Estimates of neuronal loss in acute ischemic stroke show that the typical patient may lose 1·9 million neurons each minute that treatment is delayed. Consequently, significant emphasis has been placed on early evaluation and thrombolysis with tissue plasminogen activator (TPA), the only approved thrombolytic therapy. TPA should be administered as a bolus followed by an immediate infusion because of its short half life. However, in the real life clinical situation, delays in starting the infusion after the bolus can occur. Similarly, once infusion has started, interruptions in the infusion of TPA can also occur. These scenarios may result in lower serum concentrations which could decrease the effectiveness of thrombolysis. We sought to simulate, the influence of bolus infusion delays and also the influence of different intervals of interruptions in the infusion of TPA on serum TPA concentrations.