A Trial Comparing Efficacy and Safety of Voriconazole Administered With Therapeutic Drug Monitoring vs. Standard Dosing

Inclusion Criteria: * Indication for voriconazole administration: proven, probable, or possible IMI, excluding zygomycosis (based on the revised EORTC/MSG consensus definitions) \[De Pauw, Clin Infect Dis. 2008; 46:1813\]. * Male or female ≥12 years of age. * Evidence of a personally signed and dated informed consent document in accordance with local regulatory and legal requirements indicating that the subject (or a legally acceptable representative) has been informed of all pertinent aspects of the study. * Subjects who are willing and able to comply with scheduled visits, treatment plan, laboratory tests, and other study procedures. Exclusion Criteria: * Known history of allergy, hypersensitivity or serious reaction to azole antifungals. * Patients with aspergilloma or allergic bronchopulmonary aspergillosis (ABPA). * Patients with chronic invasive aspergillosis with duration of symptoms or radiological finding for more than 4 weeks prior to study entry. * Patients who are receiving and cannot discontinue the following drugs at least 24 hours prior to randomization: terfenadine, pimozide or quinidine (because of the possibility of QT prolongation), St John's wort preparation. * Patients receiving any of the following medications: sirolimus, rifampin, rifabutin, carbamazepine, long acting barbiturates (e.g., phenobarbital, mephobarbital), ritonavir, efavirenz, or ergot alkaloids (e.g., ergotamine, dihydroergotamine). * Receipt of more than 5 days of voriconazole as treatment prior to enrollment. * Receipt of 7 days or more of systemic antifungal treatment for the current episode of IMI. * Severe liver dysfunction (defined as total bilirubin, AST, ALT, or alkaline phosphatase \>5x upper limit of normal). Local laboratory results may be used to qualify individuals for enrollment. * Patients with any condition which, in the opinion of the investigator, could affect patient safety, preclude evaluation of response, or make it unlikely that the proposed course of therapy can be completed. * Patients who have already participated in this trial within the last 30 days. * Patients with a high likelihood of death due to factors unrelated to IA (e.g., due to relapsed malignancy, severe GVHD, other underlying diseases, etc.) within 30 days following planned enrollment (investigator's discretion). * Patients that weigh \<45 and \>120 kg, respectively, upon enrollment. If patients' weight is beyond those limits upon serial assessments during the study period, the study monitor should be contacted and decisions to keep or withdraw subject from the study will be made.