Hospital usage of TOXBASE in Great Britain: Temporal trends in accesses 2008 to 2015

AIM

To examine temporal trends in accesses to the UK's National Poison Information Service's TOXBASE database in Britain.

METHODS

Generalized additive models were used to examine trends in daily numbers of accesses to TOXBASE from British emergency departments between January 2008 and December 2015. Day-of-the-week, seasonality and long-term trends were analysed at national and regional levels (Wales, Scotland and the nine English Government Office Regions).

RESULTS

The long-term trend in daily accesses increases from 2.8 (95% confidence interval (CI): 2.6-3.0) per user on 1 January 2008 to 4.6 (95% CI: 4.3-4.9) on 31 December 2015, with small but significant differences in population-corrected accesses by region ( p < 0.001). There are statistically significant seasonal and day of the week patterns ( p < 0.001) across all regions. Accesses are 18% (95% CI: 14-22%) higher in summer than in January and at the weekend compared to weekdays in all regions; there is a 7.5% (95% CI: 6.1-8.9%) increase between Friday and Sunday.

CONCLUSIONS

There are consistent in-year patterns in access to TOXBASE indicating potential seasonal patterns in poisonings in Britain, with location-dependent rates of usage. This novel descriptive work lays the basis for future work on the interaction of TOXBASE use with emergency admission of patients into hospital.

Circulating acetaminophen metabolites are toxicokinetic biomarkers of acute liver injury

Acetaminophen (paracetamol-APAP) is the most common cause of drug-induced liver injury in the Western world. Reactive metabolite production by cytochrome P450 enzymes (CYP-metabolites) causes hepatotoxicity. We explored the toxicokinetics of human circulating APAP metabolites following overdose. Plasma from patients treated with acetylcysteine (NAC) for a single APAP overdose was analyzed from discovery (n = 116) and validation (n = 150) patient cohorts. In the discovery cohort, patients who developed acute liver injury (ALI) had higher CYP-metabolites than those without ALI. Receiver operator curve (ROC) analysis demonstrated that at hospital presentation CYP-metabolites were more sensitive/specific for ALI than alanine aminotransferase (ALT) activity and APAP concentration (optimal CYP-metabolite receiver operating characteristic area under the curve (ROC-AUC): 0.91 (95% confidence interval (CI) 0.83-0.98); ALT ROC-AUC: 0.67 (0.50-0.84); APAP ROC-AUC: 0.50 (0.33-0.67)). This enhanced sensitivity/specificity was replicated in the validation cohort. Circulating CYP-metabolites stratify patients by risk of liver injury prior to starting NAC. With development, APAP metabolites have potential utility in stratified trials and for refinement of clinical decision-making.

Poisons information in Scotland: delivery of TOXBASE on the Internet

Poisons information in the UK is provided by the six centres of the National Poisons Information Service (NPIS). In mid-1999 an existing database, TOXBASE, was modernized and transferred to the Internet and made freely available to health professionals working in the National Health Service. We report the effect of this change on poisons information provision in Scotland in 2000.

Telephone and TOXBASE enquiry profiles and agent accesses, were examined by enquirer source and Scottish Health Board (corrected for population size). Indices used included number of telephone enquiries and computer usage data, including details of agent and agent category.

Enquiries to TOXBASE were found to be more than 3.4 times more frequent than by telephone. Profile of agents was generally similar, apart primarily from ethanol, which was a more frequent telephone agent. There was a negative correlation between population-corrected volume of telephone enquiries and TOXBASE sessions by the health board. Most telephone enquiries came from primary care, whereas the major TOXBASE users were Accident and Emergency (A and E) departments. Referrals to senior clinical staff increased from the previous year.

Our study concluded that computer information systems are alternative tools to the telephone for poisons information provision. In Scotland there is evidence that the systems complement each other, with no evidence of loss of clinical referrals about more severe poisoning. User feedback has been positive.

Olanzapine overdose is associated with acute muscle toxicity

Olanzapine is an atypical antipsychotic that is reported to cause myopathy and raised creatine kinase (CK) levels. The prevalence and severity of acute myopathy after deliberate olanzapine ingestion are unclear. Therefore, we reviewed casenotes from 64 consecutive patients admitted to our institution after olanzapine overdose. Overall, serum CK was higher than five times the upper limit of normal in 17% of patients. The prevalence of raised CK values was positively correlated with the stated quantity of olanzapine ingested, suggesting a dose-dependent relationship for acute muscle toxicity. There was an apparent delay of 12 hours or more between olanzapine ingestion and the occurrence of maximum CK. Despite the high prevalence of acute muscle toxicity after olanzapine ingestion, none of the patients developed renal failure.

Poisons admissions in Edinburgh 1981-2001: agent trends and predictors of hospital readmissions

Self-poisoning is a major public health problem. This study describes patterns of admissions and readmissions from self-poisoning to the Royal Infirmary of Edinburgh from 1981 to 2001. A database on hospital discharges with a diagnosis (ICD-9/10) of poisoning between 1981 and 2001 was used. Annual admissions were described for seven main drug categories, and proportions of patients readmitted within 1-5 years from first admission, were computed for each category. Cox proportional hazards regression was used to evaluate prognostic factors for readmission risk over 1981-2001. For both sexes, admissions increased from the early to mid 1990s, and declined thereafter. The proportion readmitted varied with the drug taken at first admission, from 11.9% (95% CI: 10.8-13%) for non-opiate analgesics, to 17.6% (16.5-18.7%) for benzodiazepines. Deprivation was positively related to readmission risk after first admissions with paracetamol (P<0.001) and benzodiazepines (P<0.001). Timing of first admissions involving paracetamol (P<0.01), benzodiazepines (P<0.001), antidepressants (P<0.001), non-opiate analgesics (P<0.001), and opiates (P<0.05), was inversely associated with readmission risk. In patients admitted for drug overdose, readmission risk is influenced by type of drug taken at first admission. Information on drug type used in self-poisoning may assist in identifying patients at risk for future events, and in reducing hospital read-missions.

Impact of reducing the threshold for acetylcysteine treatment in acute paracetamol poisoning: the recent United Kingdom experience

BACKGROUND

On 3 September 2012, the licensed indication for acetylcysteine was changed in the United Kingdom (UK) so that all patients with a plasma paracetamol concentration above a "100 mg/L" (4 h post ingestion) nomogram treatment line after an acute paracetamol (acetaminophen) overdose should be treated. This is a lower threshold than that used in the United States, Canada, Australia, and New Zealand. Here we report the impact of this change in the UK on the management of patients with acute overdose in different paracetamol concentration ranges.

METHODS

This is a cohort study, consisting of a retrospective analysis conducted on prospectively collected audit data in three UK hospitals. Following appropriate ethical and data protection authority approval, data for patients presenting within 24 h of an acute timed single paracetamol overdose were extracted. Numbers of admissions and use of antidote in relation to different paracetamol concentration bands (< 100 mg/L; 100-149 mg/L; 150-199 mg/L; and ≥ 200 mg/L at 4 h) were analyzed for one-year periods before and after the change.

RESULTS

Comparing the year before with the year after the change, there was no change in the numbers of patients presenting to hospital within 24 h of acute timed paracetamol overdose (1246 before and 1251 after), but more patients were admitted (759 before and 849 after) and treated with acetylcysteine (389 before and 539 after). Of the 150 additional patients treated with acetylcysteine in the year following the change, 114 (76%, 95% CI: 68.4-82.6) were in the 100-149 group and 9 (6.0%, 95% CI: 2.8-11.1) in the 150-199 group.

CONCLUSIONS

Changes to national guidelines for managing paracetamol poisoning in the UK have increased the numbers of patients with acute overdose treated with acetylcysteine, with most additional treatments occurring in patients in the 100-149 mg/L dose range, a group at low risk of hepatotoxicity and higher risk of adverse reactions.

Guidelines for laboratory analyses for poisoned patients in the United Kingdom

To enable consistency of investigation and the establishment of best practice standards, consensus guidelines were formulated previously by the UK National Poisons Information Service and the Association for Clinical Biochemistry. These joint guidelines have now been updated to reflect current best practice. The types of laboratory investigation required for poisoned patients are categorized as either (a) essential common laboratory investigations or (b) specific toxicological assays, and also as either (i) common or (ii) specialist or infrequent. Tests in categories (a) and (bi) should be available 24 hours per day, with a maximum turnaround time of 2 h. For the specialist assays, i.e. category (bii), availability and turnaround times have been specified individually. The basis for selection of these times has been clinical utility. The adoption of these guidelines, along with the use of the National Poisons Information Service (0844 8920111) and its online poisons information resource TOXBASE(®) (www.toxbase.org) enable the poisoned patient to receive appropriate, 'best practice' investigations according to their clinical needs and will avoid unnecessary investigations.

The predictive value of hospital admission serum alanine transaminase activity in patients treated for paracetamol overdose

BACKGROUND

Paracetamol is a major cause of poisoning. Treatment decisions are predominately based on the dose ingested and a timed blood paracetamol concentration because most patients present to hospital soon after overdose, before hepatotoxicity can be confirmed/excluded using serum alanine transaminase (ALT). Nonetheless, ALT is measured at hospital presentation; we investigated its value in predicting hepatotoxicity.

METHODS

From March 2011 to May 2012, patients admitted to the Royal Infirmary of Edinburgh for paracetamol overdose treatment were identified. We determined the value of admission ALT (below or above our upper limit of normal-50 IU/l) at predicting three endpoints: 1-doubling of ALT; 2-peak ALT >1000 IU/l; 3-peak international normalized ratio (INR) >2.

RESULTS

From 500 patients, 410 met the entry criteria; 264 presented within 8 h of overdose, 54 between 8 and 24 h, 53 after 24 h and 39 were staggered ingestions. Admission ALT was increased in 71. For endpoint 1 (ALT doubling), the positive predictive value (PPV) of admission ALT was 19% [95% confidence interval (CI) 12-30] with a negative predictive value (NPV) of 98% (95% CI 96-99); endpoint 2 (ALT >1000 IU/l: PPV 23% (95% CI 14-34) and NPV 100% (95% CI 99-100) and for endpoint 3 (INR >2): PPV 14% (95% CI 7-25) and NPV of 100% (95% CI 99-100). The NPV remained high when only late presenters were included.

CONCLUSION

Admission ALT within the normal range has a high NPV and could be used, alone or in combination with newer biomarkers, to identify lower risk patients at hospital presentation.

UK childhood exposures to pesticides 2004-2007: a TOXBASE toxicovigilance study

OBJECTIVE

There are no systematic methods for toxicovigilance of non-medicinal products in the UK. This is particularly relevant for pesticides, where there is significant public concern about potential adverse effects. This study describes a prospective toxicovigilance scheme based on follow-up of enquiries to the National Poisons Information Service (NPIS) through its online poisons information system TOXBASE. These enquiries reflect acute exposures and the patterns of acute illness that result.

RESULTS

A total of 10 061 pesticide-related enquiries were identified. After follow-up, data were gathered on 2364 suspected exposures, of which 1162 involved children. After exclusions, 1147 exposures are reported here. No deaths were reported and only 37 children were admitted to hospital. The majority were considered to have either minimal or no features (925, 80.6%). Symptoms for 38 children were unknown. Symptoms reported in the other 184 children included nausea or vomiting (58), eye irritation, pain or conjunctivitis (29), skin irritation (28), abdominal pain (24), mouth or throat irritation (18) and diarrhoea (15). Where age was recorded, 60.5% (680) of children involved in suspected pesticide exposures were aged 2 years or less. The most common scenario for acute accidental exposure to pesticide in children was exposure after application (329, 28.7%) or due to poor storage (228, 19.9%).

CONCLUSIONS

Areas of potential concern identified included storage, access of young children to "laid" baits and pesticides, and exposures as a result of medication errors, with liquid head lice preparations being confused with other medicines. Use of NPIS systems provides a potentially useful method of toxicovigilance.

Adverse reactions associated with acetylcysteine

INTRODUCTION

Paracetamol (acetaminophen) is one of the most common agents deliberately ingested in self-poisoning episodes and a leading cause of acute liver failure in the western world. Acetylcysteine is widely acknowledged as the antidote of choice for paracetamol poisoning, but its use is not without risk. Adverse reactions, often leading to treatment delay, are frequently associated with both intravenous and oral acetylcysteine and are a common source of concern among treating physicians.

METHODS

A systematic literature review investigating the incidence, clinical features, and mechanisms of adverse effects associated with acetylcysteine.

RESULTS

A variety of adverse reactions to acetylcysteine have been described ranging from nausea to death, most of the latter due to incorrect dosing. The pattern of reactions differs with oral and intravenous dosing, but reported frequency is at least as high with oral as intravenous. The reactions to the intravenous preparation result in similar clinical features to true anaphylaxis, including rash, pruritus, angioedema, bronchospasm, and rarely hypotension, but are caused by nonimmunological mechanisms. The precise nature of this reaction remains unclear. Histamine now seems to be an important mediator of the response, and there is evidence of variability in patient susceptibility, with females, and those with a history of asthma or atopy are particularly susceptible. Quantity of paracetamol ingestion, measured through serum paracetamol concentration, is also important as higher paracetamol concentrations protect patients against anaphylactoid effects. Most anaphylactoid reactions occur at the start of acetylcysteine treatment when concentrations are highest. Acetylcysteine also affects clotting factor activity, and this affects the interpretation of minor disturbances in the International Normalized Ratio in the context of paracetamol overdose.

CONCLUSION

This review discusses the incidence, clinical features, underlying pathophysiological mechanisms, and treatment of adverse reactions to acetylcysteine and identifies particular "at-risk" patient groups. Given the commonality of adverse reactions associated with acetylcysteine, it is important to ensure that any adverse event does not preclude patients from receiving maximal hepatic protection, particularly in the context of significant paracetamol ingestion. Further work on mechanisms should allow specific therapies to be developed.

Hemodynamic effects of methadone and dihydrocodeine in overdose

BACKGROUND

Opioid overdose is an increasing health problem worldwide. The cardiovascular toxicity of opioids contributes to morbidity and mortality in overdose but the hemodynamic effects of opioids reported in animal and human studies are contradictory.

METHODS

We performed a prospective observational study of patients admitted to hospital following an overdose of methadone, dihydrocodeine, or low dose paracetamol (10 each). Basic cardiovascular indices including peripheral blood pressure, pulse rate, radial augmentation index and derived measures of aortic systolic, diastolic, pulse, and mean and end systolic pressures were measured every six hours for up to 18-23 hours after exposure or until hospital discharge.

RESULTS

Dihydrocodeine and methadone significantly reduced peripheral and aortic systolic, mean and end systolic pressures. Both opioids significantly decreased peripheral pulse pressure, but only methadone decreased aortic blood pressure. Dihydrocodeine reduced systemic and aortic diastolic blood pressure, an effect not induced by methadone. Methadone significantly reduced peripheral pulse pressure. Augmentation index and heart rate, however, did not change. Both opioids decreased arterial oxygen saturation.

CONCLUSION

These results suggest that dihydrocodeine and methadone in overdose both have a significant effect on central and peripheral hemodynamics. These effects might be expected to reduce cardiac afterload, providing a pharmacological explanation for the apparent benefit of opioids in cardiovascular diseases.

Variability in the quality of overdose advice in Summary of Product Characteristics (SPC) documents: gut decontamination recommendations for CNS drugs

AIMS

Deliberate self-poisoning is a major cause of morbidity and mortality. The Summary of Product Characteristics (SPC) document is a legal requirement for all drugs, and Section 4.9 addresses the features of toxicity and clinical advice on management of overdose. The quality and appropriateness of this advice have received comparatively little attention.

METHODS

Section 4.9 of the SPC was examined for all drugs in the central nervous system (CNS) category of the British National Formulary. Advice concerning gut decontamination was examined with respect to specific interventions: induced vomiting, oral activated charcoal, gastric lavage, and other interventions. Data were compared with standard reference sources for clinical management advice in poisoning. These were graded 'A' if no important differences existed, 'B' if differences were noted but not thought clinically important, and 'C' if differences were thought to be clinically significant.

RESULTS

SPC documents were examined for 258 medications from 67 manufacturers. The overall agreement was 'A' in 23 (8.9%), 'B' in 28 (10.9%) and 'C' in 207 (80.2%). Discrepancies were due to inappropriate recommendation of induced emesis in 21.7% (95% confidence interval 17.1, 27.1), gastric lavage in 38.4% (32.7, 44.4), other gut decontamination in 5.8% (3.6, 9.4) and failure to recommend oral activated charcoal in 57.4% (51.1, 63.4).

CONCLUSIONS

Gut decontamination advice in SPC documents with respect to CNS drugs was inadequate. Possible reasons for the observed discrepancies and ways of improving the consistency of advice are proposed.

Alerting and Surveillance Using Poisons Information Systems (ASPIS): Outcomes from an international working group

BACKGROUND

In recent years, awareness of the risks of chemical and poison exposure has increased, and a number of highly publicized terrorist events have heightened community fears. In particular, there is concern surrounding the potential risk of a covert release, which underpins the need to develop robust methods of population surveillance.

AIMS AND METHODS

This article outlines the proceedings of a working group and focuses on the need for greater international cooperation and understanding of existing toxicological surveillance systems in a variety of countries. Poison control centers have well-established local networks and experienced staff, which make them well-placed to detect chemical and poison release. This needs further development to ensure timely detection of signals, which might be better achieved by robust international networks and consistent use of data collection tools. We illustrate some of the strengths and weaknesses of existing surveillance methods, and present a position statement on the minimum dataset required by future surveillance systems.

CONCLUSIONS

Poison control centers provide a useful platform for developing surveillance activity. Having proposed a number of common aims and objectives, it is hoped that these consensus statements will inform decision makers and stimulate discussion of how international toxicological surveillance programs might best be developed.

EJCP and clinical toxicology: the first 40 years

INTRODUCTION

The European Journal of Clinical Pharmacology is now 40 years old and its history and development parallel developments in the related discipline of clinical (medical) toxicology. The journal has published many papers over its history that have informed its readers of scientific advances that link clinical pharmacology and clinical toxicology.

DISCUSSION

This review will provide an overview of the developments in treatment of poisoning and how effects of poisoning may provide information for drug regulation and suggests ways in which developments in pharmacogenetics and metabolomics may stimulate future research in this area.

Effect of acute paracetamol overdose on changes in serum and urine electrolytes

AIMS

To investigate the effects of acute paracetamol overdose on renal function, serum and urine electrolyte excretion in man.

METHODS

Two studies were performed in patients admitted with paracetamol overdose: a retrospective study examining changes in serum electrolytes, and a prospective study evaluating changes in serum and urine electrolytes. A control group with SSRI overdose was included in the prospective study.

RESULTS

There was a significant dose-dependent relationship between admission (4 h) paracetamol concentration and fall in serum potassium in the retrospective study (P < 0.01) and a significant positive relationship between serum paracetamol at 4 h and fractional excretion of potassium at 12 h postingestion (P < 0.01) in the prospective study. No changes were seen in the control group. No cases developed renal failure.

CONCLUSIONS

Paracetamol overdose is associated with dose-related hypokalaemia, and kaliuresis of short duration (<24 h), suggesting a specific renal effect of paracetamol in overdose perhaps via cyclo-oxygenase inhibition. This effect seems distinct from any nephrotoxic effect of paracetamol.

Pattern of lithium exposure predicts poisoning severity: evaluation of referrals to a regional poisons unit

BACKGROUND

Lithium toxicity may result in severe clinical features. There is on-going uncertainty about the significance of serum lithium concentrations in patients with lithium toxicity.

AIM

To examine potential relationships between stated quantity of lithium ingested, serum lithium concentrations, and poisoning severity among patients referred to a regional poisons centre.

METHODS

Prospective evaluation of enquiries to the Scottish Poisons Information Bureau about lithium toxicity between 2000-2005 inclusive.

RESULTS

There were 172 enquiries, relating to acute ingestion (n = 101), acute-on-therapeutic ingestion (n = 38), or chronic poisoning (n = 33). Poisoning severity was moderate or severe in 9.9%, 26.3% (p < 0.05 vs. acute) and 54.5% (p < 0.005 vs. acute) of each group, respectively. Median (IQR) serum lithium concentrations in each group were: 2.4 (1.7-3.3) mmol/l, 2.1 (1.4-3.8) mmol/l, and 2.3 (1.9-3.3) mmol/l, respectively. The median stated quantities ingested in acute and acute-on-therapeutic lithium exposure were 5000 mg (2000-11 050 mg) and 4000 mg (2400-8820 mg), respectively.

DISCUSSION

Patients with acute-on-therapeutic and chronic poisoning are at greatest risk of severe toxicity. These differences cannot be explained by either the quantity of lithium ingested or serum lithium concentration alone.

Legislation restricting paracetamol sales and patterns of self-harm and death from paracetamol-containing preparations in Scotland

AIMS

To describe how changes in legislation to restrict paracetamol sales have affected overdose discharges and death associated with the drug in Scotland.

METHODS

A descriptive analysis of routine death and hospital discharge data for the entire Scottish population between 1995 and 2004. Patients in Scotland participated who were discharged from hospital with a diagnosis of poisoning; deaths in Scotland from diagnosis of poisoning 1995-2003 were also analysed. Outcome measures were changes in mortality and overdose due to poisoning involving paracetamol. A comparison was made of in-hospital and out-of-hospital mortality in fatalities involving paracetamol.

RESULTS

The majority of paracetamol-associated deaths were due to co-proxamol. Deaths associated with paracetamol alone or with ethanol occurred principally in hospital and were a minority of deaths overall. The proportion of in-hospital deaths attributed to paracetamol increased (post/pre ratio 1.347; 95% confidence interval 1.076, 1.639; P = 0.013). Overall numbers of cases discharged with poisoning fell. The proportion of these involving paracetamol in any form increased significantly in all groups except young men aged 10 to <20 years.

CONCLUSIONS

Legislation has not reduced mortality or proportional use of paracetamol in overdose, both of which appear to have increased in Scotland since pack-size limitations. Other approaches are necessary to reduce the death rate from overdoses involving paracetamol.

Five years of poisons information on the internet: the UK experience of TOXBASE

INTRODUCTION

In 1999, the UK adopted a policy of using TOXBASE, an internet service available free to registered National Health Service (NHS) departments and professionals, as the first point of information on poisoning. This was the first use worldwide of the internet for provision of clinical advice at a national level. We report the impact on database usage and NPIS telephone call loads.

METHODS

Trends in the pattern of TOXBASE usage from 2000-2004 are reported by user category. Information on the monographs accessed most frequently was also extracted from the webserver and sorted by user category. The numbers of telephone calls to the National Poisons Information Service (NPIS) were extracted from NPIS annual reports.

RESULTS

Numbers of database logons increased 3.5 fold from 102,352 in 2000 to 368,079 in 2004, with a total of 789,295 accesses to product monographs in 2004. Registered users increased almost tenfold, with approximately half accessing the database at least once a year. Telephone calls to the NPIS dropped by over half. Total contacts with NPIS (web and telephone) increased 50%. Major users in 2004 were hospital emergency departments (60.5% of logons) and NHS public access helplines (NHS Direct and NHS24) (29.4%). Different user groups access different parts of the database. Emergency departments access printable fact sheets for about 10% of monographs they access.

CONCLUSION

Provision of poisons information by the internet has been successful in reducing NPIS call loads. Provision of basic poisons information by this method appears to be acceptable to different professional groups, and to be effective in reducing telephone call loads and increasing service cost effectiveness.

Hospital admissions and deaths relating to deliberate self-harm and accidents within 5 years of a cancer diagnosis: a national study in Scotland, UK

The risk of suicide in cancer patients has been reported as elevated in several countries. These patients are exposed to many medicines that may confuse or provide a means for harm, potentially also increasing their risk from accidents. Ratios of observed/expected numbers of hospital admission and death events relating to deliberate self-harm (DSH) and accidents were calculated in the 5 years from a cancer diagnosis in Scotland 1981–1995, compared to the matched general population. The relative risk (RR) of suicide was 1.51 (95% confidence interval (CI): 1.29–1.76). The RR of hospital admissions for DSH was not significantly increased, suggesting a strong suicidal intent in DSH acts in cancer patients. Accidental poisonings and all other accidents were both increased (RR death=3.69, 95% CI: 2.10–6.00; and 1.58, 95% CI: 1.48–1.69, respectively) (RR hospital admissions=1.32, 95% CI: 1.19–1.47; and 1.55, 95% CI: 1.53–1.57, respectively). The association of only certain tumour types (e.g. respiratory) with suicide and accidental poisoning, and a broad range of tumour types with an elevated risk of all other accidents, suggests accidental poisoning categories may be a common destination for code shifting of some DSH events. A previous history of DSH or accidents, significantly increased the RR of suicide or fatal accidents, respectively (RR suicide=14.86 (95% CI: 4.69–34.97) vs 1.16 (95% CI: 0.84–1.55)) (RR accidental death=3.37 (95% CI: 2.53–4.41) vs 1.29 (95% CI: 1.12–1.49)). Within 5 years of a cancer diagnosis, Scottish patients are at increased RR of suicide and fatal accidents, and increased RR of hospital admissions for accidents. Some of these accidents, particularly accidental poisonings, may contain hidden deliberate acts. Previous DSH or accidents are potential markers for those most at risk, in whom to target interventional techniques.

Liver unit admission following paracetamol overdose with concentrations below current UK treatment thresholds

BACKGROUND

It has been suggested that current UK thresholds for treating paracetamol overdose should be reduced, following case reports of patients developing fatal liver failure after presenting with paracetamol concentrations below these thresholds.

AIM

To determine the frequency of severe liver dysfunction following paracetamol overdose when paracetamol concentrations are below current UK antidote thresholds.

DESIGN

Retrospective case note review.

METHODS

Details were collected from all patients admitted to liver transplant units in Newcastle and Edinburgh with paracetamol-induced hepatotoxicity.

RESULTS

Of 696 patients admitted to the two liver units following paracetamol overdose, 14 presented between 4 and 15 h after overdose with paracetamol concentrations below current UK treatment thresholds (estimated annual population rate 0.15/million person-years). Over the period of study, >100 000 presentations with paracetamol overdose would be expected in the catchment populations for these liver units.

DISCUSSION

In view of the rarity of this event, this research does not suggest a need to lower the current thresholds for antidotal treatment.

IMPACT OF LEGISLATIVE CHANGES ON PATTERNS OF ANTIPSYCHOTIC PRESCRIBING AND SELF-POISONING IN SCOTLAND: 2000-06

Recently, national guidelines have advocated greater use of atypical rather than typical antipsychotics in the treatment of schizophrenia. In addition, there have been safety concerns regarding the potential cardiotoxicity of certain antipsychotics taken in overdose. This has led regulatory authorities in the United Kingdom to restrict the use of thioridazine. The overall impact of these legislative changes on patterns of antipsychotic prescribing has received comparatively little attention. Therefore, we sought to examine the effects on community prescribing practices, and to determine whether this was accompanied by changes in patterns of antipsychotic poisoning. Between 2000-03, there was a rapid decline in the use of typical antipsychotics, whereas the use of atypical antipsychotics increased. The prevalence of atypical and typical antipsychotic prescribing has been approximately equal between 2003-06. During the same study period, hospital admissions due to typical antipsychotic poisoning also declined, however, the effects lagged behind changes in prescribing practice by 2-3 years. These data indicate that legislative changes that restrict the use of thioridazine and other typical antipsychotics are associated with a measurable reduction in the number of hospital admissions due to overdose with these agents.

How has legislation restricting paracetamol pack size affected patterns of deprivation related inequalities in self-harm in Scotland?

OBJECTIVE

To describe how changes in legislation to control sales and thus restrict the general availability of paracetamol have affected deprivation-related inequalities in deliberate self-harm associated with the drug in Scotland.

DESIGN AND SETTING

A descriptive analysis of routine death and hospital discharge data for the entire Scottish population between 1995 and 2002.

PARTICIPANTS

Patients in Scotland admitted to hospital with a diagnosis of poisoning and deaths in Scotland due to poisoning 1995-2002.

OUTCOME MEASURES

Changes in mortality and overdose rates by deprivation quintile, and case fatality rates due to poisoning involving paracetamol.

RESULTS

Rates of overdose involving paracetamol, while much higher in disadvantaged quintiles, fell in each deprivation quintile following the 1998 legislation. They then returned to levels similar, or above those in the mid 1990s. All quintiles were affected to a similar extent with the relationship between them remaining constant over time. Case fatality rates were significantly higher in more disadvantaged quintiles.

CONCLUSIONS

Marked inequalities exist in paracetamol related harm in Scotland. The most disadvantaged groups (both male and female) have higher overdose and death rates, as well as higher case fatality rates. Following the restrictions all social groups saw similar reductions in paracetamol related harm. This effect has been short-lived and rates have returned to pre-legislation levels. Legislation has not permanently affected overall use of paracetamol in overdose in Scotland or reduced the proportion of patients taking paracetamol as a component of the overdose in the longer term. An important public health policy has failed to achieve its objective and it is not clear why. We need a better understanding of why this measure had only short-term benefits if its full potential is to be achieved.

Redefining the ACE-inhibitor dose-response relationship: substantial blood pressure lowering after massive doses

OBJECTIVES

The blood pressure-lowering dose-response relationship for angiotensin converting enzyme (ACE) inhibitors is assumed to flatten at doses higher than those conventionally used in clinical practice. However, existing clinical trial data do not adequately address the haemodynamic effects of high ACE inhibitor dosages. Therefore, we examined the blood pressure responses in patients presenting to hospital following a deliberate ACE inhibitor overdose.

METHODS

The study design was a retrospective case review, and included all patients who presented to our hospital in the past 5 years after an ACE inhibitor overdose. The data collected were heart rate and systemic blood pressure at various times after ingestion and maximum haemodynamic derangement; these were compared to baseline or recovered values.

RESULTS

Data from 33 patients (24 men) were evaluated. The median (inter-quartile range, IQR) age of the patients was 49 years (IQR: 42-56 years). The median stated dose ingested was 140 mg (IQR: 60-280 mg), which is 20x (IQR: 7-42) the defined daily dose. The maximum fall in systolic blood pressure was 50 mmHg (IQR: 40-64 mmHg), diastolic blood pressure was 35 mmHg (IQR: 26-43 mmHg) and mean blood pressure was 39 mmHg (IQR: 30-47 mmHg).

CONCLUSIONS

The observed reduction in blood pressure following an overdose of an ACE inhibitor was greater than anticipated based on data from therapeutic doses. We conclude that a blood pressure-lowering dose-response relationship extends to higher ACE inhibitor doses than those conventionally used in clinical practice.

Co-proxamol overdose is associated with a 10-fold excess mortality compared with other paracetamol combination analgesics

AIMS

To assess the relative toxicity of co-proxamol in overdose in comparison to the 2 other paracetamol-opioid combination products, co-codamol and co-dydramol.

METHODS

Data collected over a 2-year period (July 2000-June 2002) was used to estimate the frequency of overdose and death for the three most popular paracetamol-opioid compound analgesics. Prescription data for Scotland and Edinburgh, the number of overdoses (derived from overdose admissions in Edinburgh) or Poisons Information Service contacts in Scotland, and national death records were used to calculate a series of indicators relating morbidity (admissions), surrogates of morbidity (poisons enquiries by telephone or internet) and mortality to prescriptions.

RESULTS

When related to prescription volume overdoses involving co-proxamol in Scotland were 10 times more likely to be fatal (24.6 (19.7, 30.4)) when compared with co-codamol (2.0 (0.88, 4.0)) or co-dydramol (2.4 (0.5, 7.2)). In contrast there was no difference in the presentation rate or enquiry rates for these analgesics when corrected for prescriptions.

CONCLUSIONS

The excess hazard from co-proxamol is due to inherent toxicity rather than increased use in overdose. We estimate from this study that withdrawal of co-proxamol would prevent 39 excess deaths per annum in Scotland alone.

Clinical toxicology: clinical science to public health

1. The aims of the present paper are to: (i) review progress in clinical toxicology over the past 40 years and to place it in the context of modern health care by describing its development; and (ii) illustrate the use of clinical toxicology data from Scotland, in particular, as a tool for informing clinical care and public health policy with respect to drugs. 2. A historical literature review was conducted with amalgamation and comparison of a series of published and unpublished clinical toxicology datasets from NPIS Edinburgh and other sources. 3. Clinical databases within poisons treatment centres offer an important method of collecting data on the clinical effects of drugs in overdose. These data can be used to increase knowledge on drug toxicity mechanisms that inform licensing decisions, contribute to evidence-based care and clinical management. Combination of this material with national morbidity datasets provides another valuable approach that can inform public health prevention strategies. 4. In conclusion, clinical toxicology datasets offer clinical pharmacologists a new study area. Clinical toxicology treatment units and poisons information services offer an important health resource.

ECG abnormalities in co-proxamol (paracetamol/dextropropoxyphene) poisoning

OBJECTIVES

1) To investigate ECG changes following co-proxamol (paracetamol 325 mg and dextropropoxyphene 32.5 mg) overdose in comparison to co-codamol (paracetamol and codeine) or co-dydramol (paracetamol and dihydrocodeine) in a prospective study. 2) To examine the relationship between estimated dextropropoxyphene dose and ECG changes in a larger patient population.

BACKGROUND

Co-proxamol is a common cause of drug-induced death and hospital admission in the United Kingdom. ECG changes following dextropropoxyphene have been reported in animals and man, including QRS prolongation.

METHODS

The prospective study was conducted on 15 patients and controls with overdose. A retrospective study of a cohort of 159 co-proxamol overdoses from a combined data set from Edinburgh and Newcastle, Australia was also conducted. The measured or estimated "four hour" plasma paracetamol level was used as a surrogate of the amount of dextropropoxyphene ingested.

RESULTS

In the prospective study co-proxamol overdose caused statistically significant QRS prolongation (mean [95% CI] 99.36 [96.19, 102.53] msec), compared to the other combination opioid-paracetamol products (82.84 [80.81, 84.88] msec) but no effect on PR or QTc. QRS duration increase was evident soon after exposure and remained prolonged and stable over the following 24 h. In the retrospective cohort study a dose dependency of effect on QRS was documented, although the correlation coefficient relating paracetamol level to effect was relatively weak (r = 0.338, Sig. [2-tailed] 0.003, n = 74).

CONCLUSIONS

QRS is significantly prolonged in co-proxamol overdose, and this prolongation is dose dependent. These findings have clinical relevance to the management of patients with co-proxamol poisoning.

A case control study to examine the pharmacological factors underlying ventricular septal defects in the North of England

BACKGROUND

Amphetamine exposure is associated with congenital cardiac abnormalities in animals. We previously reported an association between recreational use of 2,4-methylenedioxymethamphetamine (ecstasy, MDMA) and ventricular septal defect in babies born to users. We have carried out a case control study to investigate risks in the occurrence of ventricular septal defect in a cohort of babies born in the North East of England.

METHODS

Cases were identified from paediatric cardiology units in Newcastle upon Tyne and Leeds, and controls were recruited from the mothers of babies born in the same hospital as the index case. Research nurses carried out interviews using a structured questionnaire.

RESULTS

A total of 296 case control pairs were studied. There was insufficient exposure to ecstasy to test the primary hypothesis. Increased risk of ventricular septal defect was found to be associated with consumption of cough and cold remedies [pre-conception OR 2.2, 95% CI 1.41, 3.51; pregnancy OR 5.1, 95% CI 2.56, 11.27; exposure in either OR 2.83, 95% CI 1.85, 4.45; P<0.005] and in the case of non-steroidals for exposures in pregnancy (OR 4.2, 95% CI 1.54, 14.26; P<0.005).

CONCLUSIONS

These findings suggest that ventricular septal defect is associated with consuming the medications identified. They are also compatible with the hypothesis that sympathomimetics (pseudoephedrine, phenylephrine and phenylpropanolamine) present in cough mixtures cause the increased risk, and with our original hypothesis that sympathomimetics and amphetamines are potentially cardiotoxic in utero.

Electrocardiogram and cardiovascular changes in thioridazine and chlorpromazine poisoning

OBJECTIVES

To examine the effects of anti-psychotic medications on cardiovascular parameters in overdose. Specifically, to examine dose-response relationships for thioridazine and chlorpromazine.

METHODS

A retrospective study of case records of patients presenting to the Edinburgh poisons treatment unit over 3 years (2000-2002). Information--including that on stated dose ingested, ECG parameters, and pulse and blood pressure--was extracted from case notes.

RESULTS

A total of 224 chlorpromazine, 96 thioridazine and 99 patients ingesting other anti-psychotics were evaluated. Full data on all aspects, both dose and cardiovascular change, was available in 96 chlorpromazine, 36 thioridazine and 27 of the other anti-psychotic cases. For thioridazine, there was a significant dose-response relationship for increasing heart rate and increasing QTc but not other cardiovascular changes. For chlorpromazine, there was no dose-response relationship for ECG changes, but there was a significant dose-response relationship for increasing heart rate and reduction in mean blood pressure.

CONCLUSIONS

We have confirmed a relationship between increasing dose of thioridazine and prolongation of QTc in overdose patients. No such change was observed with chlorpromazine. Both of these agents are reported to cause QT prolongation, but this study suggests that the nature of these effects is different for each agent. Poisoned patients may offer ways of exploring in more detail, and at a larger dose range, the effects of potentially cardiotoxic drugs in humans.

Are selective serotonin re-uptake inhibitors associated with an increased risk of self-harm by antidepressant overdose?

OBJECTIVE

To investigate likelihood of self-harm by overdose with antidepressant drugs of different types by examining hospital admission data and poisons inquiries and relating them to prescribing.

DESIGN

Retrospective analysis of prospectively collected data on overdose admissions, poisons inquiries and prescribing of antidepressants in Edinburgh and Scotland.

SETTING

Poisons treatment unit of the Royal Infirmary of Edinburgh and its surrounding catchment for overdose cases and Scotland for poisons inquiries.

PARTICIPANTS

All patients admitted to the Royal Infirmary of Edinburgh between 1 January 2000 and 31 December 2002 with an overdose involving an antidepressant.

MAIN OUTCOME MEASURES

Overdose admissions (patients) in relation to prescribing in Edinburgh and poisons inquiries in relation to prescription rates in Scotland.

RESULTS

There were 1656 admissions involving 1343 patients. The likelihood of admission for an individual patient in relation to volume of prescribing (likelihood ratio: 95%CI) in the catchment was somewhat smaller for amitriptyline (0.83:0.74-0.92) and sertraline (0.79:0.63-0.99), and somewhat greater for mirtazapine (1.99:1.57-2.51), trazadone (1.30:1.09-1.54) and venlafaxine (0.97:1.81-1.16) [corrected] For poisons inquiries in Scotland, the excess for venlafaxine and mirtazapine was confirmed and likelihood of an inquiry lowest for selective serotonin re-uptake inhibitors (SSRIs).

CONCLUSIONS

There was no evidence of an excess likelihood of presentation with overdose with SSRIs, and the likelihood was reduced with sertraline. There was a small excess of both admissions and poisons inquiries for mirtazapine and venlafaxine. This is a concern in view of the increased toxicity of venlafaxine in overdose in comparison with SSRIs.

Comparative Toxicity of Citalopram and the Newer Antidepressants After Overdose

OBJECTIVE

To compare the toxicity of citalopram, venlafaxine, mirtazapine, and nefazadone after overdose.

METHODS

Two-year retrospective review of consecutive patients admitted to the toxicology unit of Edinburgh Royal Infirmary. Outcome measure included physiological variables, ECG recordings, peak creatine kinase, development of arrhythmias, seizure, tremor or agitation, and the need for admission to a critical care facility.

RESULTS

A total of 225 patients were studied. Venlafaxine was associated with a significantly higher pulse rate (p < 0.0001) and tremor (p = 0.007) than other antidepressants. Citalopram was associated with a significantly longer QT interval on ECG recording (p < 0.0001) but mean QTc durations were not significantly different between all drugs studied. No arrhythmias were recorded. Only venlafaxine and citalopram caused seizures and were associated with the need for admission to Intensive Care, but there was no significant difference between them.

CONCLUSIONS

Mirtazapine and nefazadone appear safe in overdose and were associated with minimal features of neurological or cardiovascular toxicity. Citalopram is more likely to cause QT prolongation but other features of cardiovascular toxicity were uncommon. Both citalopram and venlafaxine are proconvulsants. Venlafaxine also causes more frequent features of the serotonin syndrome.

The epidemiology of self-poisoning in the UK

Self-poisoning by ingestion or inhalation is common, and it is important to study its various epidemiological manifestations with clear definitions. Data on fatal self-poisonings are recorded nationally within the UK and are codified according to the International Classification of Diseases (ICD) revision relevant at the time. Most fatal self-poisonings are codified as suicides, accidental deaths or undetermined deaths ('open verdicts'). Non-fatal self-poisoning data, whether accidental or as a manifestation of deliberate self-harm, are recorded through hospital discharge information nationally but are not routinely published in the same way as mortality data. The bulk of the UK's published epidemiological information on nonfatal self-poisoning episodes is largely based on individual hospitals' admission or discharge records ('special studies'). After establishing definitions for different self-poisoning categories we discuss the published data on self-poisoning as they relate to suicide, accidental self-poisoning and deliberate self-harm in the UK.

Quinine intoxications reported to the Scottish Poisons Information Bureau 1997-2002: a continuing problem

Quinine is widely prescribed in the UK for night cramps. Its potential toxicity in overdose is well known. We have reviewed the Scottish experience of enquiries regarding quinine overdose to the poisons information service responsible for Scotland over a 6-year period. Between 1997 and 2002 there were 96 reports of suspected quinine toxicity from Scotland (population 5.2 million), 19 of which were in children. The largest quantities of drug ingested were in patients between the ages of 11 and 30. In comparison with older studies the pattern of quinine poisoning does not appear to have changed in the UK over 20 years, despite recognition that it is a toxic agent in overdose, and particularly in children.

Mortality study of 18 000 patients treated with omeprazole

BACKGROUND

The long term safety of potent gastric acid suppressive therapy has yet to be established.

METHOD

General practice record review at a median interval of 26 months followed by retrieval of details of all deaths within four years using the UK National Health Service Central Registers in 17 936 patients prescribed omeprazole in 1993-1995. Death rates were compared with general population rates.

RESULTS

Records of 17 489 patients (97.5%) were examined. A total of 12 703 patients received further scripts for antisecretory drugs, 8097 for omeprazole only (65.6%): 3097 patients have died. All cause mortality was higher in the first year (observed/expected (O/E) 1.44 (95% confidence intervals (CI) 1.34-1.55); p<0.0001) but had fallen to population expectation by the fourth year. There were significant mortality increases in the first year, falling to or below population expectation by the fourth year, for deaths ascribed to neoplasms (1.82 (95% CI 1.58-2.08); p<0.0001), circulatory diseases (1.27 (95% CI 1.13-1.43); p<0.0001), and respiratory diseases (1.37 (95% CI 1.12-1.64); p<0.001). Increased mortality ascribed to digestive diseases (2.56 (95% CI 1.87-3.43); p<0.0001) persisted, although reduced. Increased mortality rates for cancers of the stomach (4.06 (95% CI 2.60-6.04); p<0.0001), colon and rectum (1.40 (95% CI 0.84-2.18); p=0.075), and trachea, bronchus, and lung (1.64 (95% CI 1.19-2.19); p<0.01) seen in the first year had disappeared by the fourth year but that for cancer of the oesophagus had not (O/E 7.35 (95% CI 5.20-10.09) (p<0.0001) in year 1; 2.88 (95% CI 1.62-4.79) (p<0.001) in year 4). Forty of 78 patients dying of oesophageal cancer had the disease present at registration. Twenty seven of those remaining cases had clinical evidence of Barrett's disease, stricture, ulcer, or oesophagitis at registration (O/E 3.30 (95% CI 2.17-4.80)). Six deaths occurred in patients with hiatal hernia or reflux only (O/E 1.02 (95% CI 0.37-2.22)) and five in patients without oesophageal disease (O/E 0.77 (95% CI 0.25-1.80)). No relationships were detected with numbers of omeprazole scripts received.

CONCLUSIONS

Increases in mortality associated with treatment are due to pre- existing illness, including pre-existing severe oesophageal disease. There was no evidence of an increased risk of oesophageal adenocarcinoma in those without oesophageal mucosal damage recorded at registration.

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.

Changes in paracetamol, antidepressants and opioid poisoning in Scotland during the 1990s

BACKGROUND

Overdose is one of the commonest causes of medical admissions to UK hospitals. In Scotland (pop. 5.1 million), all NHS hospital discharge data is uniquely linked to enable identification of individuals re-presenting with the same diagnosis.

AIM

To examine trends in discharges for poisoning, in particular paracetamol, antidepressants and opioids from 1990-99.

DESIGN

Retrospective analysis.

METHODS

Discharge data from the Scottish Morbidity Record (SMR01) and mortality data from the General Register Office for Scotland (GROS) were analysed for 1990-99 by age and gender for the relevant codes.

RESULTS

Overall discharge rates increased until 1997, after which they fell. This pattern was seen in paracetamol-related discharges, but not for antidepressants or for opioids. Overdose was more common in females, except for opioids. Discharges related to opioids increased in an exponential manner over the decade, five-fold in women and six-fold in men in 10 years.

DISCUSSION

Increases in opioid-related presentations are of major concern. Changes in paracetamol pack-size have been associated with reduced discharge rates. In Scotland the age group with the highest rate of discharge (15-24 years) with paracetamol overdose is not the one with the highest mortality.

Adult respiratory distress syndrome and renal failure associated with citalopram overdose

A 45-year-old man ingested 3000 mg of citalopram hydrobromide (2400 mg citalopram). He presented to the Emergency Department 2 hours post-ingestion with a pulse of 100 beats/min and blood pressure of 120/80 mmHg. His electrocardiogram (ECG) was normal. Chest X-ray showed bilateral shadowing, with no evidence of aspiration of gastric contents. Shortly after, he had three tonic-clonic seizures, requiring intravenous diazepam. Eight hours post-ingestion he became oliguric with deteriorating renal function, despite normal arterial and central venous pressures. He became increasingly hypoxic, with chest X-ray changes compatible with adult respiratory distress syndrome (ARDS). Despite treatment with 100% oxygen and continuous positive airway pressure, his gas exchange continued to deteriorate, requiring intubation and ventilation. His renal function also deteriorated with a peak creatinine of 492 micromol/L on day 4 in the absence of rhabdomyolysis. There was complete spontaneous recovery of renal function after 2 weeks. A peak plasma total citalopram (R+S enantiomers) concentration of 1.92 mg/L was recorded 2 hours post-ingestion. Total norcitalopram concentrations continued to rise up to 24 hours post-ingestion. Citalopram has been associated with seizures, ECG abnormalities, rhabdomyolysis and coma after overdose. The renal and respiratory complications seen in this patient have not been reported previously.

Paracetamol toxicity: epidemiology, prevention and costs to the health-care system

Paracetamol has been used as an analgesic and antipyretic for many years, with toxicity first noted in the 1960s. Since then the incidence of poisoning has increased, and paracetamol is now the most common drug in self-poisoning, with a high rate of morbidity and mortality. The use, abuse and ways of reducing paracetamol toxicity are reviewed, but in view of the potential for harm, serious consideration should be given to changing the legal status of paracetamol, possibly to a prescription-only medicine.