Whole-body physiology-based pharmacokinetics of caspofungin for general patients, intensive care unit patients and hepatic insufficiency patients

Administration and Dosing of Systemic Antifungal Agents in Pediatric Patients

Neonates and immunosuppressed/immunocompromised pediatric patients are at high risk of invasive fungal diseases. Appropriate antifungal selection and optimized dosing are imperative to the successful prevention and treatment of these life-threatening infections. Conventional amphotericin B was the mainstay of antifungal therapy for many decades, but dose-limiting nephrotoxicity and infusion-related adverse events impeded its use. Despite the development of several new antifungal classes and agents in the past 20 years, and their now routine use in at-risk pediatric populations, data to guide the optimal dosing of antifungals in children are limited. This paper reviews the spectra of activity for approved antifungal agents and summarizes the current literature specific to pediatric patients regarding pharmacokinetic/pharmacodynamic data, dosing, and therapeutic drug monitoring.

Simulation of the Pharmacokinetics of Oseltamivir and Its Active Metabolite in Normal Populations and Patients with Hepatic Cirrhosis Using Physiologically Based Pharmacokinetic Modeling

Oseltamivir is a neuraminidase inhibitor widely used to treat and prevent influenza A and B infections, although its safety and pharmacokinetics have not been evaluated in patients with severe hepatic impairment. A physiologically based pharmacokinetic (PBPK) model of the prodrug oseltamivir and its active metabolite, oseltamivir carboxylate (OC), was established and validated to simulate their disposition in adults and predict the exposure in patients with Child-Pugh C cirrhosis (CP-C). The simulated results from PBPK modeling and the observed data after oral administration of various oseltamivir regimens were consistent according to the fold error values of less than 2. Furthermore, the clinical observations published in the literature were comparable with our pharmacokinetic predictions. In patients with CP-C, the oseltamivir C_max was approximately 2-fold increased, and its AUC was approximately 6-fold higher compared with those in normal subjects. In contrast, the AUC of OC in CP-C patients did not differ significantly from that in normal subjects, whereas its C_max was reduced by approximately 30% in the patients. Examination of drug exposure in different health conditions indicated that the oseltamivir exposure was significantly increased in conditions with elevated cirrhosis severity, which might be associated with a higher risk of adverse drug effects, e.g., neuropsychiatric adverse events (NPAEs). In conclusion, the pharmacokinetics of oseltamivir and OC were correctly predicted by PBPK modeling. The model further predicted that the pharmacokinetics of oseltamivir might be altered in liver cirrhosis, depending on the degree of severity.

Dosing of Antimycotic Treatment in Sepsis-Induced Liver Dysfunction by Functional Liver Testing with LiMAx®

Background

Sepsis-treatment is one of the major challenges in our time. Especially fungal infections play an important role in patient's morbidity and mortality. In patients with septic shock, liver function is often significantly impaired and therefore also hepatic drug metabolism is altered.

Case Presentation

We report about a 56-year-old man suffering from invasive fungal infection with multiorgan failure, after complicated medical history due to symptomatic infrarenal aortic aneurysm. On the first postoperative day, a CT scan was undertaken due to massive back pain showing renal infarction on both sides. As qualitative and quantitative renal function was impaired, hemodialysis was started immediately. Subsequently, the patient developed a compartment syndrome of the left leg and underwent fasciotomy. On admission day 7, the patient presented with hematochezia leading to colonoscopy. During this procedure, an ischemic colitis was observed. As conservative treatment failed, the patient underwent Hartmann's procedure due to progredient ischemia followed by a worsening of the clinical status due to sepsis. The patient suffered from an invasive fungal infection with Candida spp. and Aspergillus spp. Systemic antifungal treatment was initiated. Although azoles are considered first-line treatment in these cases we chose the echinocandin caspofungin for its presumed lower impact on liver function compared to azoles like voriconazole or Amphothericin B. However, caspofungin is also metabolised in the liver and can cause hepatotoxic effects. Therefore we measured metabolic liver function capacity using LiMAx®and adapted the patient's dose of caspofungin to the evaluated liver function capacity to achieve an effective and liver-protective level of the active drug. After complicated medical history with 15 weeks of hospital stay, the patient was discharged in general good condition.

Conclusions

To our knowledge, this is the first report that relates antimycotic drug dosing to a functional liver test. We provide a new approach for sepsis treatment considering liver function capacity to optimize dosage of hepatically metabolised drugs with potential hepatotoxic effects.

Pre-Existing Liver Disease and Toxicity of Antifungals

Pre-existing liver disease in patients with invasive fungal infections further complicates their management. Altered pharmacokinetics and tolerance issues of antifungal drugs are important concerns. Adjustment of the dosage of antifungal agents in these cases can be challenging given that current evidence to guide decision-making is limited. This comprehensive review aims to evaluate the existing evidence related to antifungal treatment in individuals with liver dysfunction. This article also provides suggestions for dosage adjustment of antifungal drugs in patients with varying degrees of hepatic impairment, after accounting for established or emerging pharmacokinetic–pharmacodynamic relationships with regard to antifungal drug efficacy in vivo.