Posaconazole plasma concentrations in critically ill patients.

BACKGROUND

Posaconazole is an azole antifungal agent with a broad spectrum of activity and a manageable side-effect profile. Although the pharmacokinetics of posaconazole have been described in healthy volunteers who received the drug by means of a nasogastric tube or with nutritional supplements, the pharmacokinetics of posaconazole have not been reported in critically ill patients.

METHODS

Twenty-seven patients in the general intensive care unit managed according to standard protocols were randomly allocated to dose regimens of either 400 mg twice daily or 200 mg 4 times daily. Plasma samples were collected for pharmacokinetic analysis after the first dose and at steady-state. Posaconazole plasma concentrations were compared with suggested effect targets for prophylaxis and treatment.

RESULTS

Mean Cmin steady-state plasma concentrations of posaconazole were low for both regimens (306 and 137 ng/mL for 400 mg twice daily and 200 mg 4 times daily regimens, respectively), as was total exposure to posaconazole in each group [area under the concentration-time curve (AUC0-t) for first dose: 761 and 299 μg·h/L]. Only 17% of patients achieved steady-state Cmin posaconazole plasma concentrations above the suggested target for prophylaxis, and only one patient had a Cmin posaconazole concentration that exceeded the suggested target for treatment effect. Systemic exposure to posaconazole seemed to be subtherapeutic in most patients in this cohort. Poor absorption of posaconazole due to drug interactions may explain the low systemic exposure; however, further investigation is necessary.

CONCLUSIONS

These data suggest that there is a need for an intraveneous formulation of the drug if it is to be used effectively in critically ill patients, and therapeutic drug monitoring is an essential tool in this setting to identify patients with low systemic exposure to prevent therapeutic failure.