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Keith Hawton a Centre for
Suicide Research, University Department of Psychiatry, Warneford
Hospital, Oxford OX3 7JX, b ICRF/NHS Centre for Statistics in Medicine, Institute of
Health Sciences, Oxford OX3 7LF, c School of Psychiatry and Behavioural
Sciences, Department of Psychiatry, University of Manchester,
Withington Hospital, Manchester M20 8LR, d Department of Social Medicine, University of Bristol,
Bristol BS8 2PR
Correspondence to: K Hawton keith.hawton{at}psych.ox.ac.uk
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Abstract |
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Objective:
To evaluate the effects on suicidal
behaviour of legislation limiting the size of packs of paracetamol and
salicylates sold over the counter.
Design:
Before and after study.
Setting:
UK population, with detailed monitoring
of data from five liver units and seven general hospitals, between September 1996 and September 1999.
Subjects:
People who died by suicidal or
accidental overdose with paracetamol or salicylates or who died of
undetermined causes; patients admitted to liver units with hepatic
paracetamol poisoning; patients presenting to general hospitals with
self poisoning after taking paracetamol or salicylates.
Main outcome measures:
Mortality from paracetamol
or salicylate overdose; numbers of patients referred to liver units or
listed for liver transplant; numbers of transplantations; numbers of
overdoses and tablets taken; blood concentrations of the drugs;
prothrombin times; sales to pharmacies and other outlets of paracetamol
and salicylates.
Results:
Numbers of tablets per pack of
paracetamol and salicylates decreased markedly in the year after the
change in legislation on 16 September 1998. The annual number of deaths from paracetamol poisoning decreased by 21% (95% confidence interval 5% to 34%) and the number from salicylates decreased by 48% (11% to
70%). Liver transplant rates after paracetamol poisoning decreased by
66% (55% to 74%). The rate of non-fatal self poisoning with paracetamol in any form decreased by 11% (5% to 16%), mainly because of a 15% (8% to 21%) reduction in overdoses of paracetamol in non-compound form. The average number of tablets taken in paracetamol overdoses decreased by 7% (0% to 12%), and the proportion involving >32 tablets decreased by 17% (4% to 28%). The average number of tablets taken in salicylate overdoses did not decrease, but 34% fewer
(2% to 56%) salicylate overdoses involved >32 tablets. After the
legislation mean blood concentrations of salicylates after overdose
decreased, as did prothrombin times; mean blood concentrations of
paracetamol did not change.
Conclusion:
Legislation restricting pack sizes of
paracetamol and salicylates in the United Kingdom has had substantial
beneficial effects on mortality and morbidity associated with self
poisoning using these drugs.
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What is already known on this topic
What this study adds
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Introduction |
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Deliberate self poisoning with non-opiate analgesics, especially paracetamol, is common in the United Kingdom, resulting in a substantial number of deaths each year.1-4 The increasing misuse of paracetamol has paralleled a rise in sales, and by implication greater availability, of the drug.5 In recent years self poisoning with paracetamol has also been a major cause of liver poisoning: the drug is responsible for approximately half of all cases of liver failure in the United Kingdom.6
On 16 September 1998 legislation was introduced in the United Kingdom limiting pack sizes of paracetamol, salicylates, and their compounds sold over the counter (box).7 At the same time nearly all preparations became available only in blister packs. The justification for the legislation was that analgesic self poisoning is often highly impulsive and associated with both low suicidal intent and limited knowledge of the possible consequences, 8 9 and that the number of cases of overdose might be reduced by limiting availability of the drugs. There is evidence that mortality from paracetamol self poisoning is lower in countries with smaller maximum pack sizes than in the United Kingdom.5
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Legislation on packaging of paracetamol and salicylates (16 September 1998)
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We conducted a prospective study to assess the impact of this
legislation on mortality from paracetamol and salicylate overdose; cases of liver poisoning after paracetamol overdose, as reflected in
numbers of liver transplantations, referrals to liver units, and
abnormal liver function tests; number and nature of cases of
paracetamol and salicylate overdose; and sales of paracetamol and salicylates.
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Methods |
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Mortality from overdoses of paracetamol and salicylates
The Office for National Statistics supplied data on drug related
deaths (suicides and accidental self poisoning) and deaths from
undetermined cause in England and Wales for September 1996 to September
1999. We included deaths from undetermined cause and accidental
poisonings because using suicide verdicts alone to assess overall
mortality from suicide is problematic.10 We extracted data
on deaths of people aged 12 years and over where paracetamol or
salicylates were recorded as the only drug involved. We also examined
data on deaths where paracetamol or salicylates were part of a compound
(excluding co-proxamol) or were taken with another, separate, drug.
Data for 1999 are provisional, as some cases are still under coroner's
review. The data from 1996 to 1998 indicated that records for 4.5% of
cases were likely to be missing.
Liver transplantation and referrals to liver transplant units
Data on numbers of admissions after paracetamol overdose, patients
listed for liver transplantation, and patients receiving transplants
were supplied by five liver units in England for October 1996 to
September 1999. In most of these units data were obtained from review
of routinely kept clinical records.
Non-fatal self poisoning with paracetamol and
salicylates
Data were collected in Oxford (one hospital), Bristol and Bath
(four hospitals), and Manchester (two hospitals) on all presentations
with self poisoning between 16 September 1997 and 15 September 1999. Figures for self poisoning with paracetamol, paracetamol compounds
(excluding co-proxamol), salicylates, salicylate compounds, and other
drugs were extracted. Information was not available for Manchester for
all salicylate overdoses. The number of tablets taken in each overdose
was recorded; where the number was imprecise we used standard
approximations (details available from authors).
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Sales data
Intercontinental Medical Statistics supplied data for September
1996 to September 1999 on monthly sales of paracetamol and salicylate
preparations to pharmacies and other outlets in the United Kingdom.
These data cover 97% of sales to pharmacies, including Boots (but
excluding its brand name products). Because manufacturers were given 12 months' notification of the legislation, and rapid changes in pack
sizes occurred during that period, sales in the 12 months after the new
legislation were compared with those in the penultimate 12 months
before legislation. We included only sales of packs of fewer than 100 tablets as we could not determine the proportion of large packs sold on prescription.
Statistical analyses
Rates of death, non-fatal self poisoning, admission to liver
units, listing for liver transplantation, and transplantation were
calculated separately for periods of 12 months before and after the new
legislation. Exact confidence intervals for these rates were computed
using the Poisson distribution. Relative incidence rates are ratios of
the rate after the new legislation to the rate before legislation and
are expressed as percentage increases or decreases. The data on
mortality for January to September 1999 are provisional, as data on
some cases still under coroner's review are missing. Similar data from
1996 to 1998 indicate that the number of cases with missing data in
this period is likely to be 4.5% of the figures available to us. An adjustment of 4.5% was therefore made to the number of deaths after
legislation. The proportions of deaths and non-fatal self poisonings
attributed to each drug (and to combinations of drugs) before and after
the legislation were compared as risk ratios, the changes being
expressed as percentage increases or decreases. Confidence intervals
and levels of statistical significance were computed using Poisson regression.
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Results |
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Mortality from paracetamol and salicylate overdoses in England
and Wales
After the introduction of the new law the proportion of all
relevant drug related deaths that were attributable to paracetamol or
salicylates on their own decreased significantly (table 1). Compared
with the annual rate in the two years before the change, in the next 12 months there were 40 fewer deaths from paracetamol poisoning and 15 fewer from salicylates (after adjustment for missing data). Annual
numbers of deaths in which paracetamol or salicylates were taken in
combination with other drugs (which may have caused the death) and of
deaths in which both paracetamol and salicylates were taken did not
change significantly.
Admissions to liver units and numbers of liver transplantations
in England
After the legislation the annual number of admissions with hepatic
paracetamol poisoning to liver units declined by 30% (95% confidence
interval 22% to 37%) compared with the two years before the
legislation (fig 1). Significant reductions occurred in all five
units (data for one centre have already been published).11
Across the five units the annual number of admissions decreased from
310 in the 24 months before the change to 193 in the 12 months
after.
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Non-fatal self poisoning with paracetamol and salicylates
Table 2 shows the number of presentations to seven general
hospitals in Bristol and Bath, Oxford, and Manchester after self
poisoning with paracetamol or salicylates in the 12 months before and
after the legislation. Although overdoses involving paracetamol of any
kind as a proportion of the total number of cases of self poisoning did
not change, the absolute number decreased significantly by 11% (5% to
16%). The proportion of cases in which paracetamol alone was used (the
most common type of paracetamol overdose) also decreased significantly
(data available for Oxford and Bristol and Bath only). The proportion
of overdoses involving paracetamol compounds increased significantly
only in Bristol and Bath. Numbers of overdoses involving salicylates,
whether alone or in compounds, did not change
significantly.
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Biochemical data and results of tests of liver function
The mean highest blood paracetamol concentrations recorded in
Oxford, Bristol and Bath, and Manchester did not change after the
legislation, but the mean highest prothrombin times decreased slightly
(-2% (0% to -4%)). The mean highest salicylate concentrations
recorded in Oxford and Bristol also decreased (-17% (-11% to
-21%)).
Sales data
The mean numbers of tablets per pack of paracetamol and
salicylates sold to pharmacies in the United Kingdom decreased markedly
in the 12 months after the legislation compared with the penultimate 12 months before. There was, however, a compensatory increase in the
number of packs sold of paracetamol, such that the total number of
tablets of paracetamol sold did not change (table 4). The total numbers
of tablets of paracetamol compounds, salicylates, and salicylate
compounds sold to pharmacies decreased significantly. The numbers of
tablets sold of preparations combining both paracetamol and salicylates
did not change significantly.
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Discussion |
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The legislation introduced in September 1998 to reduce the maximum number of tablets in packs of paracetamol and salicylates and to ensure the inclusion of stronger warnings of the danger of taking too many tablets was followed by significant reductions in mortality and morbidity resulting from self poisoning with these drugs. Although interpreting results from a study with a simple before and after design is problematic,12 the evidence for a causal relation between the legislation and the changes in mortality and morbidity is strong, especially because the decrease in the number of cases of self poisoning with paracetamol alone and in the resulting mortality came after several years of successively increasing numbers of paracetamol overdoses and related deaths. 1 2 13 The effects of the legislation on mortality, numbers of cases of self poisoning, morbidity, and drug sales were consistent for both paracetamol and salicylates.
Methodological issues
It is important to consider the possibility of incomplete or
inconsistently recorded data when interpreting the results of before
and after studies. We made an adjustment to account for the
incompleteness of mortality data for 1999. However, the degree of
undercounting was small and had been consistent over the three previous
years. Our investigation of trends in self poisoning was based on
routinely collected data from seven hospitals. Although clinicians in
these centres were aware of the introduction of the legislation, there
is no reason to believe that this would have affected their recording
of routine clinical information. Another potential limitation of before
and after studies is the difficulty of accounting for underlying trends in the outcomes; analysis based on proportional incidence counters this. We are not aware of any changes in policy on blood testing in
cases of overdose during the study period. One liver unit did not
provide data for inclusion in the analyses, but there is no reason to
expect that the pattern in this centre would have been any different
from that in the other centres.
Mortality and morbidity
The number of deaths from self poisoning with paracetamol alone
went down by 40 from the 12 months before the law change to the 12 months after, and the corresponding figure for salicylates was about
15. The reduction in mortality from paracetamol self poisoning was
reflected in reduced morbidity. The reduction in the number of
admissions to liver units because of paracetamol poisoning has already
been highlighted.11 Our analysis of data from five liver
units shows that there was an even greater reduction in the number of
these admissions that progressed to liver transplantation.
Non-fatal self poisoning
These trends were also reflected in a reduction in the number and
proportion of overdoses in which paracetamol was taken alone, the
predominant type of overdose involving paracetamol. The small but
significant increase in overdoses in which paracetamol compounds or
paracetamol together with other drugs were taken may be a result of the
decreased availability of paracetamol and consequent use of other drugs
to increase the size of the overdose. There was a small reduction in
the mean number of paracetamol tablets taken per overdose, and a
somewhat more marked decrease in the number of overdoses in which a
large number of tablets was taken. Also, although the maximum blood
concentrations of paracetamol in patients in whom measurements were
taken did not change overall, there was a small decrease in the
proportion of patients with abnormal prothrombin times
a sensitive
measure of liver poisoning.14
Sales of paracetamol and salicylates
Trends in the nature and number of paracetamol and salicylate
overdoses and their consequences are compatible with sales data, which
showed a marked reduction in the mean number of tablets per pack sold
to pharmacies and some other outlets for all relevant preparations in
the 12 months after the new legislation compared with the penultimate
12 months before. Although increases in the number of packs sold of
paracetamol and paracetamol-salicylate compounds seemed to compensate
for these decreases, the net effect would have been a reduction in the
maximum number of tablets in households. The sales data cover most but
not all relevant products and would reflect sales over the counter.
Conclusion
The legislation has been relatively successful, in that it was
followed by a marked reduction in the number of deaths resulting from
overdoses of paracetamol and salicylates and by fewer liver
transplantations and reduction in other indices of morbidity associated
with paracetamol self poisoning. The results indicate that the main
factor was the reduction in the number of tablets per pack. Elsewhere
we have shown that stronger warnings on labels are unlikely to have
much impact.8
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Acknowledgments |
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We thank Sue Kelly, Olivia Christophersen, and Alan Baker (Office for National Statistics); Claire Cuff (Intercontinental Medical Statistics); John McVittie (clinical biochemistry, John Radcliffe Hospital, Oxford); Sue Mulholland (Centre for Suicide Research, Oxford University); the staff of the department of psychological medicine, John Radcliffe Hospital; Paul Thomas and James Osborn (chemical pathology, Bristol Royal Infirmary); Ann Fisher (haematology, Wythenshawe Hospital, Manchester); Tony Cummings (biochemistry, Manchester Royal Infirmary); Julia Wendon (liver unit, King's College Hospital, London); Andrew Burroughs (liver unit, Royal Free Hospital, London); James Neuberger and Damian Dowling (liver unit, Queen Elizabeth Hospital, Birmingham); Mervyn Davies and Helen Aldersley (liver unit, St James's Hospital, Leeds); Oliver James, Martin Prince, and Mark Hudson (liver unit, Freeman Hospital, Newcastle).
Contributors: KH initiated the study and contributed to the design, interpretation, and reporting. ET coordinated the collection of the data and contributed to the study design, interpretation, and reporting. JD conducted the statistical analyses and contributed to the interpretation and reporting. LA and DG contributed to the design of the study, data collection, interpretation, and reporting. JC and OB contributed to database design, data collection, and reporting. KH is guarantor for the study.
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Footnotes |
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Funding: South East Region NHSE Research and Development. KH is also supported by Oxfordshire Mental Healthcare Trust.
Competing interests: None declared.
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References |
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(Accepted 8 February 2001)
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