− if you have high blood pressure; − if you have problems with circulation of blood in the brain (cerebrovascular disease); − if you have had gastrointestinal (gut) or genitourinary bleeding within the last ten days (this may cause blood in stools or urine); − if you have a heart valve abnormality (e. g. mitral stenosis) with an abnormal heart rhythm (e. g. atrial fibrillation); − if you have had an intramuscular injection in the last two days; − if you are aged over 75 years; − if you weigh less than 60 kg.