What is your approach to timing of medications like Rituximab and Cyclophosphamide around plasmapheresis in patients on daily PLEX?

Plasma exchange (PLEX) in designed to remove antibodies. Thus, PLEX will remove monoclonal antibodies, including rituximab, and do so fairly effectively and likely to some extent in proportion to the intensity of the PLEX. If there is a clinical need to use PLEX for a patient also to be given rituximab, a reasonable practice is to give rituximab but wait at least 48 hours before the next session of PLEX and then give the next dose of rituximab after the course PLEX is competed (usually up to two...

Agree. Cyclophosphamide is inactive as administered and metabolized to multiple active compounds with differing effects and a half lives, none of which can we reliably measured. Hence, the effect of renal insufficiency is not well understood. An empiric measure of the effect that has been employed is the development of a mild leukopenia (WBC approx 3500) 10-14 days after monthly bolus cyclophosphamide. This does not apply to daily oral cyclophosphamide administration; the conventional practice h...

The pharmacokinetics of cyclophosphamide in patients with renal impairment is not well studied; thus, the dosing in such a situation is not standardized. However, some general guidelines have been incorporated into clinical trials for the treatment of patients with ANCA-associated vasculitis. These approaches are useful to clinicians. For patients on dialysis, and likely any form of renal-replacement therapy (other than transplantation), it is reasonable to start with half the dose one would use...

Thank you for the wonderful response, @Dr. First Last.

Agree with timing of cyclophosphamide after hemodialysis. Do you have any thoughts on how to administer cyclophosphamide on patients on continuous renal replacement, such as CRRT (have heard varied opinions: wait until after CRRT or that given the continuous nature of CRRT it should not cause significant removal and okay to administer while on CRRT)?