A wafer that slowly releases painkilling medication as it dissolves inside the body could help recovery after knee replacement surgery.
About the size of a 20p piece, the implant is sewn into the new joint during the operation, which is performed on around 100,000 NHS patients a year.
Inside each wafer – made from the same material as dissolvable stitches – is 500mg of bupivacaine, a local anaesthetic widely used in dental procedures and childbirth.
As the wafer slowly degrades over three to four weeks, the bupivacaine seeps out on to surrounding nerve endings in the knee, blocking pain signals.
The dose released is highest in the first few weeks after surgery when pain is usually at its worst.
A wafer that slowly releases medication could help ease pain following knee replacement surgery (file photo)
Allay Therapeutics, the US firm which developed the wafer, is also planning trials in patients needing other joint replacements and abdominal surgery.
British doctors trialling the wafer – named ATX101 – are hopeful it will eventually allow thousands of NHS patients to cut back on opioid drugs, such as morphine, routinely used to control the pain after joint replacement operations.
Although effective at controlling pain, morphine and other opioids wear off within 24 hours and can trigger side-effects, from nausea to breathing problems and dependence, even after a few days’ use.
‘A small but significant proportion of patients can get addicted to opioids,’ says Professor Hemant Pandit, an expert in hip and knee surgery at the University of Leeds and Leeds Teaching Hospitals NHS Trust, who is leading the UK arm of an international trial involving the pain-relieving wafer.
‘The aim is to reduce or even nullify the need for knee replacement patients to take opioids.’
Around nine million people in the UK have osteoarthritis, where the protective cartilage in a joint breaks down – leaving bone rubbing on bone, causing pain and problems moving the joint. It often develops from wear and tear, although other risk factors include being overweight and sports injuries.
While anti-inflammatory painkillers and steroid injections can help, many will end up needing a knee replacement – and opioid drugs such as morphine, oxycodone and tramadol are the mainstay in tackling the pain after surgery.
But as well as severe side-effects, the drugs often need to be taken several times a day to be effective.
File photo of a surgical team operating on a patient. The new wafer is expected to give round-the-clock relief for up to a month following a procedure
The wafer, however, is intended to provide round-the-clock relief for up to a month. It is designed to dissolve in such a way that it releases half the drug content in the first few days then smaller amounts as the pain subsides.
A recent trial involving 112 patients from the UK, Canada and Australia – yet to be published in a medical journal – showed 22 per cent of those given the wafer needed no opioids during their recovery from knee surgery, compared to just 2 per cent in those who did not get it.
They were also able to stand sooner after the operation, climb stairs more quickly and got better sleep than those relying on strong painkillers.
A bigger trial involving around 200 patients is now being planned.
Dr Wendy Holden, a consultant rheumatologist and medical adviser to the charity Arthritis Action, said the wafer ‘seems much better at reducing pain and is great news for patients. Hopefully it will soon be available on the NHS’.