WMG: Limitless

Eddie was still on NZT-48 at the end of the movie.
The whole being off of NZT-48 but still keeping most of the brain processing power with it thing, was Eddie lying to Carl to avoid his threats. After all, NZT-48 does make you feel "invincible", and it is not approved and illegal. He would also probably be lying to Lindy as well.
  • This is supported by the fact the he offhandedly states that he has more than one lab. Why bother bringing that up, if he was off the stuff anyway?
  • He also says that he "tweaked" it. He's not on NZT, he's on something similar that the labs managed to cook up for him that isn't quite as dangerous. (And NZT was never actually illegal, it just doesn't exist as far as any regulatory agency is concerned - you can't get a prescription for it, but the DEA isn't going to come busting down your door if you have a supply. In the real world, there are lots of rejected or experimental drugs that you can buy from chemical supply companies as "research chemicals" without attracting too much attention.)
  • According to the sequel series, he's still on NZT but is taking regular injections of some kind that keep the adverse effects at bay.

NZT was actually just a really small amount of meth, modified to be ingested orally.
Pretty self-explanatory. Eddie was addicted to meth and only felt "limitless" when on it. He already had the ability to become an investment genius etc. It just made him extremely focused and organized. This also fits with the fact that the 90% of Your Brain theory is just a myth.
  • Doesn't explain his expertise on law based on glimpses of a law textbook in his college days or speaking Russian by hearing the Russian thugs.
  • Non-fantastic aspects of NZT resemble Cocaine, MDMA, and also amphetamines. Amphetamine has been used in armies and airforces to heighten awareness of soldiers and pilots.

NZT is used by the Assassins of Assassin's Creed.
The real life Assassins used Hashish (aka cannabis) so they already have a taste for mind-altering drugs. Add the fact that NZT makes you like jumping off high places and better at fighting multiple enemies, and it seems obvious that NZT would their drug of choice. It also meshes well with the Assassin's philosophy: that people are free to risk their own mistakes in an attempt to become better people.
  • Eagle Sense also seems to be a way of representing NZT's heightened insight.

NZT has side effects not specifically explained in the film.
In addition to the side effects portrayed in the film, NZT also messes with your impulse control and ability to see long-term consequences for your actions. This explains Eddie's unwillingness to just wait a couple days to get his $100,000, and later unwillingness to wait a couple more to get his $40,000,000. This also accounts for his failure to pay back the loan shark. His entire life begins to revolve around getting more money and more importance, the two things he felt he lacked in the beginning of the film. Hence he gains money and runs for senate, but doesn't seem to have any sort of endgame in mind.
  • It turns out that when the really nasty side effects start, it kills within a couple of days unless the user stops taking NZT right away. It's essentially what happened to Eddie when he overdosed on NZT but Up to Eleven. You suffer blackouts, horrifying hallucinations and you brain starts frying. However, the effects of the sudden withdrawal can be just as debilitating and also end in madness and/or death.
    • To see the details of the side effects are actually quite horrifying. But the worst part is that the Side Effect Neutralizer that Eddie has concocted ALSO has side-effects. See normally the only way to deal with NZT Withdrawal is either to take that shot, or to keep taking NZT like clockwork. For the most part it works as we see multiple people who have to take NZT basically daily without the shot still function fine as long as they keep taking it. However with the side effect shot while you may be immune to the withdrawal symptoms for the few months it's active, the second it starts wearing off you get the immediate feedback to all the withdrawal systems even WHILE ON NZT. Even taking NZT doesn't save you. It's why you see Brian barely function even while on the pill during the time the shot was wearing off and was basically about to die if Eddie didn't intervene. So with the shot, while you may no longer be reliant or dependent on daily NZT usage to live, you become reliant on the shot itself. It's possible that if you wean yourself off of NZT in the timeframe of the shot you might avoid the blowback but if NZT is hard enough to drop when the nasty side effects hit you almost immediately, imagine trying to justify doing it when you only have to worry about them every few months.

Mike and Ike's names are actually Mike and Ike
Brian was trolling the audience when he said that he forgot them. He did it for the lulz!
  • Ike is actually named Jason.

The show will eventually cross over with Elementary
Both are CBS shows set in New York that feature cloudcuckoolander leads who are exceptionally good at observation and deduction and have a female colleague keeping them grounded. It could lead to interesting debates between Sherlock and Brian. Limitless airs the day before Elementary, which means a plot starting in the former can easily end in the latter without much fuss.