TORONTO — Less than half of MS patients prescribed disease-modifying drugs are still taking the medications after two years, researchers say.
A study of Ontario MS patients, published in the May issue of the Canadian Journal of Neurological Sciences, found that within two years of starting a self-injected drug, only 44 per cent were still taking the medications aimed at slowing progression of the disease.
Using an Ontario drug-coverage database, researchers identified 682 people newly prescribed one of four MS medications and followed them from April 2006 until March 2008. After six months, about a quarter had gone off their medication; at one year, 40 per cent had stopped their drug; and by two years, 56 per cent were no longer continuing with their prescription.
"To put it another way, the majority of people had gone off these drugs after two years, even though MS is a very chronic condition and typically requires years of treatment with these disease-modifying treatments," said principal investigator Dr. Paul O'Connor, a neurologist at St. Michael's Hospital in Toronto.
The study also found that adherence to the four different drugs didn't vary: patients stopped taking them at about equal rates.
The self-injected drugs are prescribed to people with the relapsing-remitting form of multiple sclerosis — they have no effect on patients with progressive forms of the disease, said O'Connor, suggesting there could be several reasons why adherence drops off over time.
"Many patients strongly dislike having to self-inject. Many also dislike side-effects that come with these drugs," he said. As well, they don't work for all patients.
Three of the drugs are interferon-based, working by suppressing inflammatory factors in the immune system. As a result, they can cause flu-like symptoms such as aching muscles, fatigue, fever and chills as well as pain and swelling at the injection site.
Patients expecting to feel better because they are taking a drug may actually feel worse, "even though they do slow down the disease and reduce the number of new (brain) lesions," said O'Connor.
Still, the authors say it's important for patients to try to stick with their drugs.
"This study shows that adherence to treatment ... is low, which is concerning given their proven effectiveness in slowing the progression of MS," said co-author Tara Gomes, an epidemiologist at the Institute for Clinical Evaluative Studies. "We need to increase the appreciation of the long-term benefits of these medications to ensure that MS patients are receiving the best treatment available."
The study did not look at compliance of patients taking Tysabri (natalizumab), another injectable MS medication, which was not covered at the time by the province's drug plan, so was not part of the database used by researchers.
Patients with relapsing-remitting MS now have the first oral drug to help reduce flare-ups of the disease. In March, Health Canada approved Gilenya (fingolimod), a once-a-day pill made by Novartis Pharmaceuticals.
However, O'Connor said the drug is even more expensive than the injectables — about $31,000 a year versus $20,000 to $24,000 — and is not covered by provincial health plans. It also has its own set of side-effects, some potentially serious, he said.
An estimated 55,000 to 75,000 Canadians have multiple sclerosis, a complex incurable disease of the central nervous system that can cause myriad symptoms, including fatigue, vision problems, loss of balance, and muscle spasms and weakness, says the MS Society of Canada.