[Greg]

Cytoxan, oral versus IV

by Greg on Sat May 15, 2010 1:17 pm

Hi Dr. Hofmeister,

Thank you for taking my question. I would like to know whether there are any differences in the side effects and efficacy of IV cytoxan versus oral cytoxan. I currently take cytoxan through IV when I go for Velcade. My doctor insists that I get it through IV, even though I have to sit in the infusion room for much longer and am billed for the administration. Even more important, I have heard that the side effects of this drug might be worse if given through IV intsead of orally. Is this true? Would you please comment on these issues?

[Dr. Craig Hofmeister]

Re: Cytoxan, oral versus IV

by Dr. Craig Hofmeister on Sat May 15, 2010 11:35 pm

Cytoxan (cyclophosphamide) is just standard chemotherapy. The are different side effects in that oral cytoxan can cause more GI symptoms but that's simply because it's a pill. In general the side effects are similar, but IV cytoxan often reaches higher serum levels and hence the side effects are usually more extreme -- for myeloma patients, we generally give 1000 mg/m2 or 500 mg/m2 and this can cause significant low white cells, red cells, and platelets. That said you can reach the same therapeutic and side effects if you just take a higher dose orally; unfortunately there is not a 1:1 conversion and hence I don't know that 500 mg by mouth is equivalent to 300 mg IV.

Donna Reece and her group at Princes Margaret Hospital in Toronto have published extensively about the use of oral cytoxan in combination with Velcade and dexamethasone for just the reasons you have documented -- wanting something convenient and oral.