(RxWiki News) Tramadol, marketed as Ultram in the US, is an opioid pain medication that works like morphine. In about five to 10 percent of people, tramadol does not work well.
Tramadol is commonly used in treating many different pain conditions and after surgery. At a recent conference, researchers reported that a simple blood test could detect who would not respond well to tramadol.
"Tell your doctor about your pain symptoms."
A recent study, led by Laurent Varin, MD, of the Caen Teaching Hospital in Caen, France, enrolled 294 patients who had recent gastrointestinal surgeries, on organs like the spleen, stomach and gall bladder.
All the patients in the study were given tramadol after surgery to control pain.
Tramadol requires an enzyme called cytochrome p450 2D6 to metabolize it – meaning break it down into parts. The metabolites of the drug are more effective at binding to opioid receptors, so they produce the most effective pain relief.
People lacking this enzyme are not able to break down tramadol into its more effective pieces and would be expected to show higher levels of tramadol in their blood and none of the metabolites.
Dr. Varin’s study used blood tests 24 and 48 hours after surgery to measure the level of tramadol and its metabolites in the blood. People with low levels of metabolites were considered to be lacking the enzyme and not responsive to the pain medication.
They also looked at the genes of people to see who was lacking the enzyme. About 8 percent of the people in the study were lacking the enzyme. They then compared the blood profiles to the genes.
They found that the ratio of the tramadol to its metabolites in the blood could show which people were lacking the gene for this enzyme.
The authors concluded that people with blood ratio less than 0.1 after 24 hours on tramadol were not able to metabolize it.
When a person does not respond to tramadol, doses are often increased, which may raise the risk for side effects. The blood test could eliminate some of the guesswork for doctors.
Other drugs that need the same enzyme, like codeine, are also less effective for people lacking this enzyme, so the test has long-term benefits for helping doctors make better drug choices for their patients.
The cost of the blood test is about $35 to $40.
The results of this study were presented Sunday, June 10 at the European Anaesthesiology Congress in Paris, France.
This study has not been published in a peer-reviewed journal, so it may not have been reviewed for accuracy by other experts in the field.