How well do blood levels correlate with intracellular levels?
In a recent population pharmacokinetics study conducted in chronic myeloid leukemia and gastrointestinal stromal tumor patients, the imatinib cell/plasma ratio was determined to be 8:1. This ratio remained stable over time, and was consistent with in vitro data in the literature, leading the investigators to conclude that “measuring plasma imatinib concentration … probably provides a good surrogate for intracellular exposure to the drug.” [Widmer N et al. Br J Clin Pharmacol. 2006;62:97-112.
