They are the most powerful painkillers that family doctors have at their disposal, and as the queue of patients suffering from chronic pain grows longer doctors have been handing them out in greater numbers.
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A review by the National Treatment Agency for Substance Abuse, published in June, found a six-fold increase in the prescribing of opioid analgesics by GPs from 228 million items in 1991 to 1.38bn items in 2009.
Brian Iddon, the former chairman of the All Party Parliamentary Group on Drug Misuse, which reported in 2009, warned that the UK faced a similar epidemic to that in North America within a decade. Des Spence, a GP in Glasgow, wrote in the BMJ that the increased prescribing of opioids for chronic pain – other than that caused by cancer – was a "disaster in the making".
The increase is being driven by drug-company marketing that is fuelling patient demand. As populations age in the UK and across Europe, and more succumb to conditions such as arthritis, between 20 and 50 per cent are estimated to suffer from chronic pain.
Chronic pain caused by injury or disease has been poorly treated in the past and specialists acknowledge the growing use of powerful painkillers is a sign of a more compassionate society, prepared to dispense comfort to those in need. But there is a risk, as doses rise and dependence grows, that the dangers outweigh the benefits.
The review, Addiction to Medicines, by the National Treatment Agency for Substance Abuse, found that 3,735 patients receiving treatment for addiction said their primary problem was with prescription medicines, just 2 per cent of the total in drug-treatment services.
But the authors admitted that most of those with such a problem would be likely to seek treatment from their GPs.
Dr Cathy Stannard, a consultant in pain medicine at North Bristol NHS Trust and the author of Opioids in Chronic Pain, said: "There has been a huge increase in prescribing of opioid painkillers and they are being overused. I run a pain clinic where patients are coming in on 10 times the recommended dose. They keep going back to their doctors complaining of pain and the doctors don't know what to do – so they increase the dose.
"With other conditions, if the drug isn't working, doctors stop it and try something else. But it doesn't seem to be common clinical practice for doctors to say, 'if this painkiller isn't working we should stop it'."
Dependence on painkillers in the UK remained a hidden problem because there was "absolutely no data", Dr Stannard said.
The Public Health minister Anne Milton said: "Next month, we will convene a round-table meeting of experts to discuss action needed in light of new evidence from two recent Department of Health commissioned studies on addiction to prescription medicines. We will discuss how healthcare professionals can best address the issue."