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Tacrolimus (TRL) is an immunosuppressive drug characterized by a narrow therapeutic index, low bioavailability, and pharmacokinetic variability. Intravenous (i.v.) TRL may be needed whenever the oral route is unavailable. The small amount of infusion formulation (5 mg/mL) results in a large dilution and need for careful technical management of the infusion. This study addressed the feasibility to provide sublingual (SL) as an alternative to i.v.. TRL for transplanted patients. In a substudy, we performed a retrospective analysis of 17 lung and heart transplant patients using SL TRL. It included therapeutic drug monitoring and 4 area under curve (AUC) measurements. Patients received SL TRL on a dose-to-dose basis from the oral formulation. The mean age of the subjects (14 male, 3 female) was 35.3 ± 15.6 years; 146 trough (C(0)) samples were collected during the SL period (15.8 ± 20.6 days) showing a conformity level of 90.4%. Mean dose, C(0), and AUC of SL tacrolimus were 0.116 ± 0.096 mg/kg, 12.9 ± 5 ng/mL, and 230 ± 74 ng·h/mL, respectively, with an average 1 hour time to peak concentration. Acute rejection episodes, renal toxicity, and drug interactions were not observed. This study supported the convenience of short-term SL TRL administration, even in unconscious patients. Further investigations are needed to validate the dose range of the SL route., (Copyright © 2010 Elsevier Inc. All rights reserved.)

Voriconazole is an anti-fungal agent active against Aspergillus infection that is used for prophylaxis and curative treatment in lung transplant patients. We present nine cases of painful neuromuscular disorders, an unusual and rare side effect of high-dose voriconazole in association with tacrolimus.

Background. Aspergillosis is a high-risk complication in cystic fibrosis (CF) lung transplant patients. Azole antifungal drugs inhibit CYP3A4, resulting in significant metabolic drug–drug interactions. Voriconazole (VRZ) was marketed without therapeutic drug monitoring (TDM) recommendations, consistent with favorable pharmacokinetics, but regular determinations of plasma VRZ concentration were introduced in our center to manage interactions with calcineurin inhibitors and to document the achievement of therapeutic levels. Methods. VRZ TDM data analysis for trough concentration (C0) and peak concentration (C2) was carried out, using validated liquid chromatography assay with ultraviolet detection, for 35 CF lung transplant patients (mean age 25 years, mean weight 47 kg, balanced sex ratio) since 2003. Therapeutic range (C0: 1.5 ± 0.5 – C2 : 4.0 ± 1.0 mg/L) was expressed relative to pivotal pharmacokinetic trial data. Results. The duration of VRZ treatment ranged from 9 days to 22 months. The recommended standard dose of VRZ (200 mg twice a day, following the loading dose) resulted in significant plasma concentrations (>0.5 mg/L) in 20% of CF lung transplant patients. Therapeutic concentrations were obtained using higher doses (average 570 ± 160 mg/day, +43%, P<0.01). Despite adaptation, C0 remained <0.5 mg/L (11%), even when the drug was administered intravenously, highlighting the variability of VRZ pharmacokinetics, possibly enhanced by CYP2C19 polymorphism. The risk of inefficacy during periods of underdosage was overcome by treatment with antifungal drug combinations (caspofungin, n=10). The therapeutic index was limited by neurologic effects (14%) and hepatic abnormalities (30%). VRZ concentrations correlated significantly ( P<0.01) with aspartate aminotransferase levels but not with bilirubin levels. VRZ acted as a metabolic inhibitor of tacrolimus (C0 to dose ratio 5.8 ± 2.6, n=31/VRZ versus 1.7 ± 0.9 alone, P<0.001). Large changes in azole concentration affected the magnitude of the drug–drug interactions and adjustment requirements. Conclusions. TDM is required because VRZ levels are often undetectable in treated CF lung transplant patients, supporting the use of antifungal drug combinations until achievement of VRZ C0 at a steady state between 1 and 2 mg/L. Plasma VRZ concentrations should be determined for the quantitative, individualized management of drug–drug interactions in lung transplant patients, in particular immunosuppressant such as tacrolimus, considering VRZ to be both a target and an inhibitor of CYP3A4. [ABSTRACT FROM AUTHOR]