Optimal timing of thrombolytic therapy in acute ischaemic stroke.

The clinical benefit of thrombolytic therapy for patients experiencing acute cerebral ischaemia has been demonstrated by both clinical trials and phase IV studies. However, such treatments must be initiated in a rapid manner, with treating physicians adhering to strict protocols designed to minimise delays and maximise safety. The efficacy of intravenous drug administration has been established with alteplase (recombinant tissue plasminogen activator; tPA) and ancrod, but only if these drugs can be administered within 3 hours of symptom onset. The use of alteplase beyond this timeframe, or outside of established protocols, may be hazardous. The use of alternative intravenous thrombolytic agents, such as streptokinase, also appears hazardous. Intra-arterial delivery of thrombolytic drugs such as pro-urokinase may extend clinical benefit to the 6-hour time frame.