By AMY ADAMS

After a stroke, a person typically has just three hours to reach a hospital and receive the one drug approved to help save threatened brain cells.

This narrow treatment window limits the drug’s usefulness to less than one-quarter of all stroke patients who squeak in under the deadline. A new study published in the March 6 issue of The Lancet suggests this treatment window may remain open longer, but also highlights the importance of getting treated as quickly as possible.

“The sooner you treat the patient the better the chance that they will have a good recovery from the stroke,” said Gregory Albers, MD, professor of neurology and neurological sciences and director of the Stanford Stroke Center. Albers was one of the main authors of the report.

Albers said this study sends two messages to doctors who treat stroke patients. The first is that patients should receive a clot-busting drug called tPA as soon as possible after arriving at the hospital.

“In routine clinical practice it is common for patients to be treated right at the end of the three-hour limit, even if they arrived at the hospital within an hour of the stroke,” Albers said. The study recommends that all hospitals try to administer tPA treatment within an hour of a stroke patient’s arrival.

The second message is that tPA appears to be effective even after the three-hour time period passes, though it is less effective than when given earlier.

This study combined data from six previous studies looking at tPA’s effectiveness compared to a placebo. Two studies included patients who received tPA up to three hours after the stroke, and the other four studies went out to five or six hours. Taken on their own, the five- to six-hour trials didn’t find any convincing benefit to giving tPA after three hours, but none had enough patients to be conclusive. The researchers who led these trials decided to pool individual patient data to take a closer look at the benefit of this therapy.

Altogether, the trials included 2,775 stroke patients who received either tPA or a placebo. Included in this pool were patients from two of the five- to six-hour trials, which are known as the ATLANTIS trials. Albers was on the steering committee that designed, conducted and published the two ATLANTIS trials and he served as the principal representative of these trials for the new publication.

The group looked at how long after the stroke the patients received tPA and how effectively they recovered. Recovery in each study was measured by how well the person could function independently three months after the stroke.

People who received tPA within 90 minutes of their stroke were 2.8 times more likely to recover compared to people who received a placebo. Those who were treated with tPA between 90 to 180 minutes were still doing better than the placebo group three months later, but only by a factor of 1.55 times. Patients treated in the three to four and a half hour window saw the drug’s effectiveness drop to 1.4 times compared to the placebo. After four and a half hours the researchers didn’t see any benefit from administering tPA.

Albers said the question now is what individual patient factors determine how long tPA remains effective. He is leading a National Institutes of Health-sponsored trial designed to see if new MRI techniques can identify which patients are most likely to benefit from tPA after three hours. If successful, this strategy could substantially increase the number of patients who are candidates for this valuable stroke therapy, he said.