Subdural hematoma (SDH) is a common condition experienced after head injury. Blood collects on the surface of the brain, causing headaches which can progress to confusion, weakness, or even coma. While patients with SDH often receive surgery, not all patients require surgery right away to ease pressure on the brain. After surgery, there can be up to 30 percent chance of more bleeding and the need for more surgeries. Given this, a drug capable of lowering the chance of more bleeding and speeding the recovery of the patient is highly desirable. In this study, we will test a commonly used, cheap drug called Tranexamic Acid (TXA). While the body stops unwanted and sometimes dangerous bleeding naturally by forming blood clots, TXA stops these blood clots from breaking down, which helps to keep bleeding spots plugged. Our previous study showed that TXA helped speed up patients' recovery; but a larger number of patients is necessary to evaluate how well TXA works to reduce bleeding and improve patient-reported outcomes. In this study, regardless of the need for surgery, half of the patients will be randomly assigned to take TXA, while the other half will take a placebo, which is a look-alike substance that contains no active drug. We will measure multiple outcomes over time to determine if TXA is working and lowers healthcare and personal costs, while also taking blood and surgical samples, to better understand how this drug works in SDH patients.

Inclusion Criteria:

• Patients aged 45 and older weighing between 45-150 kg diagnosed with symptomatic SDH will be included. SDH is defined as unilateral or bilateral crescentic collection of blood (hyper, iso, or hypodense, or mixed density) of greater than or equals to 8 mm in thickness along the cerebral convexity on CT of the head. Symptomatic SDH patients eligible for inclusion are those with SDH with one or more of the following symptoms attributable to the SDH: headache, gait disturbance, confusion or cognitive decline, limb weakness or numbness/paresthesia, speech or visual disturbance, drowsiness or impaired consciousness, seizures, impaired cognition, or memory loss at the time of assessment.

Exclusion Criteria:

- Patients will be excluded for any of the following conditions:

1. Asymptomatic for longer than 72 hours
2. SDH less than 8 mm in maximal thickness
3. Have an acutely deteriorating neurological status (e.g., brain herniation with pupillary dilation, aneurysm rupture, etc.) that is likely to be fatal within 6 hours or less due to a predominantly acute SDH
4. Presence of brain contusion larger than 5 cubic centimeters or subarachnoid hemorrhage (SAH) thicker than 10 mm with Glasgow Coma Scale (GCS)< 13
5. Patients with primarily interhemispheric or tentorial SDH
6. Hypersensitivity to TXA or any of the placebo ingredients
7. Pregnancy
8. Irregular menstrual bleeding with unidentified cause
9. Known acquired colour vision disturbances
10. Hematuria caused by renal parenchymal disease
11. Acute and chronic renal insufficiency indicated by estimated Glomerular Filtration Rate (eGFR) ≤ 30 mL/min
12. Concomitant intake of birth control pill and/or hormonal replacement therapy, and anti-inhibitor coagulant concentrates (factor VIII inhibitor bypass activity (FEIBA), factor VII, activated factor IX)
13. Consumption coagulopathy/disseminated intravascular coagulation (DIC) in the last 7 days
14. Not competent to take study medication properly and regularly or not having access to caregiver that is able to comply with study medication administration
15. Mechanical heart valve
16. Liver cirrhosis
17. Recent venous and/or arterial thromboembolism within 6 months of study enrolment
18. SDH caused by intracranial hypotension
19. Known thrombophilia (e.g., antiphospholipid syndrome)
20. Any active malignancy: metastatic cancer systemically or to the brain or a primary malignant brain tumour treated within the last 6 months
21. Previous enrolment in this trial for a prior episode
22. Time interval >3 days from the time of clinical assessment to eligibility assessment
23. Patients weighing <45 kg or >150 kg
24. Patients received any amount of TXA upon admittance to hospital prior to enrolment

Research Assistant Research Coordinator