Intermittent Dosing of Micafungin Is Effective for Treatment of Experimental Disseminated Candidiasis in Persistently Neutropenic Rabbits

Background. The current standard of treatment of invasive candidiasis with echinocandins requires once-daily therapy. To improve quality of life, reduce costs, and improve outcome, we studied the pharmacokinetics (PK), efficacy, and safety of alternate dosing regimens of micafungin (MFG) for the treatment of experimental subacute disseminated candidiasis. Methods. MFG was administered for 12 days starting 24 hours after intravenous inoculation of 1 × 10³ Candida albicans blastoconidia. Study groups consisted of MFG at 1 mg/kg every 24 hours (MFG1), 2 mg/kg every 48 hours (MFG2), and 3 mg/kg every 72 hours (MFG3), and untreated controls. PK of MFG were determined on day 7 by high-performance liquid chromatography and modeled using nonparametric adaptive grid program. A 2-compartment PK model with volume of the central compartment (V_c), clearance (SCL), and the intercompartmental rate constants K_cp and K_pc was used. The fungal burden in 7 tissues was determined 312 hours after the initiation of therapy. Results. PK of MFG were linear and the parameter means ± SD were V_c= 0.41 ± 0.18 L, K_cp= 2.80 ± 1.55/hour, K_pc= 1.71 ± 0.93/hour, and SCL= 0.16 ± 0.003 L/hour (r²= 0.99). The area under the plasma drug concentration - time curve for MFG1, MFG2, and MFG3 was 198.7 ± 19.8, 166.3 ± 36.7, and 192.8 ± 46.2 mg × hour/L, respectively (P=. 24). All treatment groups showed significant and comparable resolution of (1→3)-β-D-glucan levels and clearance of C. albicans from liver, spleen, kidney, brain, lung, vitreous humor, and vena cava in comparison to untreated controls (P ≤. 05). There were no differences in hepatic or renal function among study groups. Conclusions. Less fractionated MFG regimens of every 48 and 72 hours are safe and as effective in experimental disseminated candidiasis as once-daily therapy in neutropenic hosts.