Pharmacodynamic aspects of spaceflight.

Little is known at present about the effects of human exposure to microgravity on the pharmacodynamics of medicinal agents. Considering the known physiologic perturbations associated with spaceflight and the effects of some of these perturbations on the pharmacodynamics of certain medicinals that act on the central nervous system, it is likely that the pharmacodynamics of at least some of these agents will be altered in individuals who are subjected to microgravity and other conditions of spaceflight. It is timely to initiate formal studies, initially in ground-based animal models and human volunteers during prolonged, head-down bed rest and eventually in animals and human volunteers exposed to microgravity, of pharmacodynamics and pharmacokinetics during spaceflight.