Nathan Punwani, Blood and Marrow Transplant Physician at Mayo Clinic, shared a post on X:
“During induction chemo for AML, why do we give continuous IV cytarabine, instead of bolus dosing like in consolidation?
Cytarabine is a pyrimidine analog that inhibits DNA synthesis. The chemo kills cells that are undergoing active DNA replication, making cytarabine ‘S-phase specific’. But leukemia cells are constantly in flux in the cell cycle.
They are not all uniformly in the same cell cycle phase. In active AML, leukemia blasts are slowly entering S phase over days, and cell kill is enhanced when they are getting continuously exposed to IV cytarabine.
Once patients achieve remission, we do high dose bolus cytarabine to consolidate that remission.
Bolus dosing generates high peak plasma concentrations and elevated intracellular levels of cytarabine metabolites (Ara-CTP) to overwhelm resistance mechanisms that characterize residual AML.
Bolus dosing produces high peak concentrations, but exposure is transient as plasma cytarabine has a short half life (10-15 min) due to rapid deamination.
So continuous IV yields low peak concentrations but prolonged duration above effective concentration, vice versa for bolus.
Effectively, one should think of continuous IV and bolus dose cytarabine as Two Different Drugs With Radically Different Mechanisms of Action!”
Other articles featuring Nathan Punwani on OncoDaily.