Cyclophosphamide is another immunosuppressive drug that has been used in MS treatment for many years. Its early use was mostly in uncontrolled studies in which it was often, but not always, reported to improve the condition of patients with chronic progressive MS, especially those with only modest disability at the beginning of treatment. The largest trial performed, a Canadian multicentre study, failed to demonstrate benefit. A number of incompletely blinded, uncontrolled studies continue to suggest that intensive immunosuppression with cyclophosphamide may reduce clinical and MRI evidence of aggressive disease activity in selected patients. Cyclophosphamide has many side-effects, including hair loss, nausea and vomiting, haemorrhagic cystitis, infertility, and risk of infection. Some clinicians still use cyclophosphamide as a “booster” in rapidly progressive patients, based on reports that it may stabilise the disease. Careful monitoring of the patient, including blood cell counts, liver function tests, and urinalysis, is necessary throughout the course of treatment.

In the opinion of the Committee, there remains considerable controversy about the merits of this drug in MS in the absence of positive results from large, randomised, and controlled studies. Because its use carries significant risk, if it is to be administered, it should only be done in specialised centres and only to patients with treatment refractory, clinically active MS.