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There is evidence that phenytoin is effective in preventing
motion sickness according to five original research articles.
One research article involved seven participants who were
given phenytoin and underwent simulated motion. Phenytoin
was found to be four times as effective as any other single
agent in increasing tolerance to motion stress.
Another study involved 15 seamen and/or divers who participated
in both small-boat trials lasting one hour and operational
sea travel lasting two to four days. The participants were
given phenytoin in loading doses in the 24 hours before the
trials and then maintained at anticonvulsant levels or a placebo.
In both the small-boat trials and the sea-travel phase, the
participants showed a significant reduction in nausea levels
with the phenytoin as compared with the placebo.
Further, in a study of nine participants who underwent a
series of exposures to rotational movement, including sea
travel, phenytoin was found to effectively reduced motion
sickness.
Another study focused on the effects of phenytoin on cognition
and performance. Participants were given phenytoin to anticonvulsant
levels or placebo. At regular doses, phenytoin did not cause
a decrease in functional abilities, however in higher doses
participants reported side effects such as lightheadedness.
A final study with 35 participants compared placebo with
the use of a single dose of phenytoin taken four hours before
participants were spun round inside a rotating drum. Significant
differences between the effectiveness of phenytoin and placebo
were not found, however there were significant behavioral
responses, such as vomiting and requests to stop the study
early, which may have influenced the results.
Most of the studies used the approach of rapidly loading
subjects up to anticonvulsant levels of phenytoin in the preceding
24 hours, which is not practical for clinical use. Further,
the studies do not represent a widespread sample, as they
were all small and included only healthy adult males.
Although it appears that short-term use of phenytoin for
motion sickness would not produce serious problems, further
research is required. Further, phenytoin is known to interact
with some commonly used medications, which should be taken
into account if it is to be prescribed for preventing motion
sickness.
Medical
Journal Australia June 2, 2003;178(11):575-6
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