Efficacy and Safety of Activase (Ateplase) vs Placebo in Complicated Pleural Effusions (CPE)/Empyemas

Inclusion Criteria: * Diagnosed with complicated pleural effusions * Ability to provide written informed consent and comply with study assessments for the full duration of the study. * Age \> 18 years Exclusion Criteria * Current use of oral anticoagulants (e.g., warfarin sodium) with an International Normalized Ratio (INR) \>5- Activated partial thromboplastin time (aPPT) \> 80, Platelet count \< 100,000/mm3; * Severe uncontrolled hypertension * Recognized hypersensitivity to Activase; or any component of its formulation; Traumatic pleural effusion * Pregnancy (positive pregnancy test) * In another study for this condition * Any other condition that the investigator believes would pose a significant hazard to the subject if the investigational therapy were initiated * Participation in another simultaneous medical investigation * Recent stroke * Intracranial hemorrhage * arteriovenous malformation or aneurysm * Intracranial neoplasm * Acute myocardial infarction * Acute pulmonary embolus