Intensive Blood Pressure Reduction in Acute Cerebral Haemorrhage Trial (INTERACT)

Around 17 million people suffer stroke each year and of the 11 million survivors, at least one third will remain dependent on others for direct personal care or supervision in their everyday activities. The most lethal of all stroke subtypes is intracerebral haemorrhage, which kills or disables most of those it strikes.

A flagship program of research at The George Institute concerns the treatment of patients suffering this type of stroke. The focus of the INTERACT study is the effects of immediately lowering the blood pressure of people admitted to hospital with an intracerebral haemorrhage. Previous George Institute studies have shown that long term blood pressure lowering after stroke is a very effective way to reduce stroke recurrence, but there is no clear evidence as to whether lowering blood pressure in hospital immediately after the onset of a stroke provides similar benefit.

Preliminary results from the INTERACT pilot study suggested that rapid blood pressure lowering after intracerebral haemorrhage reduced the amount of intracerebral bleeding, which may have beneficial effects on survival and disability. This is now being tested in the main INTERACT study among 3000 patients with intracerebral haemorrhage from Australia, New Zealand, China, the USA and Korea.

Despite the magnitude of the burden imposed by this disease, and the high cost to health services, there is no widely available treatment for the condition. However, early rapid blood pressure lowering show considerable promise as a widely applicable, cost-effective therapy that can be readily incorporated into clinical practice.

Professor Craig Anderson
Neurological and Mental Health Divsion
The George Institute, Australia

Results from the pilot study were published in Lancet Neurology. Results from the main study should be available in 2012.


INTERACT aims to determine if early and intensive blood pressure lowering therapy can reduce death and disability from brain haemorrhage.


The study is an open, blinded-endpoint, randomised controlled trial that is being conducted in Australia, New Zealand, China, the USA and Korea.

Three thousand participants within six hours of acute brain haemorrhage onset are required for the main study. Participants will be randomised to either early intensive blood pressure lowering, or blood pressure management according to current American Heart Association guidelines. We will follow-up with study participants for three months.

Before the main study is conducted, a vanguard phase, involving 400 patients from 60 clinical centers in Australia, New Zealand, China, the USA and Korea is currently underway to obtain epidemiological and feasibility data. The primary outcomes of the pilot study are to:

  • Define recruitment rates
  • Confirm that blood pressure reduction is possible
  • Establish haematoma expansion rates at zero to six hours
  • Quantify outcome event rates
  • Show safety
  • Characterise background care
  • Evaluate adherence to follow-up