We conducted research on the use of co-proxamol (a prescription-only drug which is a combination of dextropropoxyphene and paracetamol) in both suicide and deliberate self-poisoning. Our work highlighted the dangers of co-proxamol in overdose - death may result from relatively few tablets, and can occur very rapidly, before hospital treatment can be received. The effects on respiratory depression are enhanced by alcohol or other drugs which depress the central nervous system.
Our study of national mortality figures and local non-fatal self-poisonings showed that the risk of dying after co-proxamol overdose was 2.3 times that for tricyclic antidepressants and 28.1 times that for paracetamol. Fatal overdoses due to co-proxamol were the second most frequent means of suicide with prescribed drugs in England and Wales.
This work, and that of other researchers, contributed to the reappraisal of the role of co-proxamol by the Committee on Safety of Medicines. On 31st January 2005 the Medicines and Healthcare products Regulatory Agency (MHRA) announced the planned withdrawal of the drug.
As part of a National Institute for Health Research (NIHR) programme of research in support of the National Suicide Prevention Strategy for England we investigated the impact of the MHRA announcement of the withdrawal of co-proxamol on analgesic prescribing and poisoning mortality. A steep reduction in prescribing of co-proxamol following the announcement was accompanied by significant increases in prescribing of some other analgesics (cocodamol, paracetamol, codydramol, and codeine). This was associated with a major reduction in deaths involving co-proxamol in 2005-2007 compared with the expected number of deaths (an estimated 295 fewer suicides and an estimated 349 fewer deaths including accidental poisonings). There was no statistical evidence for an increase in deaths involving either other analgesics or other drugs. The study is published in the BMJ (see below).
Following the UK initiative prescribing of dextropropoxyphene ceased in all other countries in the European Union, and dextropropoxyphene products were withdrawn from the US and Canadian markets, and in Sweden, New Zealand and Zimbabwe.
Hawton, K., Bergen, H., Simkin, S., Wells, C., Kapur, N. & Gunnell, D. (2012). Six-year follow-up of impact of co-proxamol withdrawal in England and Wales on prescribing and deaths: time-series study. PLoS Medicine, 9(5): e1001213. doi:10.1371/journal.pmed.1001213
Hawton, K., Bergen, H., Waters, K., Murphy, E., Cooper, J. & Kapur, N. (2011). Impact of withdrawal of the analgesic co-proxamol in the UK on non-fatal self-poisoning. Crisis 32, 81-87. doi: 10.1027/0227-5910/a000063
Hawton, K., Bergen, H., Simkin, S., Brock, A., Griffiths, C., Romeri, E., Smith, K. L., Kapur, N., Gunnell, D. (2009) Effect of withdrawal of co-proxamol on prescribing and deaths from drug poisoning in England and Wales: time series analysis. BMJ 2009;338;b2270; doi:10.1136/bmj.b2270