The following agents may be used as prophylaxis In high attitude pulmonary edema -

nifedipine is used in the prophylaxis of HAPE Drugs are not as effective as descent from altitude and oxygen in the treatment of high-altitude pulmonary edema (HAPE). Nifedipine, by reducing pulmonary aerial pressure, may be effective in treating HAPE. These agents must be staed 24 hours before ascent and continued for 48-72 hours at altitude Ref Davidson 23rd edition pg 460