Background: Data on ER and IV POS among organ transplant recipients (OTRs) are limited, and the role of TDM is unclear.

Methods: Retrospective study of patients (pt) receiving any formulation of POS who had serum troughs checked. Therapeutic was defined as >= 1 mcg/mL.

Results: We analyzed 88 pt and 340 levels (SUS: 88, ER: 197, IV: 55). 85 pt were OTRs (97%), 73 were lung transplant recipients (LT) (83%), 17 had cystic fibrosis (CF) (19%). Concentration/dose ratios were lower with SUS vs ER/IV (p < 0.0001) but were similar in ER/IV groups (p=0.51). There was no difference in serum levels between pt receiving ER vs IV POS at 300 mg once daily (median 1.2 vs 1.3 mcg/mL, therapeutic 70% vs 73%, p = 0.57 and >0.99, respectively). 3 pt had levels [pound] 0.2 mcg/mL on 300 mg ER: 2 had CF and had undergone LT (0.2 and 0 mcg/mL) and 1 had short-gut syndrome (0.1 mcg/mL). 66% and 67 % of pt receiving ER or IV POS (300 mg once daily) achieved initial therapeutic levels, respectively; of these, 87% and 83% had median therapeutic follow-up levels, respectively. Serial levels were available for 7 pt whose dose was increased from 300 to 400 mg ER once daily for subtherapeutic levels. 4/7 pt achieved therapeutic levels on 400 vs 0/7 on 300 mg ER once daily (p = 0.069). Metoclopramide use and CF were associated with subtherapeutic vs therapeutic levels (25% vs 4% and 37% vs 13%, respectively, p = < 0.05). When pt with CF were excluded, neither age nor body mass index were associated with POS levels. CF pt had lower levels than non-CF pt on a dose of 300 mg ER once daily (median 0.8 vs 1.3 mcg/mL, p = 0.018).

Conclusion: Therapeutic levels are more reliably achieved with ER & IV POS vs to SUS POS. Serial TDM is unnecessary for most, except for pt with CF or those on metoclopramide. Dose increases may effectively increase levels. Novel dosing strategies are needed for CF.

CITATION INFORMATION: Haidar G., Shields R., Clancy C., Nguyen M. Therapeutic Drug Monitoring (TDM) of Suspension (SUS), Extended-Release (ER), and Intravenous (IV) Posaconazole (POS) at a Large Transplant Center Am J Transplant. 2017;17 (suppl 3).

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