Factors determining the therapeutic window for stroke.

The duration of the window to treat acute cerebral ischemia has become an important question since the first effective drug for stroke victims has become available. Statistical analysis of relevant animal studies suggests that irreversible focal injury begins within a few minutes and is complete within about 6 hours. There will be substantial difficulties in attempting to obtain accurate estimates of the duration of ischemia that causes permanent damage in patients unless technical obstacles are overcome. Empirical estimates of the therapeutic window for stroke can be obtained from properly designed clinical trials, but optimal care will continue to necessitate urgent treatment.