Management of Drug Interaction between Posaconazole and Sirolimus in Patients Who Undergo Hematopoietic Stem Cell Transplant

Initial sirolimus dosage recommendations for pediatric patients with PIK3CD mutation-related immunodeficiency disease

Sirolimus is used to treat pediatric patients with PIK3CD mutation-related immunodeficiency disease. However, the initial dosages of sirolimus remain undecided. The present study aims to explore initial dosages in pediatric patients with PIK3CD mutation-related immunodeficiency disease. Pediatric patients with this disease were analyzed using the population pharmacokinetic (PPK) model and the Monte Carlo simulation. Body weight and concomitant use of posaconazole were included in the final PPK model, where, under the same weight, clearances of sirolimus were 1 : 0.238 between children without and children with posaconazole. Without posaconazole, the initial dosages of sirolimus were 0.07, 0.06, 0.05, and 0.04 mg/kg/day for body weights of 10–14, 14–25, 25–50, and 50–60 kg, respectively. With posaconazole, the initial dosages of sirolimus were 0.02 mg/kg/day for body weights of 10–60 kg. This is the first attempt to build a sirolimus PPK model for recommending initial dosages in children with PIK3CD mutation-related immunodeficiency disease, thereby providing a reference for individualized clinical drug administration.

Effect of posaconazole on the concentration of intravenous and oral cyclosporine in patients undergoing hematopoietic stem cell transplantation

PURPOSE

This study aimed to investigate the interactions between posaconazole (POS) and intravenously/orally administered cyclosporine A (CsA) in allogeneic hematopoietic stem cell transplant (HSCT) recipients.

METHODS

We included 118 allogeneic HSCT patients who received CsA and POS simultaneously between January 2017 and June 2020 in this study. The ratio of CsA blood concentration (ng/mL) to dosage (mg/day) (C/D) before and after POS initiation was compared.

RESULTS

After the initiation of POS, the level of CsA increased 1 to 2 times in 66% (78/118) of patients compared to those without POS. However, the CsA C/D ratio increased by more than threefold in 6% (7/118) of patients after POS initiation, with an increase of more than fourfold in two patients. The median C/D ratio of CsA increased from 0.89 to 1.23 (P < 0.001) and 0.78 to 1.22 (P < 0.001) after POS initiation when CsA was administered intravenously and orally, respectively. In patients who received POS at the time of transition from intravenous to oral CsA, the value increased from 1.01 to 1.38 (P = 0.001). The route of administration had no significant effect on the change in the CsA C/D ratio (P = 0.615). Additionally, we observed the time required for the C/D ratio to reach a plateau after POS initiation was similar on days 13, 8, and 15 under various scenarios.

CONCLUSION

POS treatment increased blood CsA levels. A large variability was found in the fold-change in the CsA C/D ratio. Therefore, CsA doses should be adjusted by closely monitoring the blood levels of CsA after POS initiation.

Fungal Infections in Lung Transplantation

Purpose of Review

We aim to understand the most common fungal infections associated with the post-lung transplant period, how to diagnose, treat, and prevent them based on the current guidelines published and our center’s experience.

Recent Findings

Different fungi inhabit specific locations. Diagnosis of invasive fungal infections (IFIs) depends on symptoms, radiologic changes, and a positive microbiological or pathology data. There are several molecular tests that have been used for diagnosis. Exposure to fungal prophylaxis can predispose lung transplant recipients to these emerging molds. Understanding and managing medication interactions and drug monitoring are essential in successfully treating IFIs.

Summary

With the increasing rate of lung transplantations being performed, and the challenges posed by the immunosuppressive regimen, understanding the risk and managing the treatment of fungal infections are imperative to the success of a lung transplant recipient. There are many ongoing clinical trials being conducted in hopes of developing novel antifungals.

Clinical Pharmacokinetics of Second-Generation Triazoles for the Treatment of Invasive Aspergillosis and Candidiasis

Second-generation triazoles were developed in response to the quest for more efficacious and safer therapeutic options for the treatment of severe systemic aspergillosis and candidiasis. These agents include voriconazole, posaconazole, isavuconazole, and ravuconazole. The aim of this review was to present and compare the pharmacokinetic characteristics of second-generation triazoles for the treatment of invasive aspergillosis and candidiasis, emphasizing their clinical implications. The MEDLINE, Scopus, EBSCO, Google Scholar, and SCIndeks databases were searched using advanced search options, including the names of second-generation triazoles and pharmacokinetic terms as keywords. The intravenous administration of voriconazole, posaconazole, and isavuconazole results in stable pharmacokinetics of these drugs, with mostly predictable variations influenced by common and usually known factors in routine clinical settings. The high oral bioavailability of isavuconazole and, to some extent, voriconazole makes them suitable for intravenous-to-oral switch strategies. Except for intravenous voriconazole (due to the accumulation of the toxic vehicle hydroxypropyl betadex), dose reduction of second-generation triazoles is not needed in patients with renal failure; patients with hepatic insufficiency require dose reduction only in advanced disease stages. The introduction of therapeutic drug monitoring could aid attempts to optimize the blood concentrations of triazoles and other drugs that are known to or that possibly interact, thus increasing treatment efficacy and safety. There is a need for new studies that are designed to provide useful data on second-generation triazole pharmacokinetics, particularly in special circumstances such as central nervous system and ocular infections, infections in newborns and infants, and in subjects with genetic polymorphisms of metabolizing enzymes.

Drug-drug interactions in patients receiving hematopoietic stem cell transplantation

INTRODUCTION

Recipients of hematopoietic stem cell transplantation (HSCT) are exposed to numerous drugs in both pre- and post-transplantation period, which creates an opportunity for drug-drug interactions (DDIs); if clinically relevant DDIs happen, the risk of adverse treatment outcomes is increased. Areas covered: This review is focused on DDIs in recipients of HSCT that were observed and published as clinical trials, case series or case reports. Relevant publications were found by the systematic search of the following online databases: MEDLINE, SCOPUS, EBSCO, and SCINDEX. Expert opinion: The most important DDIs involve cytostatic or immunosuppressant drug on one side, and antimicrobial drugs on the other. The majority of clinically relevant interactions have pharmacokinetic character, involving drug metabolizing enzymes in the liver. Antifungal azoles inhibit metabolism of many cytostatic and immunosuppressant drugs at cytochromes and increase their plasma concentrations. Macrolide antibiotics and fluoroqunolones should be avoided in HSCT recipients, as they have much larger potential for DDIs than other antibiotic groups. HSCT recipients increasingly receive new immunomodulating drugs, and further observational studies are needed to reveal unsuspected DDIs with clinical relevance.

Effect of isavuconazole on tacrolimus and sirolimus serum concentrations in allogeneic hematopoietic stem cell transplant patients: A drug-drug interaction study

INTRODUCTION

Isavuconazole, a triazole antifungal, is an inhibitor of cytochrome P450 3A4, which also metabolizes tacrolimus and sirolimus. In previous studies, isavuconazole administration increased tacrolimus and sirolimus area under the curve values by 2.3-fold and 1.8-fold, respectively, in healthy adults and tacrolimus concentration/dose (C/D) ratio by 1.3-fold in solid organ transplant patients. We aimed to determine the magnitude of effect of isavuconazole administration on tacrolimus and sirolimus C/D ratios in allogeneic hematopoietic stem cell transplant (alloHSCT) patients.

METHODS

A retrospective, single-center, single-arm study in adult alloHSCT patients who received at least 10 days of combination therapy with isavuconazole and tacrolimus and/or sirolimus as inpatients or outpatients was conducted. Tacrolimus and sirolimus trough serum concentrations were measured up to twice weekly for up to 4 weeks.

RESULTS

Twenty-two patients receiving tacrolimus and twenty patients receiving sirolimus met the inclusion criteria. The mean C/D ratio increased from baseline by 1.42-fold for tacrolimus during week 1 (P = 0.002) and up to 1.56-fold for sirolimus during week 2 (P = 0.02). For the remaining timepoints, tacrolimus and sirolimus C/D ratios were not statistically significantly different from baseline.

CONCLUSION

In alloHSCT patients, modest increases in tacrolimus and sirolimus C/D ratios from baseline were observed within the first 2 weeks after initiation of isavuconazole.

The Hematopoietic Cell Transplant Pharmacist: Roles, Responsibilities, and Recommendations from the ASBMT Pharmacy Special Interest Group

Pharmacists are increasingly recognized as an essential member of the multidisciplinary team for hematopoietic cell transplant (HCT) patients. However, until recently, their educational background, required training, and potential roles have not been well described. Therefore, the purpose of this manuscript is to provide supporting evidence for the HCT Clinical Pharmacist Role Description, which has been endorsed by several organizations including the American Society for Blood and Marrow Transplantation. This document provides justification for the various roles pharmacists fulfill with respect to medication management, transitions of care, patient and provider education, policy development, quality improvement, and research. Furthermore, evidence supporting the value, financially and otherwise, HCT pharmacists provide is reviewed. Pharmacists in the HCT setting are encouraged to report on novel practice models and potential impact of their services to increase awareness and utilization of HCT pharmacists.

Salvage Treatment of Mucormycosis Post-Liver Transplant With Posaconazole During Sirolimus Maintenance Immunosuppression

We describe the first successful case of posaconazole salvage therapy for mucormycosis with concomitant sirolimus (SRL) maintenance immunosuppression following liver transplantation, despite black box drug interaction following intolerance to first-line tacrolimus and amphotericin due to nephrotoxicity and neurotoxicity. This case describes a 55-year-old female who developed rhinocerebral mucormycosis 108 days after liver transplantation. After 3 months of posaconazole therapy, the patient remains free of disease at 3 years posttransplant. This case report illustrates successful resolution of mucormycosis without SRL toxicity to resolve nephrotoxicity of long-term amphotericin on top of already nephrotoxic immunosuppression. With higher bioavailability of recently FDA-approved posaconazole delayed release tablets, this azole may be a therapeutic option for transplant patients who need to remain on CYP3A4-metabolized immunosuppressive agents.

Increased inhibition of cytochrome P450 3A4 with the tablet formulation of posaconazole

Being a substrate of the cytochrome P450 3A4 (CYP3A4) isoenzyme, sirolimus metabolism is decreased when posaconazole is administered concomitantly. However, because of the poor bioavailability of the oral suspension of posaconazole with which low plasma concentrations are obtained, CYP3A4 inhibition is weak and a 50-75% dose reduction of sirolimus is sufficient to avoid sirolimus overdosage. The new tablet formulation allows reaching posaconazole concentrations 3-4 fold higher than those obtained with the oral suspension. Based on a case of sirolimus overdosage following posaconazole tablets administration, we modelled the inhibition of sirolimus clearance by posaconazole, and then simulated several dosage regimens of sirolimus taken together with posaconazole tablets. We were able to describe well the interaction, and found a value of IC50 of posaconazole towards sirolimus clearance of 0.68 μg/mL. The simulations showed that even a 80% decrease of the daily dose of sirolimus is unsuitable in many cases with trough concentrations of posaconazole of 2 μg/mL. A decrease of 40% of the dose with spacing administrations of 3 days may be considered. The clinicians and pharmacologists must be warned that the use of posaconazole tablets may result in an inhibition of CYP3A4 of greater magnitude than with the oral suspension.