondents, 157 (47%) were physicians; 271 (81%) stated that cardiology was their area of specialization. Most of the respondents (86%) said that they would check an ECG before and after starting QT-prolonging medications, but less than half (42%) of all respondents and only 60% of physician respondents were able to accurately measure a sample QT interval on the survey. Less than two-thirds (63%) of respondents were able to accurately identify possible QT-prolonging medications, while only about half (51%) could accurately identify medication combinations that might prolong the QT interval.

CONCLUSIONS

We identified significant knowledge deficits regarding the QT interval and QT-prolonging medications. Additional research is needed to determine the extent to which these knowledge deficits may negatively affect patient safety. We must also develop effective strategies to eliminate these deficits.

Droperidol, QT prolongation, and sudden death: what is the evidence?

STUDY OBJECTIVE

Droperidol is a butyrophenone commonly used as an antiemetic and antipsychotic in the United States since US Food and Drug Administration (FDA) approval in 1970. Its labeling has recently been revised, with a black box warning for cases of QT prolongation leading to torsades de pointes and death. A black box warning is applied when serious adverse drug reactions are uncovered for medications. We sought to examine the evidence of a causal association suggested by the black box warning to aid clinicians in their risk-benefit analyses regarding further use of droperidol.

METHODS

A literature search was undertaken to determine the evidence regarding the association between droperidol and QT prolongation or torsades de pointes. The evidence was then evaluated by using evidence-based medicine principles. In addition, a review of the FDA regulatory process is presented.

RESULTS

Three clinical studies, 1 published abstract, and 7 case reports were reviewed. Available postmarketing surveillance data (MedWatch reports) were also reviewed. Applying the criteria of evidence-based medicine and Hill's criteria, the evidence is not convincing for a causal relationship between therapeutic droperidol administration and life-threatening cardiac events.

CONCLUSION

The recent black box warning appears to have originated from postmarketing surveillance data rather than data reported in the peer-reviewed medical literature. Ongoing monitoring of drug safety and more definitive study appear appropriate.

Concomitant use of antipsychotics and drugs that may prolong the QT interval

Concomitant use of drugs that prolong the QT interval is a risk factor for torsades de pointes, a ventricular arrhythmia associated with sudden death. This study compared the concomitant use of drugs that may prolong the QT interval ("other QT drugs") among two groups of patients: one that took antipsychotics that may prolong the QT interval (the QT antipsychotic group, n = 1,750) and one that used antipsychotics that do not result in QT prolongation (the non-QT antipsychotic group, n = 1,139). Data were pharmacy claim and eligibility information from January 1, 2000, through December 31, 2000, from a research database of a large pharmacy benefit manager. Concomitant use of antipsychotics and other QT drugs was examined for each participant over a 3- to 12-month follow-up period. Results showed that 51% of QT antipsychotic group members used other QT drugs concomitantly for at least 1 day in the follow-up period. Logistic regression indicated that there was no significant difference between the QT antipsychotic and non-QT antipsychotic groups with concomitant use of other QT drugs when potential confounders were controlled ( p = 0.6013). Although female sex is a risk factor for drug-induced torsades de pointes, women were more likely to concomitantly use other QT drugs than men in both the QT (56.2% vs. 43.2%; p < 0.001) and non-QT (53.1% vs. 43.0%;p < 0.001) antipsychotic groups. Findings suggest that the use of other QT drugs is not being minimized among patients taking QT antipsychotics.

Understanding the new and evolving profile of adverse drug effects in schizophrenia

This article has reviewed the emerging side-effect profiles of second-generation antipsychotic medications. Although these medications have favorable extrapyramidal side-effect profiles, clinicians must be aware of their propensity to cause weight gain, glucose and lipid abnormalities, and cardiac and sexual side effects. If clinicians are proactive about warning patients about these side effects and appropriately monitoring them, further morbidity and mortality may be prevented in this patient population. Initial choices of medication should be made based on the relative side-effect profiles in light of a particular patient's medical status. In the future, new treatments may be developed, with even fewer side effects.

Psychotropic drugs, cardiac arrhythmia, and sudden death

A variety of drugs targeted towards the central nervous system are associated with cardiac side effects, some of which are linked with reports of arrhythmia and sudden death. Some psychotropic drugs, particularly tricyclic antidepressants (TCAs) and antipsychotic agents, are correlated with iatrogenic prolongation of the QT interval of the electrocardiogram (ECG). In turn, this is associated with the arrhythmia (TdP). This review discusses the association between psychotropic agents, arrhythmia and sudden death and, focusing on TCAs and antipsychotics, considers their range of cellular actions on the heart; potentially pro-arrhythmic interactions between psychotropic and other medications are also considered. At the cellular level TCAs, such as imipramine and amitriptyline, and antipsychotics, such as thioridazine, are associated with inhibition of potassium channels encoded by In many cases this cellular action correlates with ECG changes and a risk of TdP. However, not all psychotropic agents that inhibit HERG at the cellular level are associated equally with QT prolongation in patients, and the potential for QT prolongation is not always equally correlated with TdP. Differences in risk between classes of psychotropic drugs, and between individual drugs within a class, may result from additional cellular effects of particular agents, which may influence the consequent effects of inhibition of repolarizing potassium current.

Antipsychotics and QT prolongation

OBJECTIVE

To evaluate literature relating to cardiac QT prolongation and the use of antipsychotic drugs.

METHOD

Literature searches of EMBASE, Medline, PsychLIT were performed in December 2001 and reference sections of retrieved papers scrutinized for further relevant reports.

RESULTS

The Cardiac QTc interval is difficult to measure precisely or accurately but appears to be a useful predictor of risk of dysrhythmia (specifically torsade de pointes) and sudden death. It is less clear that drug-induced QTc prolongation gives rise to similar risks but data are emerging, linking antipsychotic use to increased cardiac mortality. Many antipsychotics have been clearly associated with QTc prolongation. Methodological considerations arguably preclude assuming that any antipsychotic is free of the risk of QTc prolongation and dysrhythmia.

CONCLUSION

Available data do not allow assessment of relative or absolute risk of dysrhythmia or sudden death engendered by antipsychotics but caution is advised. Risk of dysrhythmia can very probably be reduced by careful prescribing of antipsychotics in low doses in simple drug regimens which avoid metabolic interactions. Electrocardiographic monitoring may also help to reduce risk but review by specialist cardiologist may be necessary.

Treatment recommendations for the use of antipsychotics for aggressive youth (TRAAY). Part II

OBJECTIVE

To develop treatment recommendations for the use of antipsychotic medications for children and adolescents with serious psychiatric disorders and externalizing behavior problems.

METHOD

Using a combination of evidence- and consensus-based methodologies, recommendations were developed in six phases as informed by three primary sources of information: (1) current scientific evidence (published and unpublished), (2) the expressed needs for treatment-relevant information and guidance specified by clinicians in a series of focus groups, and (3) consensus of clinical and research experts derived from a formal survey and a consensus workshop.

RESULTS

Fourteen treatment recommendations on the use of atypical antipsychotics for aggression in youth with comorbid psychiatric conditions were developed. Each recommendation corresponds to one of the phases of care (evaluation, treatment, stabilization, and maintenance) and includes a brief clinical rationale that draws upon the available scientific evidence and consensus expert opinion derived from survey data and a consensus workshop.

CONCLUSION

Until additional research from controlled trials becomes available, these evidence- and consensus-based treatment recommendations may be a useful approach to guide the use of antipsychotics in youth with aggression.

Death in bathtub revisited with molecular genetics: a victim with suicidal traits and a LQTS gene mutation

A 44-year-old woman with a medical history of mental disorders and previous suicidal behaviour was found in a bathtub and pronounced death few minutes later despite of resuscitation attempts. After police investigation and on the basis of autopsy findings, the death was classified as suicide drowning. Retrospective examination of clinical data revealed, a prolonged rate-corrected QT-interval (QTc: 468 ms) 3 months before death. Post-mortem (PM) DNA analysis disclosed KCNH2(FIN) mutation for the long-QT syndrome (LQTS). The value of PM molecular screening for LQTS is emphasised, especially for victims of putative drowning.

QTc interval lengthening is related to CYP2D6 hydroxylation capacity and plasma concentration of thioridazine in patients

Thioridazine cardiotoxicity has been associated with a prolonged heart-rate corrected QT (QTc) interval. However, no systematic studies have been performed on patients at therapeutic doses. The present study aimed to evaluate the influence of dose and plasma concentration of thioridazine and CYP2D6 enzyme status on the QTc interval in psychiatric patients. Sixty-five Spanish European psychiatric patients receiving thioridazine antipsychotic monotherapy were studied. The plasma levels of thioridazine and its metabolites were determined by high-performance liquid chromatography. All patients were phenotyped for CYP2D6 activity with debrisoquine during treatment. Thirty-five patients (54%) had a QTc interval over 420 ms. The lengthening of QTc interval was correlated with plasma concentration (p < 0.05) and daily dose (p < 0.05) of thioridazine. CYP2D6 enzyme hydroxylation capacity, evaluated by debrisoquine metabolic ratio (MR) (p < 0.05) and thioridazine/mesoridazine ratio (p < 0.05), was also correlated with QTc intervals. The present study shows the relationship between QTc interval lengthening among psychiatric patients treated at therapeutical doses with the dose and the plasma concentration of thioridazine. Since debrisoquine MR has been shown to be correlated with the QTc intervals, CYP2D6 enzyme hydroxylation capacity might be relevant in determining the risk for QTc interval lengthening. Patients with impaired CYP2D6 enzyme activity due to enzyme inhibition by thioridazine might be more prone to increased risk of sudden death due to torsade de pointes type cardiac dysrhythmia.

The potential cardiotoxicity of antipsychotic drugs as assessed by heart rate variability

Most antipsychotic drugs have cardiac effects as a consequence of their pharmacological actions. Recently, thioridazine has been subjected to a restricted indications notice and sertindole had its license withdrawn because of concerns about their potential cardiotoxicity. In the development of new atypical agents, heart-rate corrected QT effects are evaluated but it is unclear how predictive these are of clinically significant cardiotoxicity or sudden death. Heart rate variability (HRV) is a potential index of cardiotoxicity which has been found to be decreased following antidepressants and clozapine. We studied acute HRV changes following antipsychotic agents. Sixteen healthy male volunteers received risperidone (4 mg), olanzapine (10 mg), thioridazine (50 mg) or placebo in a randomized cross-over design. Subjective effects and psychomotor function were assayed at 2 h and both linear (summary statistics) and non-linear (scatterplot) measures of HRV were evaluated by continuous electrocardiogram recording over 10 h. Differential effects of single doses of the three antipsychotic drugs on HRV were found, and these were independent of their sedative effects. Olanzapine increased, and thioridazine decreased HRV, while risperidone had no effect. HRV is sensitive to the acute effects of antipsychotics. It may prove to be a reliable index of their potential for cardiotoxicity. Further studies in both healthy volunteers and patients on antipsychotic medication will be valuable.

Cardiac arrest and ventricular arrhythmia in patients taking antipsychotic drugs: cohort study using administrative data

OBJECTIVE

To examine the rates of cardiac arrest and ventricular arrhythmia in patients with treated schizophrenia and in non-schizophrenic controls.

DESIGN

Cohort study of outpatients using administrative data.

SETTING

3 US Medicaid programmes.

PARTICIPANTS

Patients with schizophrenia treated with clozapine, haloperidol, risperidone, or thioridazine; a control group of patients with glaucoma; and a control group of patients with psoriasis.

MAIN OUTCOME MEASURE

Diagnosis of cardiac arrest or ventricular arrhythmia.

RESULTS

Patients with treated schizophrenia had higher rates of cardiac arrest and ventricular arrhythmia than controls, with rate ratios ranging from 1.7 to 3.2. Overall, thioridazine was not associated with an increased risk compared with haloperidol (rate ratio 0.9, 95% confidence interval 0.7 to 1.2). However, thioridazine showed an increased risk of events at doses > or =600 mg (2.6, 1.0 to 6.6; P=0.049) and a linear dose-response relation (P=0.038).

CONCLUSIONS

The increased risk of cardiac arrest and ventricular arrhythmia in patients with treated schizophrenia could be due to the disease or its treatment. Overall, the risk with thioridazine was no worse than that with haloperidol. Thioridazine may, however, have a higher risk at high doses, although this finding could be due to chance. To reduce cardiac risk, thioridazine should be prescribed at the lowest dose needed to obtain an optimal therapeutic effect.

Safety of non-antiarrhythmic drugs that prolong the QT interval or induce torsade de pointes: an overview

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

Verapamil: new insight into the molecular mechanism of drug oxidation in the human heart

Verapamil is a commonly prescribed cardiovascular drug, but surprisingly its metabolism in the target tissue of pharmacotherapy is basically unknown. We therefore investigated its biotransformation in human heart tissue and correlate the production of metabolites with the gene expression of major drug metabolising enzymes. Using electrospray LC-MS-MS and LC-MS3 experiments, a total of nine metabolites were observed in incubation experiments with verapamil and microsomes isolated from the human heart tissue, and this included a carbinolamine-, N-formyl-, ahemiacetale-, and formate-intermediate of N-demethyl- and O-demethylverapamil. We also observed a hydroxylation product at the benzylic position of atom C-7 (M9). Metabolites M5-M9 are novel and were not observed in previous studies with liver or other human tissues. A fine example of the considerable metabolic competence of human heart is the formation of M1-M4, e.g. dealkylverapamil, norverapamil and isomers of O-demethylverapamil, which were believed to be exclusively produced by the liver.