Association of adverse effects with high serum posaconazole concentrations

Correction of posaconazole concentrations for hypoalbuminemia

BACKGROUND

Posaconazole is an example of a highly protein-bound drug (>98%) in which therapeutic drug monitoring (TDM) is commonplace. Total drug concentration is typically measured, and in the setting of hypoalbuminemia, total concentrations are lower despite no anticipated change in unbound concentration. Data support that unbound posaconazole concentration is responsible for antifungal activity and, in theory, is responsible for adverse effects that are dose-related. However, the therapeutic range of posaconazole is expressed as total concentration. The objective of this study was to investigate the use of an equation to correct posaconazole concentrations for albumin concentration as a surrogate for measurement of unbound concentration.

METHODS

Data on unbound and total posaconazole concentration were acquired retrospectively from a study of posaconazole pharmacokinetics in critically ill patients. The relationship between total and unbound concentration was explored with and without albumin as a covariate using linear regression. Correction equations were used to normalize total concentration to an albumin concentration of 4.4 g/dL.

RESULTS

A total of 78 pairs of total and unbound concentrations were available. Total and unbound posaconazole concentrations were determined using ultra-high-performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS). The median fraction unbound was 0.00645 (interquartile range of 0.00331-0.00794). Albumin concentration plays a highly significant role in the interpretation of TDM results. In a patient with hypoalbuminemia, a corrected concentration (Ccorr) = Ct/(0.01 + 0.99·Alb/4.4), where Ct is the total concentration and Alb is the albumin concentration in units of g/dL, is suggested. This equation can be further simplified to Csim = Ct·4.4/Alb, where Csim is a close approximation of Ccorr.

CONCLUSIONS

Hypoalbuminemia is associated with lower total concentrations of posaconazole; however, the "active" unbound concentration is not expected to systematically change. As a result, total posaconazole concentrations in the therapeutic range for patients with hypoalbuminemia are more likely to be associated with toxicity, especially when doses are increased to achieve "therapeutic" concentrations.

Effectiveness of combined proton pump inhibitors and posaconazole prophylaxis against invasive fungal infections in patients with hematologic malignancies: a retrospective study

BACKGROUND

Posaconazole is widely recommended for preventing and treating invasive fungal infections (IFIs) in immunocompromised patients, especially those with prolonged neutropenia. However, the concentration of the oral suspension formulation can be affected by factors such as co-administration with acid-suppressing medications, influencing its efficacy and safety.

AIM

This study examined the impact of proton pump inhibitors (PPIs) and other factors on posaconazole concentrations and the concentration-to-dose ratio (C/D) while also evaluating adverse drug reactions in patients with hematologic malignancies.

METHOD

We conducted a retrospective analysis of patients who received posaconazole for IFI prophylaxis or treatment, assessing demographic and clinical data, adverse reactions, treatment outcomes, and drug concentration assays. The study focused on the effects of PPIs on Cmin and C/D.

RESULTS

Data from 283 posaconazole Cmin measurements in 86 patients were analyzed. The incidence of probable or proven IFIs was 6.4% (5/78). PPI use reduced posaconazole Cmin levels but did not significantly impact prophylactic efficacy. Esomeprazole and rabeprazole were explicitly associated with decreased Cmin. Hepatotoxicity was linked to the co-administration of hepatotoxic drugs, indicating that posaconazole was not the sole contributor.

CONCLUSION

Co-administration of esomeprazole or rabeprazole lowers posaconazole plasma concentrations without compromising prophylactic efficacy against IFIs. Nonetheless, caution is advised when combining these drugs in high-risk immunocompromised patients.

Therapeutic drug monitoring of azole antifungal agents

Deep-seated mycoses are generally opportunistic infections that are difficult to diagnose and treat. They are expected to increase with the spread of advanced medical care and aging populations, thus highlighting the need for safe, effective, and rapid drug-based treatments. Depending on a patient's age, sex, underlying diseases, and immune system status, therapeutic drug monitoring (TDM) may be important for assessing variable pharmacokinetic parameters, as well as preventing drug-drug interactions, adverse events, and breakthrough infections caused by fungal resistance. Azole antifungal agents play an important role in the prevention and treatment of deep-seated fungal infections, with each azoles having its own unique pharmacokinetic properties and specific adverse events. Therefore, it is necessary to use national and international guidelines to build evidence for the expansion of TDM indications. This review focuses on the clinical utility and future perspectives of TDM using azole antifungal agents, in the context of recent evidence in the literature.

Approaches for posaconazole therapeutic drug monitoring and their clinical benefits

OBJECTIVE

This review examines the progress of research on posaconazole therapeutic drug monitoring (TDM) that has focused on differences in the TDM of posaconazole after clinical application in different formulations and in different populations, the factors that affect posaconazole concentrations, the advantages of posaconazole TDM in terms of clinical efficacy and cost savings, and measurement methods.

METHODS

A literature search (2006 to 2024) was performed in PubMed and Embase with the following search terms: noxafil, posaconazole hydrate, posaconazole, drug monitoring, therapeutic drug monitoring, and TDM. Abstracts of review articles, prospective studies, and retrospective studies were reviewed.

RESULTS

TDM should be implemented earlier for posaconazole tablets and injections than for oral posaconazole suspensions. Posaconazole TDM is beneficial for improving clinical efficacy, and the incidence of breakthrough invasive fungal infections (IFIs) can be significantly reduced by gradually adjusting the posaconazole dose in response to TDM in patients with inadequate trough concentrations. Early TDM allows more patients to achieve target therapeutic posaconazole concentrations. TDM can also facilitate dose adjustments, which reduce the cost of this expensive drug. Different assay techniques, including chromatography, microbiological detection, chemofluorimetry, paper spray mass spectrometry, and capillary electrophoresis, can be used for posaconazole TDM.

CONCLUSIONS

Posaconazole TDM has potential clinical utility and cost-saving benefits and could improve the outcomes of IFI treatment.

Posaconazole in paediatric malignancy and haematopoietic stem cell transplant: dosing to achieve therapeutic concentration

OBJECTIVES

Posaconazole is increasingly used for the treatment and prophylaxis of invasive fungal infections in immunocompromised children. We aimed to review evidence for paediatric posaconazole dosing regimens focusing on attainment of target concentrations and frequency of adverse effects.

METHODS

In May 2023, the Cochrane, Embase, MEDLINE and PubMed databases were searched for articles reporting posaconazole dosing in children with malignancy or post-haematopoietic stem cell transplantation. Studies reporting the attainment of target serum concentrations were included.

RESULTS

Overall, 24 studies were included. Eighteen studies of the oral suspension consistently reported poor attainment of target concentrations for prophylaxis (≥0.7 µg/mL, 12%-78%) despite high daily doses of 14-23 mg/kg/day (max. 1200 mg/day). Target attainment was significantly affected by gastric pH and food intake. Six studies of the delayed-release tablet (DRT) reported 58%-94% achieved concentrations ≥0.7 µg/mL, with the majority using lower doses of 4-12 mg/kg/day (max. 300 mg/day). Similarly, one study of powder for oral suspension found 67%-100% achieved target concentrations with a dose of 6 mg/kg/day (max. 300 mg/day). As expected, the IV formulation had high attainment of prophylaxis targets (81%-90%) with 6-10 mg/kg/day (max. 400 mg/day). All formulations were well tolerated, and no relationship between adverse effects and posaconazole concentrations was identified.

CONCLUSIONS

The required posaconazole dose in immunocompromised children varies depending on the formulation. The IV infusion had the highest attainment of therapeutic concentration followed by the DRT and powder for suspension. By contrast, the oral suspension had low attainment of target concentrations despite higher daily doses.

Therapeutic drug monitoring of antifungal therapies: do we really need it and what are the best practices?

INTRODUCTION

Despite advancements, invasive fungal infections (IFI) still carry high mortality rates, often exceeding 30%. The challenges in diagnosis, coupled with limited effective antifungal options, make managing IFIs complex. Antifungal drugs are essential for IFI management, but their efficacy can be diminished by drug-drug interactions and pharmacokinetic variability. Therapeutic Drug Monitoring (TDM), especially in the context of triazole use, has emerged as a valuable strategy to optimize antifungal therapy.

AREAS COVERED

This review provides current evidence regarding the potential benefits of TDM in IFI management. It discusses how TDM can enhance treatment response, safety, and address altered pharmacokinetics in specific patient populations.

EXPERT OPINION

TDM plays a crucial role in achieving optimal therapeutic outcomes in IFI management, particularly for certain antifungal agents. Preclinical studies consistently show a link between therapeutic drug levels and antifungal efficacy. However, clinical research in mycology faces challenges due to patient heterogeneity and the diversity of fungal infections. TDM's potential advantages in guiding Echinocandin therapy for critically ill patients warrant further investigation. Additionally, for drugs like Posaconazole, assessing whether serum levels or alternative markers like saliva offer the best measure of efficacy is an intriguing question.