[Problem of orthostatic intolerance in astronauts and perspectives for its pharmacological prevention].

Double-blind placebo-controlled method was applied to study venoconstrictor agent Dihydroergotamine effects on orthostatic tolerance in 8 healthy male-volunteers after 6-hour exposure to antiorthostatic stress (-6 degrees). The drug was able to induce blood centralization and diuresis additional to those caused by the simulated microgravity per se and failed to prevent the orthostatic intolerance. In 6 subjects the studies were repeated with the occlusive cuffs used in order to prevent venous blood return from the vascular bed of the lower limbs during 0-gravity simulation. The occlusive cuffs were shown to eliminate the additional drug-induced blood centralization and diuresis. Orthostatic tolerance in this case occurred to be less affected than in the case of no countermeasure used or in the case when dihydroergotamine was used alone. Thus, it was shown that mechanical prevention of the drug-induced blood centralization from being realized in 0-gravity simulation must be considered as the requirement necessary to permit the drug to perform its beneficial effect on the orthostatic tolerance after the real or simulated weightlessness.