Assessment of micafungin loading dosage regimens against Candida spp. in ICU patients by Monte Carlo simulations.

OBJECTIVE: To assess the efficacy of loading dose on micafungin by simulating different dosage regimens.

METHODS: A published study of micafungin in ICU patients was employed to simulate nine different dosage regimens which were sorted out three groups in terms of three maintenance doses. Using pharmacokinetic parameters and pharmacodynamic data, 5000-subject Monte Carlo simulations were conducted to simulate concentration-time profiles of micafungin, calculate probabilities of target attainment (PTAs), and cumulative fractions of response (CFRs) in terms of AUC/MIC targets. PTAs were calculated using AUC/MIC cut-offs: 285 (Candida parapsilosis), 3000 (all Candida spp.), and 5000 (non-parapsilosis Candida spp.). PTA or CFR > 90% was considered optimal for a dosage regimen.

RESULTS: The concentration-time profiles of micafungin-simulated dosage regimens were obtained. PTA values were over 90% while applying the loading dose in each group of regimens: for Candida albicans and Candida glabrata (AUC/MIC = 5000), all regimens with loading dose provided PTAs of ≥ 90% for MIC ≤ 0.008 mg/L. The PTAs (AUC/MIC = 3000) were over 90% for MIC ≤ 0.008 mg/L in any regimen. However, for MIC inferior to 0.016 mg/L, only loading dosage regimens provided PTAs exceeding 90%. For C. parapsilosis (AUC/MIC = 285), the maximum MIC of achieving a PTA ≥ 90% was 0.25 mg/L both in the regimens of B (150 mg maintenance dose) and C (200 mg maintenance dose) with loading dose. In addition, CFR of any regimen with loading dose was ≥ 90% against C. albicans and C. glabrata. None of the dosage regimens achieved an expected CFR against C. parapsilosis.

CONCLUSIONS: The dosage regimen of micafungin which had a loading dose of 1.5 times was more suitable for ICU patients infected by Candida spp.