Evaluation of the drug-drug interaction between triazole antifungals and cystic fibrosis transmembrane conductance regulator modulators in a real-life cohort.

Limited data on the clinical management of drug-drug interactions between triazoles and Cystic Fibrosis transmembrane conductance regulator (CFTR) modulators are available. We retrospectively evaluated azole target attainment and dose adaptations in patients from two Dutch CF centres concomitantly receiving triazoles and CFTR modulators. In total, 21 patients with 59 triazole trough concentrations were evaluated. Subtherapeutic concentrations were frequently observed, especially for itraconazole and voriconazole. Of the investigated antifungal agents, posaconazole appears the most preferable option. Our results emphasize the importance of adequate management of this interaction and underpin the added value of therapeutic drug monitoring of triazoles in this population.

Fungal infections are serious complications in Cystic Fibrosis (CF) patients. We evaluated patients concomitantly receiving triazoles and CF transmembrane conductance regulator modulators: subtherapeutic triazole exposure was frequently observed. Posaconazole appears the preferable antifungal agent.

Personalized Antifungal Therapy Through Model-Informed Precision Dosing of Posaconazole.

BACKGROUND AND OBJECTIVE: Posaconazole is a pharmacotherapeutic pillar for prophylaxis and treatment of invasive fungal diseases. Dose individualization is of utmost importance as achieving adequate antifungal exposure is associated with improved outcome. This study aimed to select and evaluate a model-informed precision dosing strategy for posaconazole. METHODS: Available population pharmacokinetic models for posaconazole administered as a solid oral tablet were extracted from the literature and evaluated using data from a previously published prospective study combined with data collected during routine clinical practice. External evaluation and selection of the most accurate and precise model was based on graphical goodness-of-fit and predictive performance. Measures for bias and imprecision included mean percentage error (MPE) and normalized relative root mean squared error (NRMSE), respectively. Subsequently, the best-performing model was evaluated for its a posteriori fit-for-purpose and its suitability in a limited sampling strategy. RESULTS: Seven posaconazole models were evaluated using 764 posaconazole plasma concentrations from 143 patients. Multiple models showed adequate predictive performance illustrated by acceptable goodness-of-fit and MPE and NRMSE below ± 10% and ± 25%, respectively. In the fit-for-purpose analysis, the selected model showed adequate a posteriori predictive performance. Bias and imprecision were lowest in the presence of two prior measurements. Additionally, this model showed to be useful in a limited sampling strategy as it adequately predicted total posaconazole exposure from one (non-)trough concentration. CONCLUSION: We validated an MIPD strategy for posaconazole for its fit-for-purpose. Thereby, this study is an important first step towards MIPD-supported posaconazole dosage optimization with the goal to improve antifungal treatment in clinical practice.

Population Pharmacokinetics of Total and Unbound Isavuconazole in Critically Ill Patients: Implications for Adaptive Dosing Strategies.

BACKGROUND AND OBJECTIVES: Isavuconazole is a broad-spectrum antifungal agent for the management of invasive fungal disease. Optimised drug exposure is critical for patient outcomes, specifically in the critically ill population. Solid information on isavuconazole pharmacokinetics including protein binding in patients in the intensive care unit is scarce. We aimed to describe the total and unbound isavuconazole pharmacokinetics and subsequently propose a dosage optimisation strategy. METHODS: A prospective multi-centre study in adult intensive care unit patients receiving isavuconazole was performed. Blood samples were collected on eight timepoints over one dosing interval between days 3-7 of treatment and optionally on one timepoint after discontinuation. Total and unbound isavuconazole pharmacokinetics were analysed by means of population pharmacokinetic modelling using NONMEM. The final model was used to perform simulations to assess exposure described by the area under the concentration-time curve and propose an adaptive dosing approach. RESULTS: Population pharmacokinetics of total and unbound isavuconazole were best described by an allometrically scaled two-compartment model with a saturable protein-binding model and interindividual variability on clearance and the maximum binding capacity. The median (range) isavuconazole unbound fraction was 1.65% (0.83-3.25%). After standard dosing, only 35.8% of simulated patients reached a total isavuconazole area under the concentration-time curve > 60 mg·h/L at day 14. The proposed adaptive dosing strategy resulted in an increase to 62.3% of patients at adequate steady-state exposure. CONCLUSIONS: In critically ill patients, total isavuconazole exposure is reduced and protein binding is highly variable. We proposed an adaptive dosing approach to enhance early treatment optimisation in this high-risk population. CLINICAL TRIAL REGISTRATION: ClinicalTrials.gov identifier: NCT04777058.

High Variability in Isavuconazole Unbound Fraction in Clinical Practice: A Call to Reconsider Pharmacokinetic/Pharmacodynamic Targets and Breakpoints.

Isavuconazole exposure-response relationships have been studied with a focus on total rather than unbound exposure, assuming a constant unbound fraction of 1%. We observed a median (range) unbound fraction of 1.59% (0.42-5.30%) in patients. This highly variable protein binding asks for re-evaluation of current pharmacokinetic and pharmacodynamic targets for isavuconazole.

Repurposing antifungals: population pharmacokinetics of itraconazole and hydroxy-itraconazole following administration of a nanocrystal formulation.

OBJECTIVES: To describe itraconazole and hydroxy-itraconazole pharmacokinetics following intravenous (IV) administration of a previously developed nanocrystal formulation (NCF) in haematopoietic cell transplant (HCT) recipients for prophylaxis of invasive fungal disease. METHODS: In a prospective Phase II study, 10 HCT recipients received itraconazole NCF administered in 2-hour infusions of 200 mg twice daily for 2 days, followed by 200 mg once daily until Day 14. Full pharmacokinetic curves were obtained on Days 7 and 14. Additional samples were collected pre- and post-infusion until Day 6, pre-infusion on Days 10 and 12, and during washout on Days 16, 17, 18, 19 and 28. Itraconazole and hydroxy-itraconazole pharmacokinetics were analysed by non-linear mixed-effects population pharmacokinetic modelling. RESULTS: Four-hundred and seventy-one itraconazole and 471 paired hydroxy-itraconazole concentrations from 10 patients were included for analysis. Data were best described by a semi-mechanistic model with central and peripheral itraconazole compartments and a hydroxy-itraconazole compartment with dissolution of itraconazole drug particles from nanocrystals and first-order distribution and elimination. The final model included interindividual variability on itraconazole clearance and hydroxy-itraconazole clearance. CONCLUSIONS: This study provides information on the pharmacokinetic properties of the itraconazole NCF useful for development of this formulation. Our results suggest that itraconazole NCF is a suitable formulation and may warrant renewal in the setting of repurposing. Our findings may be useful for the reformulation of other highly lipophilic compounds as well.

Posaconazole bioavailability of the solid oral tablet is reduced during severe intestinal mucositis.

OBJECTIVES: This study aimed to describe the absolute oral bioavailability of the solid oral formulation of posaconazole and the impact of severe intestinal mucositis in haematology patients. This study also aimed to describe posaconazole protein binding in haematology patients. METHODS: A pharmacokinetic study was performed of patients receiving induction chemotherapy or a haematopoietic cell transplantation who were randomized to receive 7 days of intravenous posaconazole therapy followed by 9 days of oral therapy, or vice versa. Patients received a posaconazole licensed dose until day 12, after which a reduced once-daily dose of 200 mg was given. At days 7, 12, and 16, blood samples were obtained for pharmacokinetic curves, and trough samples were collected on all other days. Total and unbound posaconazole pharmacokinetics were analyzed by population pharmacokinetic modelling. The presence of severe intestinal mucositis was assessed by plasma citrulline levels and analyzed as a binary covariate using 10 µmol/L as the cut-off. Monte Carlo simulations were performed to simulate posaconazole exposure at a steady state. RESULTS: Twenty-three patients were included for analysis, with 581 total posaconazole concentrations and 91 paired unbound concentrations. Absolute bioavailability in the final model was estimated at 51.4% (percentage relative standard error (%RSE): 56.5) and 67.6% (%RSE: 75.0) in patients with and without severe intestinal mucositis, respectively. Posaconazole unbound fraction was estimated at 2.7% (%RSE: 3.9). DISCUSSION: Posaconazole bioavailability is reduced in haematological patients with severe intestinal mucositis, requiring an increase in oral posaconazole dose to 400 mg twice daily on day 1, followed by 400 mg once daily or a switch to intravenous therapy.

Viral Hepatitis C Therapy: Pharmacokinetic and Pharmacodynamic Considerations: A 2019 Update.

It has been estimated by the World Health Organization (WHO) that over 71 million people were infected with the hepatitis C virus (HCV) in 2015. Since then, a number of highly effective direct-acting antiviral (DAA) regimens have been licensed for the treatment of chronic HCV infection: sofosbuvir/daclatasvir, sofosbuvir/ledipasvir, elbasvir/grazoprevir, sofosbuvir/velpatasvir, glecaprevir/pibrentasvir, and sofosbuvir/velpatasvir/voxilaprevir. With these treatment regimens, almost all chronic HCV-infected patients, even including prior DAA failures, can be treated effectively and safely. It is therefore likely that further development of DAAs will be limited. In this descriptive review we provide an overview of the clinical pharmacokinetic characteristics of currently available DAAs by describing their absorption, distribution, metabolism, and excretion. Potential drug-drug interactions with the DAAs are briefly discussed. Furthermore, we summarize what is known about the pharmacodynamics of the DAAs in terms of efficacy and safety. We briefly discuss the relationship between the pharmacokinetics of the DAAs and efficacy or toxicity in special populations, such as hard to cure patients and patients with liver cirrhosis, liver transplantation, renal impairment, hepatitis B virus or HIV co-infection, bleeding disorders, and children. The aim of this overview is to educate/update prescribers and pharmacists so that they are able to safely and effectively treat HCV-infected patients even in the presence of underlying co-infections or co-morbidities.

Improving antibacterial prescribing safety in the management of COPD exacerbations: systematic review of observational and clinical studies on potential drug interactions associated with frequently prescribed antibacterials among COPD patients.

BACKGROUND: Guidelines advise the use of antibacterials (ABs) in the management of COPD exacerbations. COPD patients often have multiple comorbidities, such as diabetes mellitus and cardiac diseases, leading to polypharmacy. Consequently, drug-drug interactions (DDIs) may frequently occur, and may cause serious adverse events and treatment failure. OBJECTIVES: (i) To review DDIs related to frequently prescribed ABs among COPD patients from observational and clinical studies. (ii) To improve AB prescribing safety in clinical practice by structuring DDIs according to comorbidities of COPD. METHODS: We conducted a systematic review by searching PubMed and Embase up to 8 February 2018 for clinical trials, cohort and case-control studies reporting DDIs of ABs used for COPD. Study design, subjects, sample size, pharmacological mechanism of DDI and effect of interaction were extracted. We evaluated levels of DDIs and quality of evidence according to established criteria and structured the data by possible comorbidities. RESULTS: In all, 318 articles were eligible for review, describing a wide range of drugs used for comorbidities and their potential DDIs with ABs. DDIs between ABs and co-administered drugs could be subdivided into: (i) co-administered drugs altering the pharmacokinetics of ABs; and (ii) ABs interfering with the pharmacokinetics of co-administered drugs. The DDIs could lead to therapeutic failures or toxicities. CONCLUSIONS: DDIs related to ABs with clinical significance may involve a wide range of indicated drugs to treat comorbidities in COPD. The evidence presented can support (computer-supported) decision-making by health practitioners when prescribing ABs during COPD exacerbations in the case of co-medication.