After Roseanne Barr tweeted racist comments about former Obama staffer Valerie Jarrett, ABC cancelled her show , and her agent dropped her. Although she’s since deleted the tweet, the mistake cost her and countless others their livelihoods. Barr then tweeted an apology , and even said she’d be leaving Twitter . So far, she hasn’t. In fact, she’s been especially active on the site, issuing another statement at 11pm US Pacific time—local time for Barr—yesterday (May 29) blaming the sleep aid Ambien for her behavior. This tweet, too, was deleted, around 3:20am Pacific, Gizmodo reports . Ambien, manufactured by Paris-based Sanofi-Aventis, has been putting people to sleep for some 25 years, since it first received approval from the US Food and Drug Administration in 1992. The drug, known generically as zolpidem, works by increasing the effectiveness (paywall) of a neurotransmitter called gamma-aminobutyric acid, or GABA, which inhibits overactive cells. This works partially to quiet th...