[48] However,

systematic research on the minimum or optimum dose of hypoxia for preacclimatization is still lacking. Preexisting pulmonary diseases[49] or Gefitinib migraine[24, 50] are associated with a predisposition for high-altitude disorders. Many travelers with other preexisting diseases (cardiovascular, neurological, hematological, musculoskeletal, etc.) or specific conditions (very young age, pregnancy, etc.) may plan to visit high altitudes. Advice and recommendations for them are far beyond the scope of this review, and the reader is referred to specific review articles and current international consensus guidelines.[35, 51, 52] Individual differences in responses to acute hypoxia can at least partly be tested by simple hypoxia challenge tests to identify AMS- and HAPE-susceptible individuals.[53, 54] Recently, in a large population of altitude visitors, it has been confirmed that chemosensitivity parameters

(high desaturation and low ventilatory response to hypoxia at exercise) are independent predictors for the development of severe high-altitude illness.[29] Unfortunately, the reliability and validity of using oxygen measurements to predict risk are far from perfect. Therefore, the experience from prior high-altitude exposures remains the best predictor of AMS susceptibility in future trips. Except for acetazolamide, the effectiveness of drugs used for the prevention of altitude illnesses Obeticholic Acid has been demonstrated in only a Clostridium perfringens alpha toxin limited number of trials. Drugs are recommended for those

with a history of AMS, a planned or forced rapid ascent (eg, Mount Kilimanjaro treks), or an expected rapid gain in sleeping elevation (>500 m) such as flying from Lima (sea level) to Cusco (about 3,400 m). Types of administration and doses are listed in Table 1. Pediatrics: 2.5 mg/kg every 12 hours Pediatrics: 2.5 mg/kg every 12 hours Pediatrics: should not be used for prophylaxis Both acetazolamide (125 mg a night) and temazepam (10 mg a night) can reduce sleep-disordered breathing at high altitude.[55-57] As the lowest dose of temazepam is recommended for use at high altitude, a 7.5 mg capsule could be used in countries where the 10 mg tablet is not available (eg, North America).[56] Nonsteroidal anti-inflammatory drugs or NSAIDs (eg, ibuprofen, naproxen, and aspirin) and acetaminophen can effectively prevent HAH, which is the key symptom of AMS.[58-60] Acetazolamide (Diamox, Cyanamid GmbH, Wolfratshausen, Germany) is the drug of choice for prevention of AMS, and is the only medication approved by the US Food and Drug Administration (FDA) for this purpose.[61] A dose of 125 mg taken twice daily, begun the day before ascent, is as effective as and has fewer side effects (see below) than 250 or 500 mg once a day.