Population pharmacokinetics of micafungin over repeated doses in critically ill patients: a need for a loading dose?

OBJECTIVES: To study the population pharmacokinetics of micafungin in critically ill patients, evaluate and optimize dosage regimens. METHODS: An HPLC-fluorescence bioassay for micafungin was developed, fully validated and applied to a pharmacokinetic study conducted in 14 ICU patients. Dense blood sampling was performed from days 1 to 7. A population pharmacokinetic model accounting for interindividual (IIV) and interoccasion variability (IOV) of the PK parameters was developed. Simulations were performed to estimate the probability of target attainment (PTA) for several dosing regimens. KEY FINDINGS: A two-compartment pharmacokinetic model best described the data, with population clearance CL = 1.31 L/h and central volume V1 = 14.2 L. The relatively high IOV observed (45% for CL, 27% for V1) sets limits for the dose individualization in this population. The low PTA on the first day of treatment suggests the need of a loading dose. PTA and CFR estimates show that the current micafungin dosage may be insufficient for the treatment of borderline susceptible Candida strains. CONCLUSIONS: A loading dose of up to 300 mg of micafungin is needed for the treatment of invasive candidiasis in ICU patients while a maintenance dose of up to 200 mg can be considered in empirical antifungal treatment.

[Evaluation of Micafungin Use in Children]. / Çocuklarda Mikafungin Kullaniminin Degerlendirilmesi.

Micafungin is recommended especially in patients with liver and kidney failure and in the presence of other side effects due to antifungals apart from its known priority indications such as invasive candidiasis. The aim of this study was to evaluate the children who have received micafungin treatment. In the study, 125 children who were hospitalized in the pediatric wards and intensive care units of our hospital and had used micafungin between November 2016 and January 2019 were analyzed retrospectively. Clinical data, micafungin indication, blood values on the first and fourth days of the treatment, side effects of the drug and efficacy were evaluated. Sixty percent (75/125) of the patients were male and the mean age of all the patients were 58 ± 67 (0-215, 30) months. Approximately half of the cases (48%) had malignancy and 13% of them were premature. Sixty-two percent (n= 37) of the malignencies were hematological (27 acute lymphocytic leukemia, nine acute myeloid leukemia, one myelodysplastic syndrome) and 38% (n= 23) were oncological (six neuroblastoma, four Hodgkin lymphoma, two Non-Hodgkin's lymphoma, five sarcomas, one hepatoblastoma, five others) malignencies. The major cause of hospitalization was sepsis (53%). The patients had several risk factors like immunosuppressive therapy (n= 68, 54%), neutropenia (n= 61, 49%), central venous catheter (n= 102, 82%), nasogastric tube (n= 63, 50%), endotracheal intubation tube (n= 49, 39%), urinary catheter (n= 14, 11%) and total parenteral nutrition (n= 81, 65%). Thirteen percent (n= 16) of the cases were post-operative patients. Candida species were cultivated in 97 clinical specimens (blood, endotracheal aspirate, sputum, urine, etc.) among 23 (18%) of the patients. Thirteen (10%) of the patients had candidemia and 62% of them were non-albicans strains. In all candidemias, strains were echinocandin susceptible, and blood cultures were negative within four days. When all the patients (n= 125) were evaluated, a significant decrease in C-reactive protein, an increase in sodium, and a decrease in alanine aminotransferase were observed on the fourth day of micafungin treatment (p<0.05). A total of 39 (31%) patients underwent various antifungal treatments for median seven (1-60) days prior to micafungin treatment. Fourteen (36%) of these 39 patients, had elevated liver function tests (LFT), 10 (26%) of them had hypokalemia, and five (13%) of them had elevated renal function tests. Ten (26%) patients had antifungal-induced hypokalemia previously; and potassium levels were normalized after micafungin treatment (p= 0.0001). The patients for which micafungin treatment was chosen due to elevated liver function tests (n= 47, 38%), whether the antifungalinduced or not; alanine aminotransferase and aspartate aminotransferase levels were decreased after micafungin treatment (p= 0.0001 and p= 0.0001, respectively). Nineteen (15%) of the patients have died within the first 30 days of micafungin treatment and one of them had candidemia. No micafungin treatment related significant side effects were observed in any of the patients. Our study showed that micafungin could be a safe and effective option in pediatric cases including newborns with high liver and kidney function tests.

Pharmacokinetics of Micafungin in Critically Ill Patients Receiving Continuous Venovenous Hemodialysis With High Cutoff Membranes.

BACKGROUND: An optimal antifungal therapy for invasive candidiasis in critically ill patients is essential to reduce the high mortality rates. Acute kidney injury is common, and continuous renal replacement therapies are frequently used. Previous studies have demonstrated a lack of effect from different continuous renal replacement techniques on micafungin clearance. However, the use of high cutoff pore size membranes could potentially allow for the loss of albumin and alter micafungin pharmacokinetics. The objective was to explore the pharmacokinetics of micafungin in critically ill patients undergoing continuous venovenous high cutoff membrane hemodialysis (CVVHD-HCO). METHODS: Prospective observational study performed in critically ill patients treated with 100 mg/d of micafungin and undergoing CVVHD-HCO. CVVHD-HCO sessions were performed using Prisma-Flex monitors and dialyzers with a membrane of polyarylethersulfone of 1.1-m surface area and 45-kDa pore size. Blood samples were collected from arterial prefilter, venous postfilter, and the drainage line ports at 0 (predose), 1, 4, 12, 24 hours after dose, and micafungin concentrations were determined using HPLC-UV. RESULTS: Nine patients (55.6% male; age: 28-80 years) were included. Median (range) of micafungin concentrations in the effluent were <0.2 (<0.2-0.4) mg/L at low (predose) and 0.4 (<0.2-0.7) mg/L at high (1 h) concentrations. The extraction ratio was <12% at each time point. A 2-compartment model best described the time course of plasma concentrations, and body weight was the only covariate that improved the model. CONCLUSIONS: This is the first study demonstrating that CVVHD-HCO does not alter the pharmacokinetics of micafungin, and that standard doses of this antifungal can be used.

Exposure-Response Analysis of Micafungin in Neonatal Candidiasis: Pooled Analysis of Two Clinical Trials.

BACKGROUND: Neonatal candidiasis causes significant morbidity and mortality in high risk infants. The micafungin dosage regimen of 10 mg/kg established for the treatment of neonatal candidiasis is based on a laboratory animal model of neonatal hematogenous Candida meningoencephalitis and pharmacokinetic (PK)-pharmacodynamic (PD) bridging studies. However, little is known about the how these PK-PD data translate clinically. METHODS: Micafungin plasma concentrations from infants were used to construct a population PK model using Pmetrics software. Bayesian posterior estimates for infants with invasive candidiasis were used to evaluate the relationship between drug exposure and mycologic response using logistic regression. RESULTS: Sixty-four infants 3-119 days of age were included, of which 29 (45%) infants had invasive candidiasis. A 2-compartment PK model fits the data well. Allometric scaling was applied to clearance and volume normalized to the mean population weight (kg). The mean (standard deviation) estimates for clearance and volume in the central compartment were 0.07 (0.05) L/h/1.8 kg and 0.61 (0.53) L/1.8 kg, respectively. No relationship between average daily area under concentration-time curve or average daily area under concentration-time curve:minimum inhibitory concentration ratio and mycologic response was demonstrated (P > 0.05). Although not statistically significant, mycologic response was numerically higher when area under concentration-time curves were at or above the PD target. CONCLUSIONS: While a significant exposure-response relationship was not found, PK-PD experiments support higher exposures of micafungin in infants with invasive candidiasis. More patients would clarify this relationship; however, low incidence deters the feasibility of these studies.