Drug Use at High Terrestrial Altitudes and in Cold Climates: A Brief Review

Acetazolamide, methazolamide, and spironolactone taken prophylactically generally produce a reduction in the occurrence of symptoms of Acute Mountain Sickness (AMS), but are not a panacea. Such prophylactic use may indirectly improve exercise performance due to the alleviation of AMS symptoms. Dexamethasone, phenytoin, and furosemide effectiveness remains uncertain, and more controlled studies are indicated. Antacids apparently provide no relief from AMS. Valium is contraindicated at altitude because it produces mind altering effects at a time when preservation of mental competence is critical. A report claiming the usefulness of nifedipine in treating High Altitude Pulmonary Edema (HAPE) during a mountain climb warrants further investigation. Partial alleviation of the presumably synergestic cold-air and exerciseinduced asthma can be achieved in many so afflicted by premedication with cromolyn sodium or its combination with terbutaline sulphate. Attempts to use thyroid hormone or triiodothyronine for the stimulation of heat production and peripheral vasodilators for increasing skin and other peripheral temperatures in order to prevent cold injury to tissue have thus far yielded inconclusive results. The focus of this review is on some drugs that have been used at high terrestrial altitudes or in cold climates in the prevention or treatment of environmentally produced adverse reactions and disabling conditions. Minor mention is made of some drugs used to treat medical problems that occur in such environments. Human ventures into extreme environments have led to a variety of adverse reactions to these environments. Many of the problems that arise can be minimized with proper planning that involves selection and use of appropriate clothing, nutrition, and pharmaceuticals. Knowledge of warning signs can be gained through pre-exposure education. Nevertheless, many go unprepared and suffer the consequences. Certain medications have proven effective in many cases to prevent or alleviate symptoms and to treat further complications. Considerable research has been done in some areas, but not in others, which limits a discussion of drug usefulness with respect to the consequences of exposure to hypoxia and/or cold. A brief summary of the drugs discussed and their actions is presented in Table 1. laboratory for Human Performance Research, The Pennsylvania State University, University Park, PA 16802 Human Biology, October 1988, Vol. 60, No. 5, pp. 663-677 © Wayne State University Press, 1988 This content downloaded from 157.55.39.210 on Sun, 31 Jul 2016 05:10:43 UTC All use subject to http://about.jstor.org/terms 664 / D. BEECKMAN AND E. R. BUSKIRK Drug Use at High Terrestrial Altitudes. Ascending to high terrestrial altitudes may place considerable stress on the body because of the necessity to exercise when hypoxic during exposure to arid, windy, cold and frequently stormy conditions. Solar radiation may also be high. This combination of stresses over the short term evokes a variety of physiological strains associated with hypoxia: body cooling and water loss. Exposure to hypoxia over time improves a person's tolerance to the availability of fewer oxygen molecules, a process known as acclimation (chamber exposure) or acclimatization (natural exposure). Certain conditions such as Acute Mountain Sickness (AMS) or High Altitude Pulmonary Edema (HAPE) arise when one ascends a mountain too fast or is poorly acclimatized (Hackett and Rennie 1976; Houston 1983). Various drugs have been investigated for their effectiveness in reducing AMS symptomatology and/or the occurrence of such symptoms using both simulated altitudes in hypobaric chambers and the natural conditions experienced on the mountains of the world. Common ailments such as some microbial infections, gastrointestinal disorders and superficial injury can be treated with available medications (Huber 1986; Mountaineers 1985), but in most instances such medications should be dispensed by qualified medical professionals following a thorough evaluation of the patient. Carbonic Anhydrase Inhibitors. A syndrome that frequently occurs upon ascending to higher altitudes is AMS. The most frequent symptoms reported are headache, weakness, nausea, dyspnea and disturbed sleep (Hackett and Rennie 1976; Houston 1983). The most common and widely studied carbonic anhydrase (CA) inhibitor used in the management of AMS is acetazolamide which acts both on CAI and CAII the former in red blood cells and the latter in muscle and other tissue, particularly the kidney. Carbonic Acid Buffering System.