A 52-year-old woman presents with recurrent episodes of severe vertigo lasting 20 minutes to 2 hours, accompanied by unilateral tinnitus, hearing loss, and a sensation of fullness in the left ear. Audiometry confirms low-frequency sensorineural hearing loss. MRI rules out retrocochlear pathology. She has failed conservative management with salt restriction and diuretics. What is the drug of choice for acute vertigo attacks in Meniere disease?