***TASK*** the task is to summarize an input biomedical literature in six sentences 
    ***INPUT*** the input is a biomedical literature 
    ***OUTPUT*** the output is the summary of an input biomedical literature in six sentences 
    ***DOCUMENTATION*** 
    ***EXAMPLES*** 
    Input: As part of a double-blind trial slow-release acetazolamide ( 500 mg daily ) or placebo was given to 20 men ascending to 5000 m. In the 18 who attained this altitude , those on acetazolamide had fewer symptoms of acute mountain sickness ( AMS ) than those on placebo ( p < 0.02 ) . 10 of the men had been to 5400 m on a previous expedition . 5 of these men took acetazolamide and 5 took placebo . Those on the drug performed better than those on placebo ( p < 0.005 ) . Furthermore , the performance of the 5 men on acetazolamide during the second expedition had improved more than that of the men on placebo ( p < 0.01 ) . In the group as a whole the symptoms of AMS were negatively correlated with arterial oxygen tensions ( p < 0.001 ) which were higher in the drug group ( p < 0.001 ) . Acetazolamide probably had its effect by causing a metabolic acidosis with a result ant increase in respiratory drive and arterial oxygen tension In this r and omized , double-blind placebo controlled trial our objectives were to determine if acetazolamide is capable of preventing high altitude pulmonary edema ( HAPE ) in trekkers traveling between 4250 m (Pheriche)\4350 m ( Dingboche ) and 5000 m ( Lobuje ) in Nepal ; to determine if acetazolamide decreases pulmonary artery systolic pressures ( PASP ) at high altitude ; and to determine if there is an association with PASP and signs and symptoms of HAPE . Participants received either acetazolamide 250 mg PO BID or placebo at Pheriche\Dingboche and were reassessed in Lobuje . The Lake Louise Consensus Criteria were used for the diagnosis of HAPE , and cardiac ultrasonography was used to measure the velocity of tricuspid regurgitation and estimate PASP . Complete measurements were performed on 339 of the 364 subjects ( 164 in the placebo group , 175 in the acetazolamide group ) . No cases of HAPE were observed in either study group nor were differences in the signs and symptoms of HAPE found between the two groups . Mean PASP values did not differ significantly between the acetazolamide and placebo groups ( 31.3 and 32.6 mmHg , respectively ) . An increasing number of signs and symptoms of HAPE was associated with elevated PASP ( p < 0.01 ) . The efficacy of acetazolamide against acute mountain sickness , however , was significant with a 21.9 % incidence in the placebo group compared to 10.2 % in the acetazolamide group ( p < 0.01 ) . Given the lack of cases of HAPE in either group , we can draw no conclusions about the efficacy of acetazolamide in preventing HAPE , but the absence of effect on PASP suggests that any effect may be minor possibly owing to partial acclimatization during the trek up to 4200 Self-rated moods were determined twice daily with the Clyde Mood Scale on 35 human subjects at 200 m ( baseline ) during a study concerned with evaluating the efficacy of staging plus acetazolamide ( treatment ) for the prevention of acute mountain sickness ( AMS ) . Mood states also were determined on all subjects at 4300 m ( Pikes Peak , Co ) and on 18 of these subjects at 1600 m ( staging site ) . Mood state changes were not observed at 1600 m , but four of the six mood factors were sensitive to the 4300 m altitude . At 4300 m , all subjects , treatment and control , rated themselves as less friendly and clear thinking and more sleepy and dizzy . At 4300 m , the treatment strategy result ed in an improved mood on the friendly , sleepy , and dizzy factors . Altitude-induced changes in clear thinking were not altered by the treatment strategy Acetazolamide treatment ameliorates the symptoms of AMS ; however , the mechanism by which this occurs is unclear . To examine the effects of acetazolamide on oxygenation , CO2 responsiveness and ventilatory pattern during acute exposure to HA , we studied two groups of subjects at SL and following rapid ( less than 8 h ) transport to HA .  Acetazolamide or placebo tablets were given to groups 1 and 2 , respectively , in a double-blind manner after baseline SL measurements ; treatment was continued during HA exposure . There was no difference in the ventilatory pattern at HA , between the two groups . While the Ve achieved in response to CO2 at HA vs SL was much greater in each group the percent change from baseline at HA versus that at SL was not significantly different . The beneficial effects of acetazolamide in AMS are associated with a higher level of ventilation at HA and better oxygenation : CO2 chemosensitivity is not affected by acetazolamide at HA Acute mountain sickness ( A.M.S. ) and its severe complications , high-altitude pulmonary oedema ( H.A.P.O. ) and cerebral oedema ( C.O. ) , were studied in 278 unacclimatised hikers at 4243 m altitude at Pheriche in the Himalayas of Nepal . The overall incidence of A.M.S. was 53 % , the incidence being increased in the young and in those who flew to 2800 m , climbed fast , and spent fewer nights acclimatising en route . It was unrelated to sex , to previous altitude experience , to the load carried , and to recent respiratory infections . The severity of A.M.S. was inversely related to age ( independent of rate of ascent ) and the highest altitude attained , and was highly ocrrelated with speed of ascent . There were 7 cases of H.A.P.O. and 5 with the more intractable C.O. and , of these 12 , 11 had flown in , 9 had spent only one night at Pheriche , and none were on acetazolamide . 11 required evacuation .  Acetazolamide , compared in a double-blind study with a placebo and also compared with no tablets at all , reduced both the incidence and the severity of A.M.S. in those who flew to 2800 m but not in those who hiked up to that altitude . Prevention consists in slow ascent , rapid recognition of warning signs , and prompt descent to avoid progression Abstract Objective To evaluate the efficacy of ginkgo biloba , acetazolamide , and their combination as prophylaxis against  acute mountain sickness . Design Prospect i ve , double blind , r and omised , placebo controlled trial . Setting Approach to Mount Everest base camp in the Nepal Himalayas at 4280 m or 4358 m and study end point at 4928 m during October and November 2002 . Participants 614 healthy western trekkers ( 487 completed the trial ) assigned to receive ginkgo , acetazolamide , combined acetazolamide and ginkgo , or placebo , initially taking at least three or four doses before continued ascent . Main outcome measures Incidence measured by Lake Louise acute mountain sickness score ≥ 3 with headache and one other symptom . Secondary outcome measures included blood oxygen content , severity of syndrome ( Lake Louise scores ≥ 5 ) , incidence of headache , and severity of headache . Results Ginkgo was not significantly different from placebo for any outcome ; however participants in the acetazolamide group showed significant levels of protection . The incidence of acute mountain sickness was 34 % for placebo , 12 % for acetazolamide ( odds ratio 3.76 , 95 % confidence interval 1.91 to 7.39 , number needed to treat 4 ) , 35 % for ginkgo ( 0.95 , 0.56 to 1.62 ) , and 14 % for combined ginkgo and acetazolamide ( 3.04 , 1.62 to 5.69 ) . The proportion of patients with increased severity of acute mountain sickness was 18 % for placebo , 3 % for acetazoalmide ( 6.46 , 2.15 to 19.40 , number needed to treat 7 ) , 18 % for ginkgo ( 1 , 0.52 to 1.90 ) , and 7 % for combined ginkgo and acetazolamide ( 2.95 , 1.30 to 6.70 ) . Conclusions When compared with placebo , ginkgo is not effective at preventing acute mountain sickness . Acetazolamide 250 mg twice daily afforded robust protection against symptoms of acute mountain sickness The study objective was to determine whether acetazolamide is effective in prophylaxis of acute mountain sickness ( AMS ) at moderate altitude in ambulatory travelers not undergoing vigorous exercise . Volunteers vacationing in La Paz , Bolivia ( 3630 m ) , immediately after arrival from sea level were studied . The design was a double-blind , r and omized trial of two doses of acetazolamide ( 125 mg twice daily , 250 mg twice daily ) versus placebo twice daily over a 24-h period . The main outcome measure was AMS score and score trend , using the Lake Louise consensus question naire . Nine of 32 subjects ( 28 % ) had symptom scoring diagnostic of AMS at 0 h. At 0 and 24 h ( respectively ) , the mean Lake Louise scores were 1.73 and 1.09 for the 11 subjects receiving placebo , 1.45 and 1.36 for the 11 subjects receiving the 125-mg dose , and 2.7 and 0.6 for the 11 subjects receiving the 250-mg dose . The absolute change in these mean scores was not significant for placebo ( p = 0.21 ) or the 125-mg dose ( p = 0.88 ) , but was significant for the 250-mg dose ( p = 0.008 ) . A comparison of a difference in decline in average AMS score over time showed a statistically significant decline for the 250-mg dosing group versus placebo ( p = 0.002 ) . The 250-mg dose of acetazolamide twice daily ( but not 125 mg twice daily ) was effective in inducing a significant decline in AMS symptoms over the 24-h period after arrival to 3630 m. These results suggest that the dosing of acetazolamide for AMS prevention in nonmountaineering tourists at altitudes below 3700 m should not be lowered below 250 mg twice daily Previous studies have shown low-dose acetazolamide to be effective in preventing AMS in persons already at high altitude and then moving higher , a relatively low risk situation . We wished to evaluate prophylactic administration of low-dose acetazolamide for reducing the incidence and severity of AMS in a high-risk setting : rapid ascent from 1600 to 4300 m. We performed a double-blind , r and omized , placebo-controlled study with human subjects ( n=44 ) exposed to 4300 m for 24 h. Subjects were treated for 3 days prior to ascent to 4300 m and during day 1 at altitude with placebo ( n=22 ) or acetazolamide 250 mg/day ( 125 mg bid , n=22 ) . AMS diagnosis required both an AMS-C score from the Environmental Symptom Question naire-III > or=0.7 and a Lake Louise Symptom ( LLS ) question naire score > or=3 plus headache .  Acetazolamide reduced the incidence of AMS compared to placebo-treated subjects ( 14 % vs. 45 % , respectively , p=0.02 ) , and the number needed to treat was 3 . The AMS-C and LLS scores were lower in acetazolamide-treated subjects , indicating less severe AMS . Low-dose acetazolamide administered prior to ascent and on day 1 at 4300 m effectively reduced the incidence and severity of AMS in a high-risk setting Abstract Objective .—This study aim ed to determine the efficacy , tolerability , and practicality of acetazolamide for the prevention of acute mountain sickness ( AMS ) in Nepali trekking porters early in the trekking season . Methods .—This study was a r and omized , double-blind controlled trial with 400 male Nepali porters in the Mount Everest region of Nepal , trekking from Namche Bazaar ( 3440 m ) to Lobuche ( 4930 m ) , the study endpoint . Participants were r and omized to receive 250 mg acetazolamide daily or placebo , and AMS symptom scores ( Lake Louise ) were compared in highl and ers vs lowl and ers . Results .—Only 109 ( 27.2 % ) of the 400 porters completed the trial ( 28 highl and ers , 81 lowl and ers ) . The rest either dropped out ( 275/400 porters , 68.8 % ) or were excluded ( 16/400 porters , 4 % ) . Acute mountain sickness occurred in 13 ( 11.9 % ) of 109 porters ; all were lowl and ers ; 7 were taking acetazolamide , 6 taking placebo .  Birthplace , acclimatization in the week before the trial , ascent rate , and rest days were the most important variables affecting the incidence of AMS . No highl and ers , but 13 (  
    Output:
    
Acetazolamide in doses of 250 mg , 500 mg , and 750 mg daily are all more effective than placebo for preventing acute mountain sickness .
Acetazolamide 250 mg daily is the lowest effective dose to prevent acute mountain sickness for which evidence is available