Dementia-Like Symptoms Associated With Posaconazole

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.

Scedosporiosis and lomentosporiosis: modern perspectives on these difficult-to-treat rare mold infections

SUMMARYAlthough Scedosporium species and Lomentospora prolificans are uncommon causes of invasive fungal diseases (IFDs), these infections are associated with high mortality and are costly to treat with a limited armamentarium of antifungal drugs. In light of recent advances, including in the area of new antifungals, the present review provides a timely and updated overview of these IFDs, with a focus on the taxonomy, clinical epidemiology, pathogenesis and host immune response, disease manifestations, diagnosis, antifungal susceptibility, and treatment. An expansion of hosts at risk for these difficult-to-treat infections has emerged over the last two decades given the increased use of, and broader population treated with, immunomodulatory and targeted molecular agents as well as wider adoption of antifungal prophylaxis. Clinical presentations differ not only between genera but also across the different Scedosporium species. L. prolificans is intrinsically resistant to most currently available antifungal agents, and the prognosis of immunocompromised patients with lomentosporiosis is poor. Development of, and improved access to, diagnostic modalities for early detection of these rare mold infections is paramount for timely targeted antifungal therapy and surgery if indicated. New antifungal agents (e.g., olorofim, fosmanogepix) with novel mechanisms of action and less cross-resistance to existing classes, availability of formulations for oral administration, and fewer drug-drug interactions are now in late-stage clinical trials, and soon, could extend options to treat scedosporiosis/lomentosporiosis. Much work remains to increase our understanding of these infections, especially in the pediatric setting. Knowledge gaps for future research are highlighted in the review.