The present study aims at measuring unbound voriconazole concentrations in plasma and at the relevant target site of systemic fungal infections, i.e. the interstitial space fluid of soft tissues, to assess the target site pharmacokinetics. For this purpose the microdialysis technique will be employed which is capable of measuring the unbound, microbiologically active concentration of antifungals in the interstitial space fluid of virtually all tissues. This is the first human study of this drug employing the microdialysis technique determining the target site concentrations over several days (single and multiple dosing).