Experience using intravenous posaconazole in paediatric and young adult oncology patients

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.

Invasive Mold Infections in Children: Navigating Troubled Waters with a Broken Compass

Incidence of invasive mold infections in children, while rare, is increasing as the population of high-risk patients expands, including premature infants, pediatric patients undergoing treatment for hematological malignancies, or recipients of allogeneic hematologic stem cell transplants. The infectious agents, including Aspergillus spp., Mucorales, and other molds, are especially difficult to treat and have serious morbidity and high mortality. Clinicians must maintain a high index of suspicion for invasive mold infections in at-risk patients. Diagnosis of invasive mold infections is complicated by difficulties isolating pathogens on culture, but progress is being made in immunological and molecular diagnostic technologies. Treatment in children is challenging; no randomized controlled trials exist. There is a growing body of data on treatment, specifically on safer antifungal agents, including indications for treatment, spectrum of coverage, pharmacokinetics for different ages, and pharmacodynamic targets associated with therapeutic success. However, pediatricians must often extrapolate from adult data. In this review, we aim to harmonize the existing body of literature on invasive mold infections in children, covering epidemiology, clinical presentations, diagnostic methods, and principles of management.

Evaluating posaconazole, its pharmacology, efficacy and safety for the prophylaxis and treatment of fungal infections

INTRODUCTION

Invasive fungal diseases (IFDs) are a significant cause of morbidity and mortality among immunocompromised patients. Safe and effective antifungal medications used for prophylaxis and treatment are pivotal in their management. Posaconazole is a promising triazole antifungal agent.

AREAS COVERED

The authors discuss the pharmacological properties of posaconazole, including pharmacokinetics/pharmacodynamics, safety and tolerability profile, together with efficacy data for prophylaxis and treatment as well as its use in special populations based on current literature.

EXPERT OPINION

Posaconazole has a favorable safety and tolerability profile; however, caution is advised when co-administered with agents that are CYP3A4 inhibitors, because their concentration may significantly increase, and their levels should be closely monitored. It has an extended spectrum of activity against yeasts and filamentous fungi. It is successfully used as prophylaxis for patients with acute myeloid leukemia (AML)/myelodysplastic syndrome (MDS) and post-hematopoietic cell transplantation (HCT) with graft-versus-host disease (GVHD). It is the first line treatment for oropharyngeal candidiasis and is also used as a salvage treatment for refractory IFDs. Currently available formulations include the oral suspension, delayed-release tablets and solution for intravenous infusion, all with different PK/PD properties and indications. Its use in children and adolescents is currently being examined in Phase-II clinical trials.

A Population Pharmacokinetic Modeling and Simulation Study of Posaconazole Oral Suspension in Immunocompromised Pediatric Patients: A Short Communication

BACKGROUND

Posaconazole oral suspension emerged as a promising candidate for prophylaxis of invasive fungal infections in immunocompromised children. Its pharmacodynamic advantages include a broad-spectrum activity and a favorable safety profile; however, they are overshadowed by its large pharmacokinetic (PK) variability, which might cause subtherapeutic exposure. The aim of this study was to develop a population (pop) PK model based on rich sampling data to better understand the PK of posaconazole oral suspension in pediatric patients.

METHODS

Data were obtained from a prospective interventional study involving hospitalized pediatric patients with a hematologic malignancy and prophylactically treated with posaconazole oral suspension. After constructing the popPK model, the probability of target attainment (PTA; 100% T ≥ 0.7 mg/L) for prophylaxis under fixed, body weight-based, and body surface area-based dosing was evaluated using Monte Carlo simulation.

RESULTS

Fourteen patients contributed 112 posaconazole plasma concentrations. The PK of posaconazole was adequately described by a 1-compartment model with lag time 2.71 hours [13%]; nonlinear bioavailability ED50 99.1 mg/m2 (fixed); first-order absorption rate constant 0.325 hour-1 [27%]; apparent volume of distribution 1150 L [34%]; and apparent clearance 15.4 L/h [24%] (∼70-kg individual). The bioavailability decreased in the presence of diarrhea and co-treatment with a proton pump inhibitor (PPI). The unexplained interindividual variability in posaconazole PK remained large. The PTA was <85%, irrespective of the simulated dosing strategy. Patients without diarrhea and not administered a PPI had the highest PTA (85% under the fixed 300-mg dosing 4 times per day).

CONCLUSIONS

Therapeutic drug monitoring is recommended during prophylactic posaconazole therapy in immunocompromised pediatric patients. Large-scale comparative studies are needed to characterize the PK variability between different posaconazole formulations in this cohort.

Early experience with remdesivir in SARS-CoV-2 pneumonia

At present, there is no definitive antiviral treatment for coronavirus disease 2019 (COVID-19). We describe our early experience with remdesivir in four critically ill COVID-19 patients. Patients received a 200 mg loading dose, followed by 100 mg daily intravenously for up to 10 days. All patients had been previously treated with other antivirals before remdesivir initiation. One patient experienced a torsade de pointes requiring cardiac resuscitation and one died due to multiple organ failure. Three patients showed biochemical signs of liver injury. Lymphocyte count increased in all patients soon after remdesivir initiation. Nasal swab SARS-CoV-2 RNA became negative in three of four patients after 3 days of therapy. We observed an in vivo virological effect of remdesivir in four critically ill, COVID-19 patients, coupled with a significant burden of adverse events. Although limited by the low number of subjects studied, our preliminary experience may be relevant for clinicians treating COVID-19.