#28: Serum Posaconazole Concentrations Among Children, Adolescents, and Young Adults Receiving Delayed-Release Tablet And Intravenous Posaconazole

Abstract

Abstract Background Posaconazole is a broad-spectrum antifungal used for prophylaxis and treatment of invasive fungal infections. There are limited data on the optimal dosing, safety, and effectiveness of the delayed-released tablets (DRT) and intravenous (IV) formulations in immunocompromised pediatric and adolescent patients. Methods A retrospective chart review was performed to study all immunocompromised patients who received DRT or IV formulations of posaconazole at our institution from January 1, 2014, to July 31, 2019, and had at least one plasma trough concentration. Plasma concentrations ≥0.7 µg /mL were considered therapeutic for prophylaxis, and ≥1.0 µg/mL for treatment. We describe our experience including dosing, plasma trough concentrations, safety, and tolerability. Results We identified 54 patients (28 males/26 females) who received DRT or IV formulations of posaconazole. The median age was 14 years (range 2–21 years). Thirty-one (57%) patients received posaconazole for treatment and 23 (43%) for prophylaxis. The most common underlying condition was hematological malignancies (66%) and 19 patients (35%) had received an allogeneic HSCT and were receiving immunosuppressive therapy. Overall, 36 (67%) patients achieved targeted initial plasma trough concentrations (median 1.3 µg/mL, IQR 0.758–1.760 µg/mL) (Figure). The median daily dose among patients <13 years of age who achieved the targeted initial plasma trough concentrations was 7.3 mg/kg/day (IQR 6.8–11.0) for the DRT formulation and 9.8 mg/kg/day (IQR 7.4–11.7) for the IV formulation. The median daily dose among patients ≥ 13 years of age who achieved the targeted initial plasma trough concentrations was 4.9 mg/kg/day (IQR 4.1–6.5) for the DRT formulation and 5.6 mg/kg/day (IQR 3.9–5.8) for the IV formulation. Concomitant use of H2-receptor blockers (H2RA) and/or proton pump inhibitors (PPI) medications were not associated with failure to achieve target trough levels (P = 0.96). Thirty-six patients (67%) developed transaminitis, mostly grade 1. Conclusions Our results show that DRT and IV formulations are safe and effective in immunocompromised children, adolescents, and young adults. Higher dosing per body weight of DRT and IV posaconazole may be required in patients <13 years of age compared with patients 13 years of age and older to achieve therapeutic plasma concentrations. It appears that neither a PPI nor an H2RA has an effect on the plasma exposure of the DRT.