Carbonic anhydrase inhibitors for prevention of space motion sickness: an avenue of investigation.

Space motion sickness (SMS) is an important medical problem facing NASA's space shuttle program. Two theories that have been advanced to explain SMS are the "fluid shift theory" and the "vestibulo-ocular sensory conflict theory". The "fluid shift theory" pre-supposes an active or passive shift of body fluid to the central nervous system (CNS) and vestibulo-auditory mechanisms. In contrast, the "sensory conflict theory" hypothesizes that unfamiliar accelerational and gravitational inputs from the middle ear conflict with visual inputs and lead to SMS. Carbonic anhydrase inhibitors (CAHI) are known to suppress active production of CSF and may be able to inhibit production of perilymph in the semi-circular canals. Therefore, CAHI may be able to diminish the hypothesized fluid shift to the CNS and inner ear under the fluid shift theory. It is suggested that carbonic anhydrase inhibitors merit clinical investigation to test their usefulness for prophylaxis of space motion sickness and to test the veracity of the fluid shift theory.