Posaconazole oral suspension primary prophylaxis in acute leukemia and allogeneic stem cell transplant patients: can it be used without measurement of plasma concentration?

Posaconazole oral suspension (PCZ-susp) can display a variable degree of inter and intra-individual absorption. However, there is no agreement on the need of plasma-posaconazole-concentration (PPC) monitoring as a routine practice in patients receiving PCZ-susp. In this prospective, multicenter study we evaluated the variability of PPCs in hematologic patients receiving PCZ-susp prophylaxis with the aim to define conditions at different risk of subtherapeutic PPCs. Overall, 103 acute leukemia (AL) patients submitted to intensive chemotherapy (115 courses) and 46 allogeneic stem cell transplant (allo-SCT) recipients (47 courses) receiving PCZ-susp prophylaxis were considered. The adequacy of PPC pattern after the steady state (≥day 7 of treatment) in courses with two or more PPC measurements was defined as follows: inadequate pattern: PPC < 0.5 mcg/ml at least once; borderline pattern: PPC always ≥0.5mcg/ml but < 0.7 mcg/ml at least once; adequate pattern: PPC always ≥0.7 mcg/ml. The PPC pattern was evaluable in 83 and 37 AL and allo-SCT patients, respectively. It was adequate, borderline and inadequate in 63.9%, 14.5%, and 21.7% of courses, respectively, in AL, and in 62.2%, 10.8%, and 27.0% of courses, respectively, in allo-SCT. In both groups, an inadequate PPC pattern was associated with the development of diarrhea. In absence of diarrhea, the probability of an inadequate PPC pattern was 11.9% in AL and 17.2% in allo-SCT patients. PCZ-susp might be used without stringent need of PPC monitoring in patients without diarrhea.