Safety and Efficacy Study of Alfimeprase in Subjects With Occluded Central Catheters

Inclusion Criteria: * Must give written informed consent * Unable to withdraw 3 mL of blood from a central venous access device * Hemodynamically stable * Available for follow-up assessments Exclusion Criteria: * Inability to infuse at least 2 mL of saline through the catheter * Catheter placed less than 48 hours prior to detection of occlusion * Catheter used for hemodialysis of pheresis * Less than 18 years of age * Evidence of mechanical or nonthrombotic occlusion * Receipt of any thrombolytic agent within 24 hours of randomization * In the opinion of the investigator, subject is at "high risk" for bleeding events of embolic complications, or has a condition for which bleeding constitutes a significant hazard * Increased risk for drug extravasation * Pregnant, lactating, or actively menstruating women and women of child-bearing potential who are not using adequate contraceptive precautions (e.g. intrauterine device, oral contraceptives, barrier methods, or other contraception deemed adequate by the investigator) * Known right-to-left cardiac shunt, patent foramen ovale, or atrial/ventricular septal defect * Participation in any other study of an investigational device, medication, biologic, or other agent within 30 days before enrollment and until the 30-day follow up visit * Any other subject feature that in the opinion of the investigator should preclude study participation