COSSACS (Continue or Stop post-Stroke Antihypertensives Collaborative Study): rationale and design

J Hypertens. 2005 Feb;23(2):455-8. doi: 10.1097/00004872-200502000-00029.


Rationale: Up to 40% of acute stroke patients are already taking antihypertensive therapy on hospital admission, and most will develop elevated blood pressure levels as an acute complication of the stroke. However, no clear data exist as to whether antihypertensive therapy should be continued or discontinued in the acute situation. Surveys of clinical practice reveal significant physician variability and no clear guidelines exist.

Objectives: The primary aim of the Continue or Stop post-Stroke Antihypertensives Collaborative Study (COSSACS) is to assess whether existing antihypertensive therapy should be continued or discontinued within the first 24 h for the first 2 weeks following acute ischaemic and haemorrhagic stroke onset.

Design: COSSACS is a multi-centre, prospective, randomized, open, blinded-endpoint study, in which patients on pre-existing antihypertensive therapy, admitted to hospital within 24 h of onset of suspected stroke, and within 36 h of their last dose of antihypertensive medication, are randomized to continue or stop current antihypertensive therapy.

Setting: Acute Stroke Units/ Medical Units of at least 25 UK Teaching and District General Hospitals.

Patients: The study will involve 2900 patients with suspected stroke without specific indication to continue or stop their antihypertensive medication in the opinion of their treating clinician.

Study outcomes: The primary outcome for COSSACS is the proportion of patients who are dead or dependent (defined by a modified Rankin score > 2) at 14 days post-stroke. Secondary outcomes include blood pressure changes, and neurological and functional status at 2 weeks and 6 months post-ictus.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Antihypertensive Agents / therapeutic use*
  • Blood Pressure / drug effects
  • Brain Ischemia / complications
  • Brain Ischemia / diagnosis
  • Brain Ischemia / therapy*
  • Clinical Trials as Topic / standards*
  • Double-Blind Method
  • Multicenter Studies as Topic / standards
  • Outcome and Process Assessment, Health Care*
  • Patient Selection
  • Prospective Studies
  • Recovery of Function
  • Research Design / standards*
  • Stroke / complications
  • Stroke / diagnosis
  • Stroke / therapy*
  • Time Factors
  • United Kingdom


  • Antihypertensive Agents