Scientists have identified the opioid painkiller drugs that may put patients most at risk of a fatal overdose.
Researchers from the University of Manchester have found that fentanyl is most strongly linked to respiratory depression – the condition that causes death from overdose.
It causes breathing to become too slow or shallow, causing oxygen levels to drop and toxic carbon dioxide to gather in the blood.
Opioids – a group of strong painkillers used to treat pain after surgery or injury and in people with cancer – have long been known to trigger it.
The drugs, which include morphine, codeine and tramadol, interfere with signals in the brain that control breathing, causing a dangerous deficiency in oxygen.
The findings come amid Britain’s opioid epidemic, with prescriptions doubling over the past 25 years – a rise that’s said to be driven by a surge in addiction.
Today, they are prescribed to around 3.3million adults in the UK to treat a range of problems such as severe joint pain, surgery-related injuries and cancer pain.
They are also used commonly as anaesthetics during operations.
Researchers from the University of Manchester say that among non-cancer patients, fentanyl was most strongly linked to respiratory depression
Researchers of the study, published in BMC Medicine, aimed to analyse which opioids were most linked to life-threatening harm – particularly among those who were prescribed opioids for non-cancer pain.
They analysed electronic health records from 32,909 UK adult patients being treated in hospitals in north-west England.
The researchers used medical tests to look for signs that patients’ breathing had become dangerously slow.
They did this by analysing breathing rate, oxygen levels and whether patients needed naloxone – a medicine that reverses the effects of an opioid overdose.
Their method also allowed them to track when opioids had been administered.
When compared to patients who had taken codeine, those taking fentanyl were three times more likely to suffer breathing problems.
Patients given fentanyl were also 85 per cent more likely to suffer respiratory depression than morphine patients.
The scientists also found that taking more than one opioid at the same time trebled the risk of the deadly complication.
Those on oxycodone and morphine were also seen to have a significantly higher risk of breathing problems when compared with codeine.
And those taking combinations of opioids also had around a 50 per cent higher risk than those taking morphine alone.
The researchers say fentanyl may be particularly risky because it is much stronger than other opioids and reaches the brain very quickly, suddenly slowing breathing.
The study also found that people with chronic obstructive pulmonary disease (COPD) may be most vulnerable to potent opioids.
Among this group, fentanyl was linked to about four times the risk of breathing problems compared with codeine, suggesting people with long-term lung disease may be especially vulnerable.
Dr Meghna Jani, a senior clinical lecturer at the University of Manchester, and senior author of the study, said: ‘Opioids remain important medicines for managing severe acute pain.
‘Our findings show that the risks are not the same across all opioid drugs or doses.’
The study found that higher opioid doses were linked to greater risk.
Even people taking moderate doses (31–60 MME per day) had a higher risk.
The risk increased further when opioids were taken with gabapentinoids such as gabapentin or pregabalin – commonly prescribed for nerve pain and epilepsy.
Growing concerns about opioid dependence in the UK prompted the Medicines and Healthcare products Regulatory Agency (MHRA) to issue safety guidance on the risk of addiction and dependence last year.
Meanwhile, it is estimated that between 82,000 and 90,000 patients each year overdose on paracetamol – which can lead to liver failure.
This can lead to yellowing of the skin or eyes, low blood sugar, sweating, shaking, confusion or irritability, clumsiness, feeling or being sick, extreme tiredness and stomach pain.
Last November, a coroner sounded the alarm over inadequate safety checks by medicines wholesalers after a man died of an overdose from painkillers he bought without any checks.
