Limitless

Eddie Morra (Bradley Cooper), a struggling author suffering from writer's block, living in New York, is stressed by an approaching deadline. His girlfriend Lindy (Abbie Cornish), frustrated with his lack of progress and financial dependence, breaks up with him. Later, Eddie happens to run into Vernon (Johnny Whitworth), the estranged brother of Eddie's ex-wife, Melissa (Anna Friel). Vernon is involved with a shadowy, unidentified pharmaceutical company and gives Eddie a sample of a new "smart drug", NZT-48. Returning to his apartment, Eddie chooses to try out the drug and takes it seconds before being confronted by his landlord's wife due to his inability to pay the rent. As the drug begins to take effect, Eddie discovers he now has perfect recall and the ability to cross-correlate the most trivial and fleeting of past information and experiences into useful information, using it along with advanced powers of deduction to help her with a law school paper and seduce her. Entering his apartment, he feels immensely focused and begins to clean his apartment almost obsessively in a few hours. Struck with sudden inspiration, he begins writing a brand new book.
The next day, the effects having worn off, he brings the pages he wrote the night before to his publisher. Once he returns to his apartment, his publisher has left him several messages praising his writing. Eddie seeks out Vernon in an attempt to get more. But while Eddie is out running errands for him, Vernon is murdered. Eddie calls the police and then discovers Vernon's NZT-48 supply, as well as a ledger and a stash of money, just before they arrive. After giving a statement at the precinct, Eddie returns home and begins ingesting the drug daily. With the help of the drug's amazing effects, Eddie spends a few weeks cleaning up his lifeâfinishing his book, getting fit, dressing better and making friends with a group of young jet-setters. They take him on vacation to Europe where Eddie experiments further with his new-found abilities, being able to instantaneously learn and analyze new information such as being fluent in new languages after only hearing a few words, doing advanced mathematics in order to gamble, and having increased hand-eye coordination. The only apparent side effects are a peculiar bluish-green hue in his irises and a constant need to keep moving forward, as well as increased confidence and ambition.
Testing his analytical skills on the stock market with Vernon's stash of money, Eddie quickly makes large returns on small investments. Realizing he requires more capital, he borrows 100K from a Russian loan shark, Gennady (Andrew Howard), and is hired at a brokerage firm thanks to one of his new acquaintances, where he quickly parlays this capital into two million dollars plus. He further increases his NZT-48 dosage and begins to rekindle his relationship with Lindy.
Eddie's prodigious success leads to a meeting with a finance tycoon, Carl Van Loon (Robert De Niro). He tests Eddie by seeking advice on a merger with Hank Atwood's (Richard Bekins) company. Walking through Manhattan after the meeting, Eddie starts experiencing hallucinations and the sense of time skipping forward, noticing that several hours have suddenly passed of which he has no memory. As this effect recurs over the course of the day and night he finds himself at a nightclub, a hotel party, in a hotel room with a blonde woman (Caroline Winberg), and in a subway station where he easily subdues several muggers who attack him (thanks to the effects of NZT-48). When this series of blackouts finally ends, he finds himself standing on the Brooklyn Bridge at dawn, 18 hours having passed for which he cannot account. He slowly limps home. During another meeting with Van Loon, Eddie sees a news report detailing the murder of the blonde woman whom he had presumably slept with, but he is unable to remember whether or not he was the killer. Running out of the meeting, he vomits and becomes severely ill.
Eddie goes through Vernon's ledger and discovers that everyone taking NZT-48 is either in the hospital or dead. When he calls another number, a man in a tan trench coat (Tomas Arana) is revealed to have been to be following him when he answers the phone from behind Eddie, and gives chase before Eddie loses him. Eddie meets with Melissa and discovers that she too had been on NZT-48. She informs him that when she attempted to stop taking it, she had experienced a severe mental rebound effect, as well as a limp like Eddie, and that there are several people who have died after abruptly quitting. On his way home, Eddie is accosted by Gennady, who takes Eddie's last NZT-48 pill. Eddie visits Lindy and asks her to retrieve his backup stash, which he had hidden in her apartment. On her way back, she is followed by the man in the trench coat. He corners Lindy in a park and kills two unfortunate men who try to protect her. Eddie tells her to take one of the pills. This enables her to escape, and she returns the stash to Eddie.
Eddie experiments with the drug and learns to control his dosage, sleep schedule, and food intake to prevent side effects. He continues to earn money on the stock exchange and hires bodyguards to protect him from Gennady, who threatens him in an attempt to obtain more NZT-48. He buys an armored penthouse and hires a laboratory in an attempt to reverse engineer the mysterious drug. For his part in Carl Van Loon's merger, Eddie is promised forty million dollars, and he hires an attorney (Ned Eisenberg) to help keep the police from investigating the deaths of both Vernon and the woman.
On the day of the merger, Atwood's wife informs Van Loon that he has fallen into a coma. Eddie recognizes Atwood's driver as the man in the trench coat and realizes Atwood is on NZT-48. While Eddie participates in a lineup, his attorney steals Eddie's whole supply of NZT-48 from his jacket. Soon afterward, Eddie discovers that his pills are gone and begins to enter withdrawal. He also learns that his bodyguards have been killed. But the severe effects of withdrawal cause him to hurry home when Van Loon questions him about his knowledge relating to Atwood's coma. Gennady breaks into his apartment, demanding more NZT-48. He reveals that to increase the effect's potency and duration he has been dissolving it in water and injecting it intravenously. Eddie stabs Gennady and licks up some of his pooling blood for the NZT-48 it now contains. His increased mental acuity restored, Eddie kills Gennady's henchmen and escapes. He meets with the man in the trench coat, surmising that Atwood employed the man to locate more NZT-48. The two join forces and recover Eddie's stash from his attorney.
A year later, Eddie has retained his wealth, published a book (entitled "Illuminating the Dark Fields," a play on the name of the book, The Dark Fields, which the movie is based on), and is running for the United States Senate. Van Loon visits him and reveals that he has absorbed the company that produced NZT-48 and shut down Eddie's laboratory. He offers a steady supply of the drug in return for power when Eddie eventually and inevitably becomes President of the United States. Eddie implies that he has had multiple laboratories working on the drug for the purposes of reverse engineering it, as well as being able to eliminate all of the negative side-effects. He states that he has found a way to wean himself completely off of the drug without losing any of his enhanced abilities. He turns down Van Loon and sends him on his way. He meets Lindy at a Chinese restaurant for lunch, where his Chinese language skills with the waiter indicate that, whether he still relies on the drug or not, his enhanced abilities are still completely intact.[citation needed]

Question: What chemical causes everyone who takes it to be sick or dead?
Answer: NZT-48