Adults with narcolepsy who have completed the TAK-994-1501 study will be able to take part in
this study.
The main aim of this study is to check if participants have side effects from TAK-994.
Participants will take one of 3 different TAK-994 dose for 8 weeks.
Then, half the participants will continue with their dose of TAK-994 and half will take a
placebo. In this study, a placebo will look like a TAK-994 tablet but will not have any
medicine in it. Participants will take TAK-994 or placebo for 4 weeks.
Participants will visit the clinic for a final check-up 2 weeks after their last dose of
TAK-994 or placebo.
The study doctors will check for side effects from TAK-994 and placebo throughout the study.
Participants will continue to record any narcolepsy symptoms as they did in Part B of the TAK
994-1501 study.