Thrombolytic medicines, such as streptokinase, urokinase, or tissue-type plasminogen activator (t-PA), interfere with the action of thrombin, which is needed to form blood clots. These medicines help to dissolve blood clots and may be used to treat pulmonary embolism in life-threatening situations.

Research continues on the best use of thrombolytics to treat pulmonary embolism. All thrombolytics can cause serious bleeding. Bleeding inside the brain is a particular danger that can cause a stroke or death. In general, thrombolytics are used only where the risk of bleeding can be balanced against the risks of not dissolving the blood clot rapidly. This usually occurs when a person has a large blood clot that is:¹

• Severely blocking blood flow.
• Decreasing the heart's ability to pump blood.
• Causing very low blood pressure and shock.

These medicines are given through a vein in the hand or arm. Occasionally it is necessary to insert a catheter and give the medicine directly into the pulmonary artery. A person must be hospitalized to receive thrombolytic medicines.