Diazepam and meclizine have been shown to be effective as anti-motion sickness drugs. Quantitative studies of the most easily measured feature of the balance system, the vestibuloocular reflex (VOR), have shown these drugs decrease both its gain and time constant. Since motion sickness does not occur in patients who have lost their VOR, many investigators believe that decreasing the VOR should lessen the severity of, or susceptibility to, motion sickness. The specific aim of the proposed study is to investigate if a drug's motion sickness efficacy correlates with its ability to change the VOR. Using two different classes of medications will help determine if a change in the VOR is responsible for the anti-motion sickness susceptibility.
A minor aim is to use well-established and accepted linear control system models of the VOR to simulate the observed changes in the VOR after medication. This may help to localize the portion of VOR function that is most affected by the drugs. Often functional localization suggests anatomical localization.
Motion sickness and vestibular dizziness (vertigo) are not identical, but they share many physiological components. Almost all drugs that are used in treating motion sickness are used in treating vertigo. Thus motion sickness therapy has direct clinical significance for the treatment of dizzy patients. There are several advantages to understanding the mechanism of action of drugs used in motion sickness such as diazepam and meclizine: health care providers could tailor specific medications to specific problems; if a patient is not responding to a drug, their VOR can be tested to determine if the medication is inducing the desired physiological response; pharmaceutical companies can design better medications; and correlating anti-motion sickness protection with easily obtained physiologic responses could result in a more rapid and less expensive initial screening method of drug effectiveness.
This study is intended as a pilot study for an R01 that
will investigate other drugs and consider the linear VOR.