Inclusion criteria:

1. Age 18-80.

2. Spontaneous SAH confirmed by head CT.

3. Saccular brain aneurysm is identified and treated, either surgically or endovascularly.

4. SAH Fisher grade >1 or modified Fisher grade >0.

5. EVD placed for acute hydrocephalus, or LD placed for draining bloody CSF as deemed necessary by the treating physician.

6. Any clinical scenario leading to the diagnosis of possible vasospasm, which includes:

   1. Mean flow velocity of MCA >120, or Lindegaard Ratio ( LR ) > 3.
   2. Any intracranial artery including MCA, ACA, PCA, and BA, TCD showed an upward trend of mean flow velocity for 2 consecutive days (>25cm/s/day).
   3. Clinical deterioration including mental status change (GCS score decrease > 2) and focal neurological deficit unable to be attributed to other known neurological reasons.
   4. Evidence of vasospasm on CTA or DSA, or ischemic change by CTP, MRI.

7. Within 14 days of onset of SAH.

8. Informed consent obtained from the patient or family member.

Exclusion criteria:

1. Hunt-Hess Grade 5 or WFNS Grade 5 (no clinical improvement after EVD placement for acute hydrocephalus).
2. Bacterial or distal aneurysms without subarachnoid hemorrhage in the basal cisterns.
3. The treating physician determines that the culprit aneurysm has not been fully repaired, with a very high likelihood of rebleeding in the near term.
4. History of head trauma within the past 3 months.
5. Any recent brain disease within 3 months, such as tumors, stroke, epilepsy, vasculitis, arteriovenous malformation, hydrocephalus, etc.
6. History of psychiatric disorders or seizures within 3 months.
7. Severe concurrent medical conditions.
8. Pregnant women or those of childbearing potential with a positive urine or serum β-human chorionic gonadotropin (HCG) test.
9. Lactating women.
10. Life expectancy of less than 1 year prior to aSAH onset.
11. Pre-morbid mRS score >1.
12. Participation in another randomized clinical trial that may confound the evaluation of this study.

History of severe allergic reactions to study medication Currently pregnant or breastfeeding Recent participation in another clinical trial within the last 30 days Presence of uncontrolled medical conditions that could affect safety