This movie is not totally about drugs. The drugs help one travel to different times throughout your life, but Fred can do this without the drugs which is why he's able to travel 13 years later.
Fred thought he was looking for Cindy for most of the movie and finally finds her where they are living as bums and able to travel to different realities. When he visits his mom, she licks her lips and the flashes of mouths that he's been seeing throughout the movie are his mom's that he thought were Cindy's, the person he's been searching for. After realizing this, he tells Cindy he can't stay with her because it wasn't her he was looking for.
Fred decides to make other decisions in the past and present (taking his final and letting Cindy walk away in the past, and doing his work presentation successfully in the future).
In the end is actually the beginning of the movie in the past. Fred's mom tells baby Fred not to crawl to the door and to remember what happened last time. Last time was an alternate choice he made but has not happened in the current reality they are in. Baby Fred remembers and decides to go to his mom instead of almost falling down the stairs, showing the mom knows about time not being linear.
All along it was his mom introducing him to nonlinear time, not Cindy and the drugs; the drugs just enhanced the effects.
I hope this explanation was clearer than the movie for those that didn't understand.
Fred thought he was looking for Cindy for most of the movie and finally finds her where they are living as bums and able to travel to different realities. When he visits his mom, she licks her lips and the flashes of mouths that he's been seeing throughout the movie are his mom's that he thought were Cindy's, the person he's been searching for. After realizing this, he tells Cindy he can't stay with her because it wasn't her he was looking for.
Fred decides to make other decisions in the past and present (taking his final and letting Cindy walk away in the past, and doing his work presentation successfully in the future).
In the end is actually the beginning of the movie in the past. Fred's mom tells baby Fred not to crawl to the door and to remember what happened last time. Last time was an alternate choice he made but has not happened in the current reality they are in. Baby Fred remembers and decides to go to his mom instead of almost falling down the stairs, showing the mom knows about time not being linear.
All along it was his mom introducing him to nonlinear time, not Cindy and the drugs; the drugs just enhanced the effects.
I hope this explanation was clearer than the movie for those that didn't understand.