Greater toxicity in overdose of dothiepin than of other tricyclic antidepressants

The cardiovascular safety of tricyclic antidepressants in overdose and in clinical use

Tricyclic antidepressants (TCAs) remain widely prescribed for depression and many other conditions. There may be important differences between individual TCA in regard to their overdose toxicity and their cardiac toxicity in clinical use. We conducted a systematic review to compare the toxicity of individual TCA in overdose and the risk of serious adverse cardiac events occurring with therapeutic doses. We used the fatal toxicity index (FTI) and case fatality ratio as markers of fatality in overdose, and hazard ratios or odds ratios for the risk of cardiovascular adverse events during normal clinical use. In all, 30 reports of mortality in overdose and 14 observational studies assessing the risk of cardiovascular adverse events in clinical use were included. FTI values were of the same order of magnitude (101-102) for all TCAs except lofepramine. Desipramine appears to be somewhat more likely than other TCAs to lead to death in overdose. Amitriptyline, clomipramine, dothiepin/dosulepin, doxepin, trimipramine and imipramine showed broadly similar toxicity and were usually reported to be less toxic than desipramine. Data on nortriptyline were contradictory. Lofepramine had the lowest risk of death in overdose. The rank order of overdose toxicity was broadly consistent between different FTI definitions and between markers used. With respect to the risk of cardiovascular events at clinically relevant exposure, amitriptyline, nortriptyline and lofepramine were associated with a greater risk of in-use cardiotoxicity. All measures of overdose toxicity were subject to external influences and confounding. The continued use of TCAs in depression and other conditions should be minimized when considering their undoubted toxicity in overdose and possible toxicity in normal clinical use.

Prevalence and patterns of anti-epileptic medication prescribing in the treatment of epilepsy in older adults with intellectual disabilities

BACKGROUND

The prevalence of epilepsy is higher in people with intellectual disability (ID) and increases with the degree of ID. Although life expectancy for people with ID is increasing, people with ID coexisting with epilepsy have a higher mortality rate, particularly those who had recent seizures. There have been few observational studies of the prevalence and patterns of anti-epileptic prescribing among older people with ID and epilepsy. The aim of this study was to investigate prevalence and patterns of anti-epileptic prescribing in the treatment of epilepsy in a representative population of older people with ID and epilepsy.

METHODS

This was an observational cross-sectional study from wave 1 (2009/2010) of Intellectual Disability Supplement to the Irish Longitudinal Study on Aging, a nationally representative sample of 753 persons with ID aged between 41 and 90 years. Participants and/or proxies recorded medicines used on a regular basis and reported doctor's diagnosis of epilepsy; medication data were available for 736 (98%). Prescribing of anti-epileptic drugs (AEDs) for epilepsy in those with a doctor's diagnosis of epilepsy (N = 205) was the primary exposure of interest for this study. Participant exposure to these AEDs was then categorised into AED monotherapy and polytherapy. Participants/carers reported seizure frequency, when epilepsy was last reviewed and which practitioner reviewed epilepsy. In addition, medications that may lower the seizure threshold that were listed in the Maudsley prescribing guidelines in psychiatry were examined.

RESULTS

Of the 736 participants with reported medicines use, 38.9% (n = 287) were exposed to AEDs, and 30.6% (225) had a doctor's diagnosis of epilepsy. Of those with epilepsy (n = 225), 90.9% (n = 205) reported concurrent use of AEDs and epilepsy. Of these 205 participants, 50.3% (n = 103) were exposed to AED polytherapy, and 63 different polytherapy regimes were reported. The most frequently reported AEDs were valproic acid (n = 100, 48.7%), carbamazepine (n = 89, 46.3%) and lamotrigine (n = 57, 27.8%). In total, 13.7% had a concurrent psychotropic, which should be avoided in epilepsy, and 32.6% had a psychotropic where caution is required. Antipsychotics with potential epileptogenic potential accounted for 80% of these medications. Of those with AED polytherapy (n = 103), 29.5% (28) reported being seizure free for the previous 2 years.

CONCLUSIONS

Prevalence of epilepsy was high among older people with ID, and half were exposed to two or more AEDs. Despite the use of AED therapy, over half had seizures in the previous 2 years. As the primary goals of optimal AED treatment are to achieve seizure freedom without unacceptable adverse effects, this was not achievable for many older patients with ID and epilepsy. Our findings indicated that people with ID and epilepsy were often exposed to psychotropic medications that may lower the seizure threshold. Regular review of epilepsy and medicines (including medicines that may interact with AEDs or lower the seizure threshold) by multidisciplinary teams working to agreed standards may improve quality of prescribing. Improved exchange of information and coordination of care between specialists and primary care practitioners in line with expert consensus recommendations could bring substantial benefit.

Lethal Tricyclic Antidepressant Overdose

Tricyclic antidepressant remains widely prescribed despite its dangerous cardiovascular and neurological effects in overdosed patients. We present a case of lethal dothiepin overdose and discuss the major complications and its management strategies.

Liposome supported peritoneal dialysis in rat amitriptyline exposure with and without intravenous lipid emulsion

Liposome supported peritoneal dialysis is a recently described technique which may eventually be applicable in the clinical scenario of the intoxicated patient. We evaluated the hypothesis that intravenous injection of lipid emulsion (ILE) would augment acidic pH gradient liposome supported peritoneal dialysis (LSPD). Orogastrically amitriptyline dosed rats were treated with either Sodium bicarbonate (NaHCO3) intravenously and standard intraperitoneal dialysate (Group A); NaHCO3 intravenously and LSPD (Group B); or ILE and LSPD (Group C). The primary endpoint was dialysate amitriptyline concentration after a 60 min dwell. Secondary analysis included an estimate of extraction ratio for peritoneal blood flow (ERs). There were significantly higher intraperitoneal concentrations of amitriptyline and ERs in the two groups treated with LSPD (Group B, p = 0.02, Group C, p < 0.01 vs. Group A). There was no observed effect for ILE on intraperitoneal amitriptyline concentration or ERs (p > 0.20). LSPD increased the amitriptyline concentration in peritoneal dialysate. No further increase was demonstrated with ILE. This may be either because such an effect is absent, or type II error. Exploratory analysis suggests LSPD may be driven by total rather than free drug concentrations.

Amitriptyline-induced ventricular tachycardia: a case report

Background

In Bangladesh, each emergency physician faces amitriptyline overdose nearly a day. An acute cardiovascular complication, one of the worst complications is mainly responsible for the mortality in tricyclic overdose. Recently, we managed ventricular tachycardia in a young female presented with an impaired consciousness 10 h after intentionally ingesting 2500 mg amitriptyline. Here, we report it, discuss how the electrocardiography is vital to acknowledge and predict it and its’ complications and also the recent update of the management of it.

Case presentation

A young married Bangladeshi-Bengali girl, 25-year-old, having a history of disharmony with her husband, came with an impaired consciousness after intentionally ingesting 2500 mg amitriptyline about 10 h before arrival. There was blood pressure 140/80 mmHg, heart rate 140 beats-per-min, temperature 103 °F, Glasgow coma scale 10/15, wide complex tachycardia with QRS duration of 178 ms in electrocardiography, blood pH 7.36. Initially, treated with 100 ml 8.4% sodium bicarbonate. After that, QRS duration came to 100 ms in electrocardiography within 10 min of infusion. To maintain the pH 7.50–7.55 over the next 24 h, the infusion of 8.4% sodium bicarbonate consisting of 125 ml dissolved in 375 ml normal saline was started and titrated according to the arterial blood gas analysis. Hence, a total dose of 600 mmol sodium bicarbonate was given over next 24 h. In addition to this, gave a 500 ml intravenous lipid emulsion over 2 h after 24 h of admission as she did not regain her consciousness completely. Afterward, she became conscious, though, in electrocardiography, ST/T wave abnormality persisted. So that, we tapered sodium bicarbonate infusion slowly and stopped it later. At the time of discharge, she was by heart rate 124/min, QRS duration 90 ms in electrocardiogram along with other normal vital signs.

Conclusion

Diagnosis of amitriptyline-induced ventricular tachycardia is difficult when there is no history of an overdose obtained. Nevertheless, it should be performed in the clinical background and classic electrocardiographic changes and wise utilization of sodium bicarbonate, intravenous lipid emulsion, and anti-arrhythmic drugs may save a life.

A prospective cohort study of trends in self-poisoning, Newcastle, Australia, 1987-2012: plus ça change, plus c'est la même chose

OBJECTIVE

To examine inhospital mortality and morbidity associated with self-poisoning with different drug classes over an extended period.

DESIGN, SETTING AND PARTICIPANTS

A prospective cohort study over 26 years (1987-2012) with limited follow-up of patients presenting consecutively to a primary and tertiary referral toxicology centre covering Newcastle, Lake Macquarie and Port Stephens, Australia.

MAIN OUTCOME MEASURES

Hospital length of stay, types of drugs ingested, intensive care unit (ICU) admission, requirement for ventilation, inhospital deaths and rates of antidepressant drug use in Australia.

RESULTS

Over the study period, there were 17 266 admissions of patients poisoned by 34 342 substances (16 723 drugs available only on prescription). The median length of stay was 16 hours, 12.2% of patients (2101/17 266) were admitted to an ICU, 7.4% (1281/17 266) were ventilated and 78 (0.45%) died in hospital. Patient demographics, social and psychiatric factors remained stable over the 26-year period, but case fatality decreased (from 0.77% [15/1955] to 0.17% [7/4060]) as did ICU admissions (19.2% [376/1955] to 6.9% [280/4060]), ventilation (13.7% [268/1955] to 4.8% [193/4060]) and LOS. The most frequently ingested substances were alcohol, benzodiazepines, paracetamol, antidepressants and antipsychotics. There was a substantial fall in some highly toxic drugs (tricyclic antidepressants, barbiturates, conventional antipsychotics and theophylline), but increases in less toxic selective serotonin reuptake inhibitors, serotonin-noradrenaline reuptake inhibitors and paracetamol. A greater than sixfold increase in community antidepressant use was accompanied by only minor changes in overall and antidepressant self-poisoning rates.

CONCLUSION

Over two decades, there were decreases in poisonings by many highly toxic drugs which were associated with substantial reductions in morbidity and inhospital deaths. Despite massive increases in the number of antidepressant prescriptions, neither rates of self-harm nor the proportion of antidepressant poisonings increased markedly.

Antidepressant overdose-induced seizures

Treating patients with psychiatric problems can present numerous challenges for clinicians. The deliberate self-ingestion of antidepressants is one such challenge frequently encountered in hospitals throughout the United States. This review focuses on 1) the classes of antidepressants, their pharmacologic properties, and some of the proposed mechanism(s) for antidepressant overdose-induced seizures; 2) the evidence for seizures caused by antidepressants in overdose; 3) management strategies for patients who have intentionally or unintentionally overdosed on an antidepressant, or who have experienced an antidepressant overdose-induced seizure.

Antidepressant overdose-induced seizures

Antidepressants are the most commonly prescribed class of medications in the United States. The clinician should be mindful of the many antidepressants that can produce seizures following an accidental exposure or an overdose. A broader understanding of the seizure potential of antidepressants, combined with the ability to recognize individuals at risk for a seizure after an overdose, can aid clinicians in determining the need for inpatient monitoring, and help facilitate their treatment decisions.

Toxicologists in public health--Following the path of Louis Roche (based on the Louis Roche lecture "An accidental toxicologist in public health", Bordeaux, 2010)

BACKGROUND

The global burden of clinical toxicology suggests a natural partnership with public health. This article reflects the content of a Louis Roche lecture given in 2010. HISTORICAL CONTEXT: Our practice and research in clinical toxicology has evolved from clinical cases to toxico-epidemiology to public health. This evolution in practice was initially unplanned but gained momentum and impact as we placed it more formally in a public health framework. This perspective is implicit in Louis Roche's call to "examine all aspects of the poisoning problem" and still provides a valuable starting point for any clinical toxicologist.

DISCUSSION

Clinical toxicology has always had a patient centered focus but its greatest successes have been related to public health interventions. Our early failures and later success in pubic health toxicology correlated with our understanding of the importance of partnerships outside our field. The most rapid dissemination and implementation of information derived from research occur through apriori partnerships with other agencies and international partners.

CONCLUSION

Addressing both local and global need has a number of bilateral synergies. Repositioning clinical toxicology into a public health framework increases access to strategic partnerships, research funds, and policy implementation while still addressing questions that are important to clinical practice.

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

OBJECTIVE

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

DESIGN

Population based observational study.

SETTING

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

PARTICIPANTS

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

RESULTS

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

CONCLUSIONS

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

Antidepressant drugs and cardiovascular pathology: a clinical overview of effectiveness and safety

OBJECTIVE

To review data examining the relationships between depression, antidepressants and cardiovascular disease.

METHOD

Structured searches of PubMed, Medline and Embase conducted in March 2008.

RESULTS

Depression and cardiovascular disease are closely associated clinical entities. Depression appears both to cause and worsen cardiovascular disease. Cardiovascular disease is in turn associated with a high incidence of depression. Depression is associated with increased mortality in cardiovascular disease, and after myocardial infarction (MI) and stroke. Many antidepressants have cardiotoxic properties. Tricyclic drugs are highly cardiotoxic in overdose and may induce cardiovascular disease and worsen outcome in established cardiovascular disease. Reboxetine, duloxetine and venlafaxine are known to increase blood pressure. Other antidepressants have neutral or beneficial effects in various cardiovascular disorders.

CONCLUSION

Sertraline, fluoxetine, citalopram, bupropion and mirtazapine appear to be safe to use after MI; the use of sertraline, and response to citalopram and mirtazapine may improve mortality. Paroxetine and citalopram appear to be safe to use in patients with established coronary artery disease. Limited data suggest that a variety of antidepressants are effective and safe to use after stroke.

[Intoxication with a tricyclic antidepressant]

A 48-year-old woman with a major depression and treatment with doxepin was found comatose in her flat. Her son last saw her 48 h prior to being found. On arrival of the emergency physician, she presented a generalized seizure. The patient underwent endotracheal intubation and mechanical ventilation due to respiratory insufficiency and severe cyanosis. Empty packages of tablets (doxepin ca. 4000 mg and zolpidem 100 mg) were found in the flat. On hospital admission the doxepin blood concentration was 1.2 microg/ml. No life-threatening arrhythmia occurred at any time. On the advice of the poison information center, hemoperfusion was performed for extracorporeal elimination. Within several hours the doxepin blood concentration could be lowered to 0.8 microg/ml and although still above the therapeutic range the patient was extubated. However, the patient developed a generalized seizure which required re-intubation. As a consequence of the high distribution volume and re-distribution phenomena, the doxepin blood concentration had increased again to 1.2 microg/ml. Approximately 72 h later she was extubated again while the doxepin blood concentration was 0.9 microg/ml and 3 days later, the doxepin blood concentration was lowered to 0.3 microg/ml and the patient was transferred to the psychiatric ward the following day. This case report questions the efficacy of hemoperfusion during acute doxepin intoxication in the given constellation of a non-life-threatening arrhythmia.

Seizure incidence in psychopharmacological clinical trials: an analysis of Food and Drug Administration (FDA) summary basis of approval reports

BACKGROUND

Clinical trial data provide an approach to the investigation of the effects of psychopharmacological agents, and psychiatric disorders themselves, on seizure threshold.

METHODS

We accessed public domain data from Food and Drug Administration (FDA) Phase II and III clinical trials as Summary Basis of Approval (SBA) reports that noted seizure incidence in trials of psychotropic drugs approved in the United States between 1985 and 2004, involving a total of 75,873 patients. We compared seizure incidence among active drug and placebo groups in psychopharmacological clinical trials and the published rates of unprovoked seizures in the general population.

RESULTS

Increased seizure incidence was observed with antipsychotics that was accounted for by clozapine and olanzapine, and with drugs indicated for the treatment of OCD that was accounted for by clomipramine. Alprazolam, bupropion immediate release (IR) form, and quetiapine were also associated with higher seizure incidence. The incidence of seizures was significantly lower among patients assigned to antidepressants compared to placebo (standardized incidence ratio = .48; 95% CI, .36- .61). In patients assigned to placebo, seizure incidence was greater than the published incidence of unprovoked seizures in community nonpatient samples.

CONCLUSIONS

Proconvulsant effects are associated with a subgroup of psychotropic drugs. Second-generation antidepressants other than bupropion have an apparent anticonvulsant effect. Depression, psychotic disorders, and OCD are associated with reduced seizure threshold.

Tricyclic antidepressant poisoning : cardiovascular toxicity

Tricyclic antidepressants remain a common cause of fatal drug poisoning as a result of their cardiovascular toxicity manifested by ECG abnormalities, arrhythmias and hypotension. Dosulepin and amitriptyline appear to be particularly toxic in overdose. The principal mechanism of toxicity is cardiac sodium channel blockade, which increases the duration of the cardiac action potential and refractory period and delays atrioventricular conduction. Electrocardiographic changes include prolongation of the PR, QRS and QT intervals, nonspecific ST segment and T wave changes, atrioventricular block, right axis deviation of the terminal 40 ms vector of the QRS complex in the frontal plane (T 40 ms axis) and the Brugada pattern (downsloping ST segment elevation in leads V1-V3 in association with right bundle branch block). Maximal changes in the QRS duration and the T 40 ms axis are usually present within 12 hours of ingestion but may take up to a week to resolve. Sinus tachycardia is the most common arrhythmia due to anticholinergic activity and inhibition of norepinephrine uptake by tricyclic antidepressants but bradyarrhythmias (due to atrioventricular block) and tachyarrhythmias (supraventricular and ventricular) may occur. Torsade de pointes occurs uncommonly. Hypotension results from a combination of reduced myocardial contractility and reduced systemic vascular resistance due to alpha-adrenergic blockade. Life-threatening arrhythmias and death due to tricyclic antidepressant poisoning usually occurs within 24 hours of ingestion. Rapid deterioration is common. Level of consciousness at presentation is the most sensitive clinical predictor of serious complications. Although a QRS duration >100 ms and a rightward T 40 ms axis appear to be better predictors of cardiovascular toxicity than the plasma tricyclic drug concentration, they have at best moderate sensitivity and specificity for predicting complications.

Medical management of deliberate drug overdose: a neglected area for suicide prevention?

OBJECTIVES

Overdoses account for a quarter of all suicides in England. The number of people who survive the immediate effects of their overdose long enough to reach medical attention, but who subsequently die in hospital is unknown. The aim of this study was to determine the proportion of overdose suicides dying in hospital and describe their sociodemographic characteristics.

METHOD

Cross sectional analysis of routinely collected Hospital Episode Statistics data for England (1997 to 1999) to identify hospital admissions for overdose among people aged 12+ and the outcome of these admissions.

RESULTS

Between 1997 and 1999 there were 233 756 hospital admissions for overdose, 1149 (0.5%) of these ended in the death of the patient such deaths accounted for 28% [corrected] of all overdose suicides and 8% [corrected] of total suicides. The median time between admission and death was three days (interquartile range one to nine days). The most commonly identified drugs taken in fatal overdose were paracetamol compounds, benzodiazepines, and tricyclic/tetracyclic antidepressants.

CONCLUSION

Around a quarter of all overdose suicide deaths occur subsequent to hospital admission. Further more detailed research is required to discover if better pre-admission and in-hospital medical management of those taking serious overdoses may prevent some of these deaths.

Tricyclic Antidepressant Poisoning

All tricyclic drugs are potentially able to cause the main acute CNS toxic syndromes of coma and convulsions. Dosulepin (dothiepin) seems more likely to cause convulsions than other drugs in this class, and amitriptyline also appears a more toxic tricyclic agent. Coma is the most useful sign indicative of toxic risk and appears to predict severe toxic complications (fits and arrhythmias) more reliably than ECG changes. Prophylactic therapy against convulsions has not been shown to be effective. Use of an anticholinesterase (physostigmine) is not recommended for management of coma. There is no good evidence base to support a particular anticonvulsant.

Australian and New Zealand clinical practice guidelines for the management of adult deliberate self-harm

BACKGROUND

The Royal Australian and New Zealand College of Psychiatrists is co-ordinating the development of clinical practice guidelines (CPGs) in psychiatry, funded under the National Mental Health Strategy (Australia) and the New Zealand Health Funding Authority.

METHOD

For these guidelines, the CPG Team for Deliberate Self-harm reviewed the treatment outcome literature (including meta-analyses) and consulted with practitioners and patients.

TREATMENT RECOMMENDATIONS

(i) Organization of general hospital services to provide: emergency department admission; a safe environment; integrated medical and psychiatric management; risk assessment; identification of psychiatric morbidity, and adequate follow-up. (ii) Detection and treatment of any psychiatric disorder. (iii) Dialectical behaviour therapy, psychoanalytically orientated partial hospitalization or home-based interpersonal therapy (for certain patients) to reduce repetition of deliberate self-harm (DSH).

CONCLUSION

Deliberate self-harm is common and is costly in terms of both individual distress and service provision. General hospitals are often the first point of clinical contact, but may not be appropriately organized to care for these patients. Evidence for the effectiveness of psychological treatments is based on single RCTs without replication. The three recommended psychological treatments are not widely available in Australia and New Zealand, and the interventions that are, such as cognitive behaviour therapy, problem solving and 'green cards' (an agreement guaranteeing access to services), do not reduce repetition of DSH. The effect of follow-up in psychiatric hospitals or in the community is poorly understood. We need to develop and evaluate interventions that will reduce repetition of both fatal and non-fatal deliberate self-harm and improve the person's functioning and quality of life.

A Meta‐Analysis of Prognostic Indicators to Predict Seizures, Arrhythmias or Death After Tricyclic Antidepressant Overdose

OBJECTIVES

To systematically review and summarize studies on the accuracy of ECG and tricyclic antidepressant (TCA) concentration as prognostic indicators of the risk of seizures, ventricular arrhythmia (VA) or death in patients with TCA overdose.

METHODS

Articles were identified with MedLine and Cochrane register of controlled clinical trials searches and review of medical toxicology textbooks. Quality of the included studies was assessed. Pooled estimates of sensitivity, specificity, likelihood ratios and Summary Receiver Operating Characteristics (SROC) curves were generated.

RESULTS

A total of 18 studies were included in the analysis. The pooled sensitivity (Se) and specificity (Sp) of the QRS for predicting seizures were 0.69 [95% CI 0.57-0.78] and 0.69 [95% CI 0.58-0.78] as compared to 0.75 [95% CI 0.61-0.85] and 0.72 [95% CI 0.61-0.81] for the TCA concentration. The Se and Sp of the QRS to predict VA were 0.79 [95% CI 0.58-0.91] and 0.46 [95% CI 0.35-0.59] compared to 0.78 [95% CI 0.56-0.90] and 0.57 [95% CI 0.46-0.67] for the TCA concentration. The Se and Sp of the QRS to predict death were 0.81 [95% CI 0.54-0.94] and 0.62 [95% CI 0.55-0.68] compared to 0.76 [95% CI 0.49-0.91] and 0.60 [95% CI 0.47-0.72] for the TCA concentration. Very few studies evaluated the accuracy of QTc, T 40 ms axis and the R/S ratio.

CONCLUSIONS

Overall, the studies suggested that the ECG and TCA concentration have similar but relatively poor performance for predicting complications, such as seizures, VA or death, associated with TCA overdose.

Relative Toxicity of Selective Serotonin Reuptake Inhibitors (SSRIs) in Overdose

BACKGROUND

Selective serotonin reuptake inhibitors (SSRIs) have increasingly replaced tricyclic antidepressants (TCAs) in the treatment of depression. They appear to be safer in overdose, but there is little information on their spectrum of toxicity in overdose, or relative toxicity of each agent.

OBJECTIVE

To determine the effect of SSRIs in overdose, as a group, and the relative toxicity of five different SSRIs.

METHODS

A review of consecutive SSRI poisoning admissions to a single toxicology unit. Outcomes examined were length of stay [LOS], intensive care [ICU] admission rate, coma, seizures, electrocardiographic [ECG] abnormalities, and presence of serotonin syndrome [SS]. Logistic regression was used to model the outcome QTc >440 msec.

RESULTS

There were 469 SSRI poisoning admissions analyzed after exclusions. The median LOS for all SSRI overdose admissions was 15.3 h (IQR: 10.5-21.3) and 30 of 469 (6.4%; 95% CI 4.3-9.0%) cases were admitted to ICU. The incidence of seizures was 1.9% and coma was 2.4%. Serotonin syndrome occurred in 14% of overdoses. Comparison of median QTc intervals of the five SSRIs was significantly different (p=0.0002); citalopram (450 IQR: 436-484) was individually different to fluoxetine (p=0.045), fluvoxamine (p=0.022), paroxetine (p=0.0002), and sertraline (p=0.001). The proportion of citalopram overdoses with a QTc >440 msec was 68%, differing significantly from sertraline (adjusted OR: 5.11 95% CI 2.32-11.27). Comparison of median QT intervals of the five SSRIs was statistically different (p=0.026); citalopram (400 IQR: 380-440) was individually different from sertraline (p=0.023).

CONCLUSIONS

This study shows SSRIs are relatively safe in overdose despite serotonin syndrome being common. The exception was citalopram, which was significantly associated with QTc prolongation. We believe that cardiac monitoring should be considered in citalopram overdose, particularly with large ingestions and patients with associated cardiac disease.

Shared mechanisms of antidepressant and antiepileptic treatments: drugs and devices

Many treatments for the epilepsies and affective disorder share the properties of seizure suppression and mood stabilization. Moreover, affective disorders and the epilepsies appear to share partially similar pathogenic mechanisms. A component of the shared predisposition appears to arise from noradrenergic and serotonergic deficits. Increasing evidence supports the hypothesis that noradrenergic and/or serotonergic elevation is a mechanism of therapeutic benefit shared by most antidepressants and many antiepileptic medications. Medication induced alterations in GABAergic, glutamatergic, and CRH (corticotropin releasing hormone) containing neurons may also contribute to the shared therapeutic properties of antidepressant and antiepileptic medications.

Assessing physostigmine's contraindication in cyclic antidepressant ingestions

Ingestion of cyclic antidepressant medications or prolongation of the electrocardiographic QRS interval are commonly considered as contraindications to the use of physostigmine as an antidote for antimuscarinic toxicity. This dictum seems to stem from a few well-publicized cases in which administration of physostigmine was temporally associated with the development of asystole. Before the report of these cases, physostigmine was more frequently used and had been considered a first-line antidote for both the neurologic and cardiac toxic effects of cyclic antidepressant overdose. This apparent inconsistency, and a resurgence of interest in physostigmine as an antidote, begs the question of the appropriateness of this drug's contraindication in all cyclic antidepressant ingestions. Review of the published clinical and experimental evidence provides little support for the clinical utility of using electrocardiographic criteria or the ingestion of cyclic antidepressants as contraindications to the use of physostigmine.

The limited utility of electrocardiography variables used to predict arrhythmia in psychotropic drug overdose

OBJECTIVE

The aim of the present study was to examine the relationship between serious arrhythmias in patients with psychotropic drug overdose and electrocardiography (ECG) findings that have been suggested previously to predict this complication.

METHODS

Thirty-nine patients with serious arrhythmias (ventricular tachycardia, supraventricular tachycardia or cardiac arrest) after tricyclic antidepressant overdose or thioridazine overdose were compared with 117 controls with clinically significant overdose matched to each case for the drug ingested. These patients with psychotropic drug overdose had presented for treatment to the Department of Clinical Toxicology, Newcastle and to the Princess Alexandra Hospital, Brisbane. The heart rate, the QRS width, the QTc and QT intervals, the QT dispersion, and the R wave and R/S ratios in aVR on the initial ECGs were compared in cases and controls.

RESULTS

The cases had taken dothiepin (16 patients), doxepin (six patients), thioridazine (five patients), amitriptyline (five patients), nortriptyline (three patients), imipramine (one patient) and a combination of dothiepin and thioridazine (three patients). In 20 of the 39 patients with arrhythmias, the arrhythmia had been a presumed ventricular tachycardia. Of the other 19 patients, 15 patients had a supraventricular tachycardia, two patients had cardiac arrests (one asystole, one without ECG monitoring) and two patients had insufficient data recorded to make classification of the arrhythmias possible. The QRS was >/= 100 ms in 82% of cases but also in 76% of controls. QRS >/= 160 ms had a sensitivity of only 13% and occurred in 2% of controls. QRS > 120 ms, QTc > 500 and the R/S ratio in aVR appeared to have a stronger association with the occurrence of arrhythmia: QRS > 120 ms (odds ratio [OR], 3.56; 95% confidence interval [CI], 1.46-8.68), QTc > 500 (OR, 3.07; 95% CI, 1.33-7.07), and R/S ratio in aVR > 0.7 (OR, 16; 95% CI, 3.47-74). Excluding thioridazine overdoses and performing the analysis for tricyclic antidepressant overdoses alone gave increased odds ratios for QRS > 120 ms (OR, 4.83; 95% CI, 1.73-13.5) and QTc > 500 (OR, 4.5; 95% CI, 1.56-13) but had little effect on that for the R/S ratio in aVR > 0.7 (OR, 14.5; 95% CI, 3.10-68).

CONCLUSION

ECG measurements were generally weakly related to the occurrence of arrhythmia and should not be used as the sole criteria for risk assessment in tricyclic antidepressant overdose. The frequently recommended practice of using either QRS >/= 100 ms or QRS >/= 160 ms to predict arrhythmias is not supported by our study. R/S ratio in aVR > 0.7 was most strongly related to arrhythmia but had estimated positive and negative predictive values of only 41% and 95%, respectively. The use of these specific predictors in other drug overdoses is not recommended without specific studies.

The toxicity of antidepressant poisoning: is it changing? A comparative study of cyclic and newer serotonin-specific antidepressants

AIM

To compare the clinical features of cyclic antidepressant and newer, non-cyclic, serotonin-specific antidepressant poisoning.

METHODS

Comparitive, descriptive study of all antidepressant overdose patients admitted to a hospital toxicology service from February 1997 to April 2001. Patient data were entered prospectively into a dedicated toxicology database for subsequent analysis.

RESULTS

There were 256 admissions for antidepressant poisoning (17.5% of all poisoning admissions). Cyclic antidepressant poisoning comprised 43% of antidepressant admissions. Statistically significant differences between the two groups included: cyclic antidepressant group had longer median length of stay (23.1 vs 15.9 h, P = 0.0008), greater need for endotracheal intubation (31%vs 4%, OR = 11.5, P < 0.0001) and higher incidence of seizures (7.2%vs 0.7%, OR = 10.4, P = 0.01), faster median pulse rate, longer QRS-interval on admission, and longer intensive care unit stays. However, non-cyclic, serotonin-specific antidepressant poisonings involved larger doses of antidepressants and were more likely to ingest other medications along with these. Serotonin syndrome was only seen in non-cyclic, serotonin-specific poisoning (10.3%, OR = 26.6, P = 0.0002). Patients with serotonin syndrome had a longer median hospital stay (46 vs 16 h, P < 0.0002) compared to other non-cyclic, serotonin-specific patients. There were no deaths during the study period.

CONCLUSIONS

Cyclic antidepressants still comprise a significant proportion of antidepressant poisoning and result in more significant morbidity than non-cyclic, serotonin-specific poisoning. Clinicians should also be aware that non-cyclic, serotonin-specific poisoning may result in the development of serotonin syndrome. This was the most significant toxic effect noted following non-cyclic, serotonin-specific poisoning in this study.

Diagnostic data in clinical toxicology--should we use a Bayesian approach?

A number of toxidromes (toxicology syndromes) have been described for various poisonings and are promoted as a means of reaching a diagnosis in patients presenting with unknown poisonings. Many are based entirely on deductive reasoning from the known pharmacological effects of these drugs rather than on documented clinical experience. In this paper, we used our database, where we have recorded clinical signs on presentation in unselected poisonings to explore how clinical signs actually alter the odds of ingestion of different poisons. Many signs substantially altered the list of drugs likely to have been ingested. We found that the most important factor determining whether an unconscious patient had ingested a particular drug was how frequently that drug was taken generally (i.e., the a priori probability), rather than the presence of any particular physical sign. It also follows that our (or anyone else's) intuitive or deductive approach to diagnosis, derived from experience, will not necessarily be very useful at another place where predominantly different drugs are involved in poisoning. Our data were used to derive odds ratios as a measure of the strength of association of physical signs or investigations with ingested poisons. These can be used to develop simple diagnostic algorithms orflow charts to identify the most likely drugs ingested, or using more complicated programming, could also be used to calculate the precise probability of different drug-ingestion using Bayes' Theorem. The usefulness (i.e., external validity) of clinical research from other centers can also be determined.

Data collection in clinical toxicology: are there too many variables?

The evidence base of clinical toxicology suffers in comparison to other clinical disciplines. There is an excess of case reports and case series with little in the way of case control or cohort studies, and very few randomized controlled trials. While randomized controlled trials are rightly regarded as the gold standard for interventional studies, they have limitations that are particularly evident in the practice of clinical toxicology. Properly conducted observational studies using quantitative, epidemiological methods [nonrandomized trials, cohort studies (prospective and retrospective), case control methods] can provide answers that may be impossible to obtain from randomized controlled trials. Development of a strong evidence base is essential for progress in clinical toxicology. Whether that evidence base is derived from randomized controlled trials or observational studies, it is essential to collect data. Important observations can be made from basic clinical data and systematic collection of those data into some form of electronic database has siginificant advantages. A clinical database provides accurate information in the areas of clinical practice, quality assurance (audit), and research. In the area of research, an appropriately designed database can be both a source of hypotheses as well as a vehicle to test them. It can also serve as a repository of research data in subsequent randomized controlled trials.

Antidepressants as risk factor for ischaemic heart disease: case-control study in primary care

OBJECTIVES

To determine whether antidepressants are a risk factor for ischaemic heart disease and to compare the risk for different subgroups of antidepressants and individual antidepressants.

DESIGN

Case-control study.

SETTING

Nine general practices recruited from the Trent Focus Collaborative Research Network.

PARTICIPANTS

933 men and women with ischaemic heart disease matched by age, sex, and practice to 5516 controls.

MAIN OUTCOME MEASURE

Adjusted odds ratio for ischaemic heart disease calculated by logistic regression.

RESULTS

Odds ratios for ischaemic heart disease were significantly raised for patients who had ever received a prescription for tricyclic antidepressants even after diabetes, hypertension, smoking, body mass index, and use of selective serotonin reuptake inhibitors had been adjusted for (1.56; 95% confidence interval 1.18 to 2.05). Patients who had ever taken dosulepin (dothiepin) had a significantly raised odds ratio for ischaemic heart disease after adjustment for confounding factors and use of other antidepressants (1.67, 1.17 to 2.36). There was no significant increase in the odds ratios for amitriptyline, lofepramine, and selective serotonin reuptake inhibitors in multivariate analysis. Increasing maximum doses of dosulepin were associated with increasing odds ratios for ischaemic heart disease. Similarly, there was a significant positive trend associated with increasing numbers of prescriptions of dosulepin (adjusted odds ratio 1.52 for 1 prescription, 1.39 for 2-3, and 1.96 for >/=4, P<0.002).

CONCLUSION

There is good evidence for an association between dosulepin and subsequent ischaemic heart disease and for a dose-response relation.

Tricyclic antidepressant overdose: a review

Overdoses of tricyclic antidepressants are among the commonest causes of drug poisoning seen in accident and emergency departments. This review discusses the pharmacokinetics, clinical presentation and treatment of tricyclic overdose.

Epilepsy, depression and antidepressant drugs

Apart from constituting an important management problem, depression coexisting with epilepsy is also an interesting psychiatric phenomenon, with multiple interacting biological, psychological and social factors involved in its causation. New research approaches to the study of epilepsy and depression, including neuroimaging, neurochemical and neuroendocrine techniques, and the arrival of new classes of antidepressants in recent years, suggest it is timely to reconsider this topic. We review current knowledge of the prevalence and causes of interictal depression in epilepsy, focussing mainly on neurobiological factors, and give an overview of recent concepts concerning the management of depression. We also discuss pharmacological treatment of depression in epilepsy, focussing on the association between antidepressants and seizures, and drug interactions.

Suicide by antidepressant intoxication identified at autopsy in Vienna from 1991-1997: the favourable consequences of the increasing use of SSRIs

In the area of Vienna, any person dying under questionable circumstances is examined at the Institute of Forensic Medicine, where the cause of death is determined by means of autopsy and chemical analysis. Our study on fatal intoxications was performed in the period between 1991 and 1997, when selective serotonin reuptake inhibitors (SSRIs) were establishing themselves on the market, reaching the top of prescription statistics. Tricyclic antidepressants (TCAs) were involved in 30 single- and 127 multiple-substance intoxications, with amitriptyline and doxepin being the most frequently used drugs. SSRIs were involved in five multiple-substance intoxications. The f-value, which refers to the number of deaths per million defined daily doses prescribed, was found to be significantly (P</=0.001) higher in TCAs than in SSRIs. The f-value for the total group of all antidepressants declined significantly (P</=0.05) during the observation period of 7 years. In conclusion, SSRIs turned out to be less toxic than TCAs, and the increasing use of new antidepressants did not coincide with an increased number of deaths caused by these drugs.

Depression in epilepsy: etiology, phenomenology, and treatment

A history of depression or depressive symptomatology has been reported in up to two-thirds of patients with medically intractable epilepsy, whereas community studies have demonstrated affective disorder only in a quarter of these patients. Depression has been reported peri- and interictally. However, differentiation may be difficult in patients with frequent seizures. Most authors have found no correlation between depression and epilepsy variables. However, complex partial seizures, especially of temporal lobe origin, appear to be etiologic factors, particularly in men with left-sided foci. Depression is also more common in patients treated with polytherapy especially with barbiturates, phenytoin, and vigabatrin. Depression has also been described de novo after temporal lobectomy. Psychosocial factors also play a part, but underlying risk factors (e.g., genetic, endocrine and metabolic) may explain the increased rates of depression in people with epilepsy compared to those with other neurologic and chronic medical conditions. The depression appears to be endogenous. Patients tend to exhibit fewer neurotic traits and more psychotic symptoms such as paranoia, delusions, and persecutory auditory hallucinations. Treatment approaches include psychotherapy, rationalization of antiepileptic drug medication, antidepressant treatment, and ECT. The tricyclic and related antidepressants appear to be epileptogenic, especially in people at high risk (personal or family history of seizures, abnormal pretreatment EEG, brain damage, alcohol or substance abuse/withdrawal and concurrent use of CNS-active medication). Seizures tend to occur early in treatment or after dose increments, especially if rapidly titrated. There is little evidence that the newer antidepressants, e.g., selective serotonin reuptake inhibitors, moclobemide, venlafaxine, or nefazodone are more epileptogenic than placebo.

Effects of dothiepin on delayed conduction produced by ventricular arrhythmia in the canine heart after myocardial infarction

1. In order to clarify the arrhythmogenic effects of antidepressants, the authors examined the effects of dothiepin and amitriptyline on the ventricular activation time (VAT), effective refractory periods(ERP) and incidence of arrhythmias induced by programmed electrical stimulation(PES) in the dog heart in situ after myocardial infarction. 2. Myocardial infarction was produced by two-stage ligation of the left anterior descending coronary artery. Seven days after ligation, bipolar electrodes were sutured on the ventricular surface of the infarcted and normal zones to apply an electrical stimulation or record ventricular activation. An electrical stimulation with coupling interval 250 or 180 ms was applied on the ventricular surface, and AT was measured. 3. Dothiepin at doses of 1-3 mg/kg increased the heart rate. The VAT of coupling interval 180 ms in the infarcted zone was increased by the administration of 3 mg/kg dosulepin. Dothiepin at 3 mg/kg increased the incidence of ventricular arrhythmias induced by PES. 4. Amitriptyline, at doses of 1-3 mg/kg, significantly increased the heart rate. Amitriptyline increased the VAT dose- and frequency-dependently(2,3 mg/kg zone), and prolonged the ERP and QT c interval. Amitriptyline at doses of 1-3 mg/kg increased the incidence of ventricular arrhythmias by PES. 5. These results indicate that dothiepin, 1-3 mg/kg, has lesser effects on cardiac delayed conduction produced by ventricular arrhythmia than amitriptyline.

Can the fatal toxicity of antidepressant drugs be predicted with pharmacological and toxicological data?

Antidepressant drugs are among the most common drugs involved in fatal poisoning and large variations between antidepressant drugs have been noted. Despite the fact that a large number of studies have calculated a fatal toxicity index (FTI) for antidepressants, no serious attempts have been made to compare the differences in fatal toxicity against known pharmacological and toxicological differences in receptor affinity. It is potentially from such data that screening of drugs during their pre-clinical development can be facilitated. We examined correlations between the FTI and noradrenaline (norepinephrine)/serotonin (5-hydroxytryptamine; 5-HT) reuptake inhibition selectivity, the dose that is lethal to 50% of animals (LD50), lipid solubility, and antagonist activity at cholinergic, histaminergic, alpha-adrenergic and gamma-aminobutyric acid (GABA)A receptors or sodium and potassium channel blocking effects. We obtained data on the number of fatal poisonings between 1983 and 1992 in England and Wales caused by a single antidepressant drug from the Department of Health in the UK. This number was divided by the number of prescriptions in England for these drugs over this time to derive a FTI of deaths per million prescriptions. The highest FTIs were for amoxapine, viloxazine, desipramine and dothiepin. Lofepramine, paroxetine and fluoxetine had very low FTIs. Using Poisson regression, there was a significant positive relationship between the FTI of antidepressant drugs and their lethal toxicity in animals, and measures of their cardiac effects. The relative noradrenaline/serotonin reuptake inhibition, lipid solubility and their potency at histamine H1, muscarinic and alpha 1-adrenergic receptors had no substantial association with the FTI. Limited data suggest that some cardiac effects and potency as a GABAA antagonist may be important predictors of significant toxicity. Further data using standardised bio-assays are needed to compare the direct cardiac effects of antidepressants. Thus, the best current pre-clinical indicator of fatal toxicity in humans is the LD50 in animal studies. Clearly, there are humane and practical reasons for developing a better pre-clinical indicator of toxicity in overdose for this rapidly expanding group of drugs.

Poisoning and epidemiology: 'toxicoepidemiology'

1. There is little hypothesis-testing clinical research performed in toxicology. Randomized clinical trials are rare and most observational studies are performed on highly selected patients and are subject to marked bias. Thus, for many poisonings, our approach has been based almost entirely on deduction from known pharmacological/toxicological effects, generalizations from drugs within the same therapeutic class, animal data and case reports. This is also far from satisfactory, as many toxicological mechanisms are poorly understood and not related to the therapeutic class. 2. Although we need much better data to address the clinical and public health aspects of poisoning, there are many practical and ethical reasons why randomized clinical trials are difficult in this field. However, the scope for observational research, in particular population-based clinical epidemiology, is almost unlimited. The collection of data on human poisoning is facilitated because most non-fatal overdoses are admitted to hospital and by legal requirements to report to the coroner deaths that are due to poisoning. In the present article I argue that 'toxicoepidemiology', meaning the application of epidemiological methods to the problem of acute poisoning, is the best means we have of addressing deficiencies in our knowledge of poisoning. 3. Examples are given of a variety of observational research strategies, ranging from audit to meta-analysis, that may be applied to clinical toxicology. From coronial and clinical data obtained from reasonably well-defined populations, it has been possible to identify a number of previously unrecognized differences in the severity and spectrum of toxicity between and within drug classes. Also, the demographic risk factors for poisoning and the reproducibility, validity and optimal use of diagnostic and therapeutic interventions can be assessed. 4. The major limitations to the range of associations and interventions that may be studied are the need to achieve adequate power to study uncommon outcomes or poisonings and the ability to replicate findings at other centres using similar methodology. The expansion of data collection to other centres has the potential largely to overcome these obstacles.

Health care. A model for the management of self-poisoning

OBJECTIVE

To describe the development and activity of a multidisciplinary service to manage self-poisoning.

DESIGN

Descriptive, comparative study with prospective data collection.

SETTING

Regional toxicology treatment centre in the Hunter area of New South Wales (NSW) with primary and secondary referral service to 385,000 people and tertiary referral service to a further 100,000.

PATIENTS

All patients (1987-1995) with poisoning or envenomation presenting to the Hunter Area Toxicology Service (HATS).

MAIN OUTCOME MEASURES

Average length of stay for HATS compared with national and NSW hospitals; mortality data for HATS compared with NSW.

RESULTS

Average length of stay for HATS was 0.53-1.22 days shorter than for all Australian hospitals, potentially saving 518 bed-days, valued at $468,000 per year. Average length of stay was 0.94-3.39 days shorter than for all NSW hospitals, saving 1470 bed-days at $1.4 million per year. Inpatient mortality (0.2%; 95% confidence interval, 0.0-1.1) was not significantly different from NSW (0.5%; 95% CI, 0.2-0.8). Standardised mortality ratios showed no greater all-cause suicide mortality.

CONCLUSIONS

In our centralised model for managing self-poisoning, all toxicology patients in an area health service are diverted to one hospital, where all patients with deliberate self-poisoning are admitted under the one multidisciplinary team, and all receive psychiatric assessment. This model has substantially reduced bed stay, with considerable savings to the Hunter Area Health Service manifested as an increase in beds available for other purposes.

Epidemiology and relative toxicity of antidepressant drugs in overdose

Antidepressant drugs are currently the mainstay of treatment for all but the mildest forms of depression. Their effectiveness in the management of depressive illness is undisputed and their effectiveness in preventing suicide, while not proven, may be assumed. Nevertheless, of all the drugs that are taken in lethal overdose, prescribed antidepressants are among the most common. Epidemiological studies from several countries have provided evidence of marked differences in overdose toxicity between drug classes and, in some cases, between individual drugs within a class, with some of the older tricyclic antidepressants (TCAs) being the most toxic. Over 80% of all deaths arising from overdose of antidepressant medication in the UK between 1987 and 1992 were caused by 2 drugs: amitriptyline and dothiepin. Taken alone, this figure conveys little information about the toxicity of either drug. However, when considered within an epidemiological context, the evidence suggests that both drugs are highly toxic in overdose, a conclusion that is supported by animal studies of the toxicity of TCAs and by clinical evidence of overdose toxicity. This paper reviews the epidemiological evidence concerning the acute toxicity of antidepressant drugs and considers the interplay of factors that contribute to the toxicity which occurs when they are taken in acute overdose. The inherent toxicity of the drug appears to be the crucial factor and, although less well researched, prescribing practices and perception of toxicity are probable contributory factors.

Antidepressant deaths by overdose

OBJECTIVE

To determine the prevalence of antidepressant deaths in South Australia, the relative frequency of each antidepressant used and demographic data of those who died.

METHOD

This was a retrospective, case note study of all cases where death was caused by lethal levels of antidepressants in South Australia for the period from 1986 to 1990. The study occurred at the South Australian coroner's office. Subjects were selected from toxicology data, where serum or liver levels of one or more antidepressant were in the lethal range.

RESULTS

Seventy-one cases were identified and information was obtained on 68 of these cases from the coroner's files. Amitriptyline, Doxepin and Dothiepin accounted for the majority of antidepressant deaths. Women were 2.5 times more likely to use antidepressants to suicide than men. At least 63% had a known psychiatric illness and 45% had previously attempted suicide.

CONCLUSIONS

The older tricyclic antidepressants are a significant cause of suicide. It is recommended that the newer antidepressants, which are as efficacious yet safer in overdose, be prescribed in preference to the older tricyclic antidepressants, as the first line of treatment in newly diagnosed depressed outpatients.

An analysis of age and gender influences on the relative risk for suicide and psychotropic drug self-poisoning

Psychiatric illness is a significant risk factor for both attempted and completed suicide and psychotropic medications account for 80% of all drug overdoses involving prescription medications. One challenge facing clinicians is to balance the benefit of treatment against the risk of drug overdose. The aim of the present study was to compare the age and gender distribution of patients prescribed psychotropic drugs with patients attempting and completing suicide with these drugs. Data were obtained from the Australian census and studies of general practitioner prescribing, patients who committed suicide or presented with self-poisoning within a defined geographic area. The characteristics of these populations were compared to calculate odds ratios for attempting or completing suicide with psychotropic drugs, before and after correction for rates of prescription, in different age and gender groups. The odds ratios (ORs) for self-poisoning were higher for those aged less than 45 years and yet this group was least likely to be prescribed psychotropic drugs. Men had a much higher rate of completed suicide using more lethal methods. The ORs for self-poisoning and suicide with psychotropic drugs, after correction for prescription rates, for those aged 15 to 24 years were 11.1 and 1.7, respectively. Those aged 25 to 44 years had ORs of 4.9 and 4.3, and, by contrast, those over 75 years had ORs of 0.03 and 0. Women were slightly more likely to poison themselves with psychotropic drugs (OR 1.2). However, the situation reversed after correction for prescription rates (OR 0.69). It is concluded that greater caution should be exercised in prescribing for those under 45 years of age, given their relatively higher risk of drug overdose, and that the least toxic compounds should be used. The risk (of self-poisoning) among the elderly may have been overstated, so that some patients may have been denied the benefit of adequate treatment.

The treatment of depression: prescribing patterns of antidepressants in primary care in the UK

BACKGROUND

Consensus has been achieved about how depression should be treated in primary care, and guidelines have been issued by the Royal Colleges of General Practitioners and Psychiatrists, and by the British Association for Psychopharmacology. One of the principal recommendations is to prescribe antidepressant medicine at effective doses. This study was established to investigate how current prescribing practices in primary care compared with these guidelines.

METHOD

Information on prescribing of antidepressant medicines was obtained using three independent data sources: Prescribing Analysis and Cost (PACT) data; medical notes; and a large, computerised patient record database.

RESULTS

Data were obtained on populations in excess of 1.5 million people, and over 80,000 prescriptions were reviewed. All three data sources showed very similar patterns of prescribing, in particular that as many as 88% of prescriptions for older tricyclic antidepressants are prescribed by GPs at doses below those recommended by the consensus guidelines. Newer antidepressants-lofepramine and the SSRIs-are prescribed comparatively well.

CONCLUSIONS

Prescribing of antidepressants by GPs is not in line with the consensus recommendations on dosage. This may have major educational implications for GPs. A pragmatic approach to improve prescribing in the short term may be to advocate the use of lofepramine or the SSRIs as first line treatment for depression. This study validates the use of PACT data as a useful audit tool in this area of clinical practice.

A fatal dothiepin overdose

High pressure liquid chromatography coupled to photodiode array detector and capillary gas chromatography coupled to mass spectrometry were employed to quantify dothiepin in biological fluids, tissues and hair in a death attributed to oral dothiepin (Prothiaden) ingestion. The blood concentration of dothiepin was 5.75 mg/l. Hair analysis clearly indicated a chronic antidepressant exposure, with a dothiepin concentration of 1.89 ng/mg hair. Results are discussed in the light of the existing literature.