Biologic drugs, including TNF inhibitors, have been shown to reduce pain and improve productivity in people with ankylosing spondylitis (AS). But feeling better isn’t always as simple as getting a prescription and sticking with it. According to a new study, less than half of AS patients are still taking the same TNF inhibitor five years after starting it.
The study, published in the journal Arthritis Research & Therapy, was an observational trial of 2,590 AS patients in a Swedish rheumatology database who had started their first TNF inhibitor between 2006 and 2015. The researchers, based at the Karolinska Institute in Stockholm, tracked everyone in the study until the end of 2015 to see how their medication regimen had changed during that time.
According to their findings, the majority of TNF inhibitor users (74 percent) were still on the same drug after a year. But five years later, that number had dropped to 46 percent. Many who had stopped using the first medication had since switched to a different biologic, but 30 percent were no longer using any disease-modifying drug.
The authors did not speculate as to why so many patients had switched biologics or why some of them had stopped using them entirely, though side effects or discomfort might have played a role. TNF inhibitors, which block a protein that would otherwise lead to excess inflammation, have to be taken by injection or infusion, and some patients develop a rash or burning sensation around the injection site. Side effects may also include allergic reactions and an increased risk of serious infections like tuberculosis.
It’s possible that some patients stopped because they had gone into remission, though that might be risky because AS — a type of inflammatory arthritis that causes severe back pain — is a chronic condition and AS relapses are common. Lack of efficacy might also be a reason to make a change; someone using a TNF inhibitor would likely switch or stop if a drug did not control their symptoms.
“These findings … highlight the need for thorough follow-ups to target patients with AS who are non-responsive to [TNF-inhibitors], and to determine predictors for such non-response, as well as alternative treatments options,” the authors wrote.
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