Tramadol is not effective for everybody
The painkiller tramadol (a synthetic opioid) is often used to help with post-operative pain as well as being prescribed for conditions such as arthritis, but in five to 10 per cent of patients, it doesn’t work effectively. Now a team of French researchers have developed a simple blood test that can quickly identify those people who won’t get full pain relief from tramadol.
An enzyme in the liver (CYP2D), metabolises, or breaks down, tramadol and produces a small molecule called O-demethyltramadol (ODT). This technical side of the process may seem complicated, but it is extremely important, because when tramadol is metabolised, it is two to four times better at reducing pain than when it hasn’t been successfully broken down. This is because ODT binds to human opioid receptors better, and that’s what blocks out pain signals.
“In our hospital we frequently use tramadol after surgery – about 50 – 60 per cent of patients are treated with it, while the rest are treated with nefopam, which is a non-opioid painkiller,” said Dr Laurent Varin, an anaesthetist at the Caen Teaching Hospital in France. Dr Varin presented the findings from this research at the Anaesthesiology Congress in Paris yesterday (10. 6. 2012).
“However, in about 5-10 per cent of Caucasian patients the CYP2D6 enzyme is inefficient and does not produce enough ODT to bind effectively to the opioid receptors; these patients are known as ‘poor metabolisers’ and will have poorly controlled pain unless the problem is identified quickly and they are switched to morphine or nefopam.”
Dr Varin and his colleagues recruited 294 patients who were given tramadol for pain relief after surgery for a range of digestive conditions and after operations on their spleen, gall bladder or pancreas. They took blood samples from the patients 24 and 48 hours after their operations, and tested them for concentrations of tramadol and ODT.
The research also studied the patients’ genes to help them identify their DNA make-up, and find out which patients in the study had inefficient enzyme CYP2D6. They discovered that eight per cent (23) of the patients were “poor metabolisers.”
According to Dr Varin, this simple and cheap test will enable doctors to provide the most effective pain relief for their patients. “If a patient is suffering unrelieved postoperative pain and the blood test reveals an ODT/tramadol ratio of less than 0.1, then the clinicians can switch quickly to morphine, rather than trying to increase the dose of tramadol and risk adverse drug effects by overdosing.”
“Furthermore, once a patient has been identified as a ‘poor metaboliser’, this means that other drugs that are also metabolised via CYP2D6 will be less effective, such as codeine and, to a lesser extent, oxycodone, and so this knowledge will help clinicians to decide on alternative treatment strategies for their patients,” said Dr Varin.
As patients we play a part in our own care and, in this case, it is simply a matter of speaking up. If you are in pain after an operation it’s important to let your nurse and doctor know, so that they can try another approach to your pain relief. It’s no time for suffering in silence. Similarly, if you have been prescribed tramadol for any other reason, do talk to your GP if you don’t think you are gaining much benefit from it.