URINARY-EXCRETION OF MEPERIDINE AND NORMEPERIDINE IN MAN UPON ACUTE AND CHRONIC EXPOSURE TO HIGH-ALTITUDE

The urinary excretion of unchanged meperidine (M) varies with change o f pH and metabolism. Since exposure of man to high altitude (H) may ca use significant physiologic changes, we investigated its effects on th e urinary excretion of M. The study was carried out in 3 groups of hea lthy, male volunteers (ages 18-20 years): at sea level (L), at 4360 m the day after arrival at H(HA), and at 4360 m bt subjects residing for >10 months at H(HC). Urine was collected for the periods of 0-4, 4-8, 8-12 and 12-24 h. Urinary pH was measured and the concentrations of M and normeperidine (N) were determined. The 24 h excretion of M and N was significantly decreased fort vs. HA and L vs. HC. Significance was also seen for the periods 0-4, 4-8 and 8-12 h. The ratio of amount ex creted M/N for the 24 h period was highly significant for L vs. HA and L vs. HC. The urinary pH ranged from 5.3-5.9 for L, 5.9-7.0 for HA, a nd 5.1-5.7 for HC. The F-el (fraction of M eliminated in the unchanged form ill urine) significantly decreased fron L to HA and HC.