Arsenic trioxide (
As(2)O(3)) has been widely accepted as the second-best choice for the treatment of relapsed and refractory
acute promyelocytic leukemia (APL) patients. However, a few studies have been conducted on a detailed speciation of
As(2)O(3) metabolites in blood samples of patients. To clarify the speciation of
arsenic, the blood samples were collected at various time points from a patient with APL after
remission induction therapy and during consolidation
therapy. The total amounts of
arsenic in blood cells and plasma, and the plasma concentrations of inorganic
arsenic and methylated metabolites were determined by inductively coupled plasma mass spectrometry (ICP-MS) and high-performance liquid chromatography/ICP-MS, respectively. The total amounts of
arsenic in the blood cells were 4-10 times higher than those in plasma. Among all
arsenic metabolites, the pentavalent
arsenate (As(V)) in plasma was more readily eliminated. During the drug-withdrawal period, the initial plasma concentrations of trivalent
arsenic (As(III)) declined more rapidly than those of
methylarsonic acid and dimethlyarsinic
acid, which are known as the major methylated metabolites of As(III). On the other hand, during the consecutive administration in the consolidation
therapy period, the plasma concentrations of total
arsenic and
arsenic metabolites increased with time. In conclusion, these results may support the idea that methylated metabolites of
As(2)O(3) contribute to the efficacy of
arsenic in APL patients. These results also suggest that detailed studies on the pharmacokinetics as well as the pharmacodynamics of
As(2)O(3) in the blood cells from APL patients should be carried out to provide an effective treatment protocol.