Inclusion Criteria1. All aneurysmal SAH patients with clinical and or radiological diagnosis.
2. Subjects with age ≥18 years and ≤80 years at the time of screening.
3. The subject or his/ her legal representative is willing to undergo informed consent process prior to enrollment into this study.
4. World Federation of Neurosurgeons scale score ≤ 2
5. Hunt and Hess Stroke scale score ≤ 2
6. Mean velocities of < 200 cm/s in at least 1 vascular axis of the circle of Willis
7. Patients admitted within 4 days of symptom onset.
Exclusion Criteria1. Subject with age < 18 years and >80 years at the time of screening.
2. Time of symptom onset cannot be determined.
3. Subject who is pregnant or lactating.
4. Subjects who have hypersensitivity to acetazolamide, sulfa drugs, or any component of the formulation.
5. Mean velocities of ≥ 200 cm/s in at least 1 vascular axis of the circle of Willis
6. Brain CT or MRI show acute infarction
7. Any acute focal neurological deficit (including any one of these) speech problems, loss of vision, facial or extremity weakness.
8. Hunt and Hess Stroke scale scores > 2
9. World Federation of Neurosurgeons scale scores > 2
10. Subjects with hepatic disease or insufficiency or cirrhosis.
11. Subjects with severe renal disease or dysfunction.
12. Subjects who have decreased sodium and/or potassium levels; hyperchloremic acidosis.
13. Subjects who have adrenocortical insufficiency.
14. The subject or legal representative is unable to provide informed consent.
15. The subject is medically unstable to participate in the trial as determined by the principal investigator.
16. The subject has any end stage medical condition as determined by the principal investigator.