Purpose The stability of 0.3-mg/mL tacrolimus ophthalmic solution at different storage temperatures was studied. Methods A sterile ophthalmic solution of 0.3 mg/mL tacrolimus was prepared in triplicate under aseptic conditions by diluting tacrolimus in eye drops. Three aliquots of this solution were transferred into polypropylene bottles and stored at 25, 2–8, or −15 to −25 °C. Samples were collected immediately after preparation and at selected time points and assayed in triplicate using high-performance liquid chromatography (HPLC). Samples were also visually examined for macroscopic changes. The 0.3-mg/mL tacrolimus solution was also exposed to acidic treatment and heat to force its degradation and to evaluate the selectivity of the analytic method. The tacrolimus ophthalmic solution was considered stable if at least 90% of the mean initial concentration remained when analyzed by HPLC. Results When stored at 2–8 °C and between −15 and −25 °C, at least 90% of the initial tacrolimus concentration remained throughout the 85-day study period. There were no significant differences in tacrolimus concentrations between the starting and ending points (p > 0.05). However, when tacrolimus solution was stored at 25 °C, the percentage of the initial tacrolimus concentration remaining had decreased to less than 90% on day 28. Conclusion Tacrolimus diluted to 0.3 mg/mL in eye drop solution was stable for 20 days when stored at 25 °C and for at least 85 days when stored at 2–8 °C or between −15 and −25 °C in polypropylene bottles and protected from light.

Background: To evaluate the adequacy of different dosing regimens of voriconazole for the prophylaxis of invasive candidiasis and aspergillosis in adult allogeneic stem cell transplant recipients by means of population pharmacokinetic (PK) modelling and simulation. Methods: Allogeneic stem cell transplant recipients receiving voriconazole were included in this observational study. A population PK model was developed. Three oral voriconazole-dosing regimens were simulated: 200, 300, and 400 mg twice daily. The pharmacodynamic target was defined as fAUC_0–24/0.7. A probability of target attainment ≥90% was considered optimal. The cumulative fraction of response was defined as the fraction of patients achieving the pharmacodynamic target when a population of simulated patients is matched with a simulated population of different Candida spp. and Aspergillus spp. The percentage of patients with trough plasma concentrations at steady state (C_trough) within the reference range (1–5.5 mg/L) was also calculated. Results: A 2-compartment PK model was developed using data from 40 patients, which contributed 237 voriconazole plasma samples, including trough and maximum concentrations. Voriconazole 200, 300, and 400 mg twice daily achieved probability of target attainment ≥90% for minimal inhibitory concentration values ≤0.25, ≤0.38, and ≤0.50 mg/L, respectively. The cumulative fraction of response for A. niger, A. versicolor, and A. flavus increased >10% when increasing voriconazole dose from 200 to 400 mg twice daily (from 72.5% to 89.5% for A. niger; from 77.7% to 88.7% for A. versicolor; and from 82.4% to 94.9% for A flavus). The percentage of patients with C_trough within the reference range increased 15% when voriconazole dose was increased from 200 to 300 mg twice daily. Conclusions: The PK simulations in this study suggest that transplant recipients on voriconazole prophylaxis against invasive candidiasis or aspergillosis are likely to achieve the target concentrations associated with the desired treatment outcomes if the maintenance dose is 200 mg twice daily. However, Aspergillus spp. with high minimal inhibitory concentrations could require higher maintenance doses.