Therapeutic drug monitoring should play an important role in determining and maintaining the most optimal dose of anti-TNF agents for IBD patients, but needs MBS rebates to be more accessible, an expert says.
Conjoint Associate Professor Susan Connor, senior staff specialist at Liverpool Hospital’s Department of Gastroenterology and Hepatology, presented to AGW 2016 held in Adelaide last week.
She said studies were still ongoing but the effective use of biologic therapeutic drug monitoring (TDM) had already been established when patients have a loss of response while on treatment and also in establishing the appropriateness of dose de-escalation.
There was also evidence suggesting it provided useful information early after induction and during the maintenance phase, she said. It could also be helpful before recommencing treatment after a drug holiday.
The Australian Inflammatory Bowel Disease Association (AIBDA), a branch of the Gastroenterological Society of Australia (GESA), is currently overseeing the preparation of a consensus statement on the appropriate use and interpretation of TDM for anti-TNF agents.
Professor Rupert Leong, a senior staff specialist gastroenterologist, Director of Endoscopy and Head of the Inflammatory Bowel Disease Service at Concord Hospital, Clinical Professor of Medicine at University of Sydney and UNSW, and founding director of IBD Sydney, Australia, is overseeing this project.
A result is expected in early 2017, which members hope will provide the necessary local evidence to obtain MBS rebates for TDM of anti-TNF agents.
After her presentation, which was packed by delegates, Professor Connor said monitoring of infliximab drug levels was invaluable in the management of patients with IBD. She said there was more than just weight to consider when establishing the correct dosage for each patient.
Gender, BMI, abdominal obesity, inflammatory burden and C-reactive protein (CRP) levels also play a role.
Drug concentration is also influenced not only by dose but also by how the drug is absorbed, distributed, metabolised, and eliminated by the body, and this will vary between individuals.
“One size doesn’t fit all and one dosage doesn’t fit all,” she told the limbic. “Each person uses the drug in a different way and that’s there TDM comes in.”
Professor Connor said achieving optimal therapeutic drug concentration was associated with improved mucosal healing and reduced CRP levels.
She said her local area health service was currently using its own funds to provide TDM for IBD patients, and while this provided a short-term solution, it would be ideal to have it funded through the MBS.
“It’s costly (the test), but if you think about how much we are spending on biologics in Australia, this is very cheap in the context of what is being spent,” she said.
One of the major hurdles to overcome is the fact that some patients who undergo TDM will require drug escalation and she believes this is the “can of worms” that might prevent a favourable outcome with MSAC.
“Even though it’s been shown to be cost-effective, there will still be patients who will be drug escalated, but there will also be patients who can be de-escalated,” she said.
“The important thing it will show is where biologics are being used inappropriately. And if you do the test that demonstrates they need more drug you need to give more drug. But some people might need less.”