1. Objectives:

   • Main objective: To evaluate the efficacy and safety of intrapleural alteplase vs urokinase in patients with complex complicated parapneumonic pleural effusion and empyema.
   • To evaluate the pleural and plasmatic levels of the fibrinolytic system markers after the treatment with alteplase vs urokinase
   • To evaluate the safety of alteplase in the treatment of complex complicated parapneumonic pleural effusion and empyema

2. Design: Multicentric, randomized, parallel, controlled and double blind

3. Main variable: Percentage of curation

4. Study population and number of patients: 204 patients with complex complicated parapneumonic pleural effusions and empyema

5. Duration of the treatment: Three days (main variable), and optional three days (secondary variable)

Inclusion Criteria:

• Empyema and Complex Complicated Parapneumonic Pleural Effusion

Exclusion Criteria:

• Pregnancy or breastfeeding
• Critically illness
• Systemic anticoagulant treatment
• Coagulation Disorder
• Bronchopleural fistula
• Active bleeding
• Recent punction of noncompressive artery
• Stroke in the last 6 months
• Major intervention o major traumatism in the last 6 weeks
• Hypersensibility to urokinase or alteplase
• Severe Liver or kidney failure
• Inclusion in another interventional study in the last month