During the six years following the withdrawal of the analgesic co-proxamol in the UK in 2005, there was a major reduction in poisoning deaths involving this drug, without apparent significant increase in deaths involving other analgesics. These are the findings of a study by Keith Hawton of the University of Oxford, UK and colleagues and published in this week's PLoS Medicine.
Co-proxamol, a prescription analgesic (or pain killer) containing paracetamol and the opioid dextropropoxyphene, was implicated in a fifth of drug-poisoning suicides in England and Wales between 1997 and 1999. Mainly in response to concerns over the drug's widespread use for suicidal poisoning, co-proxamol was withdrawn completely from use in the UK during the period 2005-2007. A previous study by the same authors showed beneficial effects on the number of co-proxamol-related suicides and no evidence of an increase in poisoning deaths from other prescription analgesics during this three-year withdrawal phase.
But what about the longer-term effects of co-proxamol withdrawal? In this interrupted time series study, Hawton and colleagues assessed the impact of coproxamol withdrawal in England and Wales by comparing data on analgesic prescribing and suicide rates collected between 1998 and 2004 and between 2005 and 2010. They found that on average, from 2008 to 2010 there were 20 co-proxamol-related deaths per year, including suicides and accidental poisonings, in comparison to more than 250 per year during the 1990s.
Although the authors did not investigate suicides related to the use of multiple drugs or investigate whether suicides involving methods other than drug-related poisoning have increased since co-proxamol withdrawal, they found little evidence of a change in the number of poisoning deaths involving other analgesics after co-proxamol withdrawal, in spite of increased prescribing. Despite its limitations, the study's findings suggest that the withdrawal of co-proxamol in the UK, and possibly elsewhere, should have major beneficial effects on suicide rates, at least in the relatively short term.
The authors comment: "Now that prescribing of the more toxic constituent of co-proxamol (dextropropoxyphene) has been withdrawn throughout Europe and production has ceased in the US and Canada the impact of this initiative should be evaluated on a larger scale."
More information: Hawton K, Bergen H, Simkin S, Wells C, Kapur N, et al. (2012) Six-Year Follow-Up of Impact of Co-proxamol Withdrawal in England and Wales on Prescribing and Deaths: Time-Series Study. PLoS Med 9(5): e1001213. doi:10.1371/journal.pmed.1001213
KH and SS were temporary advisors to the MHRA for its evaluation of the efficacy and safety profile of co-proxamol. CW works for the Office for National Statistics. All other authors have declared that no competing interests exist.
The authors acknowledge financial support from the National Institute for Health Research (NIHR) Programme Grants for Applied Research scheme as part of a NIHR programme of work related to suicide prevention (RP-PG-0606-1247).