There have been considerable advances made recently in the treatment of mul
tiple sclerosis (MS). In particular, interferon (IFN)beta has been demonstr
ated in several independent, multicentre clinical trials to lower unequivoc
ally the biological activity of this illness. The results of these trials h
ave been remarkably consistent, demonstrating a reduction in both disease a
ctivity and cumulative disability, using a combination of clinical and magn
etic resonance imaging outcome measures. Nevertheless; the importance of th
e total weekly IFN beta dose in the clinical management of individual patie
nts has been controversial.
However, there is considerable information available regarding the effect o
f IFN beta dose on the various biochemical and clinical markers that are af
fected by IFN beta, which is derived both from pre-clinical studies and mul
ticentre clinical trials. On balance, convincing evidence is provided to su
pport the notion that there is a clinically relevant dose-response in the u
se of IFN beta to treat patients with relapsing/remitting MS. However, many
of the clinical trials of IFN beta in MS have confounded the potential eff
ects of dose with the possible effects of frequency of IFN beta administrat
ion. As a result, it is possible that the apparent dose-response observed i
n these clinical trials may be due, in part, to the more frequent dose admi
nistration schedule rather than the total weekly dose.