Why Do TDM?
“The two main reasons why somebody would go on to detect drug levels: The first may be to assess medication adherence, and this applies virtually to any drug that rheumatologists use; the second reason is to optimize dozing, either for efficacy purposes or to prevent toxicity,” Balevic said.
“When it comes to optimizing dosing, you should really think about TDM as one tool in our toolbelt,” he said.
Dose is “just a surrogate,” he said. “When we prescribe a drug, what truly matters is the amount of active unbound drug at the site of action. That’s what’s responsible for a drug’s pharmacologic effect.”
However, the same dose, or even the same weight-based dose, does not necessarily mean similar patients will achieve the same amount of exposure to the drug, but TDM can help determine that, he said.
What’s Next
Studies into the use of TDM in rheumatology are ongoing. Brun said her group is currently conducting a cost-effective analysis from the NOR-DRUM trials.
“There’s going to be more studies coming out in the next few years, looking at what impact the use of therapeutic drug monitoring might have on outcomes,” Wallace said.
“As we accumulate more and more evidence, we might see organizations like ACR and EULAR start to weigh in more on whether or not therapeutic drug monitoring can or should be used.”
Petri, Brun, and Garg had no relevant disclosures. Wallace disclosed financial relationships with Amgen, Alexion, BioCryst, Boehringer Ingelheim, Bristol Myers Squibb, Medpace, Novartis, Sanofi, Viela Bio, Visterra, Xencor, and Zenas. Balevic disclosed relationships with the National Institutes of Health, the Childhood Arthritis and Rheumatology Research Alliance, and UCB.
A version of this article appeared on Medscape.com.