High-dose cyclophosphamide in multiple sclerosis patients undergoing autologous stem cell transplantation.

High-dose cyclophosphamide (CTX) is commonly used in preparation for autologous and allogeneic stem cell transplantation. CTX is a pro-drug, which undergoes complex oxidative metabolism with the metabolites being eliminated both renally and hepatically. In the following study, we evaluated the pharmacokinetic characteristics of high-dose CTX in three patients undergoing autologous stem cell transplantation for multiple sclerosis. The plasma concentration-time profiles for CTX and its hydroxy-metabolite were similar in multiple sclerosis patients to those reported in cancer patients undergoing stem cell transplantation. There was an increase in drug clearance after the second CTX dose indicating that the drug induced its own metabolism consistent with reports in other populations receiving high-dose CTX. One of the three patients cleared the drug slowly but this was not associated with greater toxicity. The patient with the slow clearance value and therefore highest drug exposure had stable disability scores at 2 years posttransplant compared with baseline values taken prior to transplantation. In conclusion, in this small case series, there was no indication that CTX metabolism was different than that in other populations undergoing transplantation. Copyright 2002 Elsevier Science B.V.