New blood test could help clinicians to identify the best drug dosage against rheumatoid arthritis.
A simple blood test may reveal the optimal dosage of the common drug Leflunomide, used for the treatment of rheumatoid arthritis (RA), a new study found.
The study, published in the journal Arthritis Care & Research, suggests that blood and genetic markers should be measured in all patients with RA before prescribing Leflunomide.
Currently, dosages of Leflunomide are arbitrarily prescribed to patients with RA, with variable results in response, due to physiological variability between patients in the way they metabolise the drug.
“Blood concentrations of Leflunomide are highly variable and unpredictable between patients, so we need to find the sweet spot for each person where we see a good response and minimal side effects, rather than adhere to the existing one-size-fits-all approach,” said Associate Professor Michael Wiese, from the University of South Australia, who led the study.
About the findings
Rheumatoid arthritis is an autoimmune condition causing inflammation and pain around the joints and affecting about half a million Australians. There is no cure for this condition, but drugs such as Leflunomide can alleviate symptoms and slow disease progression.
However, giving the wrong dosage to a patient can result in reduce effectiveness, increased side effects and wasteful spending.
“Leflunomide may not work for all patients, depending on their genetic makeup, but if we had a clear indicator whether a dosage change is necessary or if a new drug would be more appropriate, that would save patients a lot of money and some unnecessary side effects. A blood test is the key.”
Identifying the optimal dose for Leflunomide could translate into more effective treatment of RA and may also lead to significant reductions in costs. According to Prof Wiese, an increasing number of patients are being prescribed expensive biological drugs, which currently cost Australian taxpayers about $383 million each year and carry severe side effects.
However, older RA drugs, such as Leflunomide can be just as effective as these new drugs, at a fraction of their price. For example, older drugs such as Leflunomide are available for about $100-$500 a year per patient.
“People are quite excited about these expensive biological drugs, but the older drugs can be just as effective and far cheaper on the public purse, particularly if we can establish correct dosages for patients,” Prof Wiese said.
“Some individuals should be on the biological drugs, but we need to be smarter about who is selected for which drug. A blood test will determine who is more likely to respond to Leflunomide based on their genetic makeup,” he added.