Final answer:
The treatment of choice for preventing acute mountain sickness is Acetazolamide, a carbonic anhydrase inhibitor that facilitates acclimatization at high altitudes. Dexamethasone can be used for severe cases but is not the primary preventative medication.
Step-by-step explanation:
The treatment of choice in preventing acute mountain sickness (AMS) is Acetazolamide. This medication is a carbonic anhydrase inhibitor, which helps to mitigate symptoms of AMS by increasing urinary bicarbonate excretion, thereby creating a metabolic acidosis and facilitating acclimatization as one ascends to higher altitudes. When used prophylactically, it helps in reducing the incidence and severity of AMS.
Dexamethasone is another medication that is sometimes used for the prevention and treatment of severe AMS and high-altitude cerebral edema. However, it is not considered the first choice for preventing AMS. Ginkgo biloba and Nifedipine may also have roles in the prevention or treatment of certain high-altitude illnesses but are not the primary drugs of choice for preventing AMS.