[The pharmacodynamics and pharmacokinetics of furosemide during ordinary life activities and during head-down tilt hypokinesia in a healthy subject].

The object of the work was comparative study of the characteristics of pharmacodynamics and pharmacokinetics of the diuretic furosemide during ordinary vital activity of man and under conditions of antiorthostatic hypokinesia. Six practically healthy males were examined. They took part successively in two experimental series: series 1--during an ordinary motor regimen under ambulatory conditions; series 2--under conditions of antiorthostatic hypotension (ANOH, 12 degrees). In both series with absolute correspondence of the procedures and order of manipulations the subjects were given 40 mg furosemide per os, venous blood and urine were repeatedly tested, and the physiological data were recorded. In combined action of an antiorthostatic position of the body and the diuretic an additive effect was encountered, i.e., increased therapeutic effect of, furosemide. The blood serum electrolyte composition practically did not change in this case. After oral administration of 40 mg furosemide maximal concentration of the drug in the blood (977 +/- 151 ng/ml) was found on the average in a group in 1.3 +/- 0.2 h. The drug half-life period in this case was 1.1 +/- 0.4 h; total clearance was 24.7 +/- 2.8 liter/h, and the distribution volume was 33.7 +/- 12.7 liters. In maintenance of antiorthostasis furosemide pharmacodynamics and pharmacokinetics changed but the individual character of the dynamics of drug concentration in the blood persisted. No statistically significant differences in the mean group pharmacokinetic parameters of the drug during an ordinary motor regimen and in antiorthostatic hypokinesia were encountered. Furosemide given in antiorthostatic hypokinesia led to diminished filling of the upper and middle parts of the lungs with blood despite the attendant decrease in the tonus of the resistant vessels.