Cathlyse 18 Injection 1's should not be used if you are allergic to any of the components in Cathlyse 18 Injection 1's, in patients with active internal bleeding, recent stroke, recent intracranial or intraspinal surgery or serious head trauma, intracranial neoplasm (brain tumour), arteriovenous malformation, or aneurysm (ballooning and weakened area in an artery), known bleeding diathesis (tendency to bleed or bruise easily), or severe uncontrolled hypertension. Cathlyse 18 Injection 1's may cause bleeding, hypersensitivity reactions, or cholesterol embolism. Inform your doctor if you have/had recent major surgery, cerebrovascular disease, recent gastrointestinal/genitourinary bleeding, hypertension, subacute bacterial endocarditis, severe hepatic or renal disease, if you are over 75 years or if you are taking any oral anticoagulants. Consult your doctor if you are pregnant or breastfeeding. The safety and effectiveness of Cathlyse 18 Injection 1's in children have not been established.