Beta interferon and azathioprine

OBJECTIVES: To evaluate safety and
efficacy of add-on low-dose azathioprine or interferon (IFN)-beta in MSers with active MS despite monotherapy.
METHODS: This retrospective
observational study evaluated 5-year data from 85 MSers with active
MS despite monotherapy with either IFN-beta or
azathioprine, who received add-on azathioprine or IFN-beta,
respectively. In a subgroup of 23 patients, 10-year data were analysed.
Clinical (relapse frequency, disability) and laboratory effects were
compared preceding and following the addition of second drug and between
the two treatment regimens. Potential serious adverse events were
RESULTS: The add-on treatment
triggered a drop in annualised relapse rate by approximately 1.5 points
sustained over 5 and 10 years. No effect on disability was observed.
Simultaneously, white blood cell and lymphocyte counts decreased, being
below the physiological levels in 8% and 13% of patients at each
time point, respectively. The drop in relapse rate was independent from
the dosage of azathioprine or changes in lymphocyte count. Comparison
between the two treatment regimens showed that, with the exception of
lymphocyte count, these effects were triggered by the add-on of
interferon but not azathioprine. The combination therapy was well
tolerated; however, after 5 years on treatment a moderately increased
incidence of cancer was observed.
CONCLUSIONS: IFN-beta as add-on to
azathioprine decreases relapse activity in active MS. In
contrast, azathioprine add-on in patients with suboptimal response to
IFN-beta does not improve the control over the disease activity.

How azathioprine works!

“This is a retrospective study that is uncontrolled and observational. This is why we do randomised, double-blind, placebo-controlled trials that are adequately powered. What does the statement “moderately increased incidence of cancer was observed” mean? Compared to what? The effectiveness of azathioprine in MS is unproven; it is a pity as it a cheap drug and relatively easy to use. If we knew then, what we know now, we would have done properly powered azathioprine studies and could have saved the NHS millions of pounds. May be in another lifetime, or parallel universe, azathioprine will get showing.”

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