The comedian sparked uproar when she said former Obama adviser Valerie Jarrett, who is black, was the product of the Muslim Brotherhood and Planet Of The Apes.
Hours after US network ABC axed her show for her offensive tweet about former Obama adviser Valerie Jarrett, Barr was back on the social media platform.
She urged people not to defend her and said of her Jarrett tweet that she was “ambien tweeting” at 2am.
That led to the response on Twitter by the drug maker Sanofi.
Ashleigh Koss, a spokeswoman for Sanofi, which makes Ambien, said: “People of all races, religions and nationalities work at Sanofi every day to improve the lives of people around the world.
“While all pharmaceutical treatments have side effects, racism is not a known side effect of any Sanofi medication.”
Barr has said she had taken sleeping pills before comparing Ms Jarrett to an ape on Twitter. She said she was tired of being “attacked and belittled”.
In justifying her original tweet, Barr posted: “Guys I did something unforgiveable, so do not defend me.
“It was 2 in the morning and I was ambien tweeting. It was memorial day too. I went 2 far & do not want it defended. It was egregious Indefensible.
“I made a mistake I wish I hadn’t but...don’t defend it please.”
Barr later said: “”I think Joe Rogan is right about ambien. Not giving excuses for what I did(tweeted) but I’ve done weird stuff while on ambien-cracked eggs on the wall at 2am etc.”
The comedia served as a star and executive producer on the ABC show, which was a ratings phenomenon when it returned to US television earlier this year for a 10th series, after its original run came to an end in May 1997.
The 65-year-old actress and her co-star John Goodman reportedly earned about $250,000 (£190,000) per episode, according to Variety.
She earned about $21 million (£16 million) for acting, directing and producing the nine episodes of the new series, Slate reported.
The return was watched by an estimated 18.4 million viewers in the US and Donald Trump phoned Barr to congratulate her on the success.
Barr has apologised to her colleagues who lost their jobs after she sent the now-deleted tweet.
Responding to a fan on Twitter, she said she believed the show was axed because of a threatened boycott of the show’s advertisers.
Barr has previously apologised to Ms Jarrett, writing: “I want to apologize to you. I am very sorry to have hurt you. I hope you can accept this sincere apology!”
She also revealed she would be appearing on US comedian Joe Rogan’s podcast on Friday.
As well as the apology, Barr retweeted messages of support from fans who had backed the star using the hashtag #StandWithRoseanne.
One tweet juxtaposed Barr’s comparison of Ms Jarrett with an ape to other posts comparing images of Mr Trump to orangutans.
Following her original comments, Barr was widely condemned by celebrities including her own castmates.
Sara Gilbert, who played her on-screen daughter Darlene, wrote: “Roseanne’s recent comments about Valerie Jarrett, and so much more, are abhorrent and do not reflect the beliefs of our cast and crew or anyone associated with our show. I am disappointed in her actions to say the least.”
“This is incredibly sad and difficult for all of us, as we’ve created a show that we believe in, are proud of, and that audiences love- one that is separate and apart from the opinions and words of one cast member.”
Producer and comedian Wanda Sykes had already quit the show before it was revealed it had been cancelled and another of Barr’s co-stars, Emma Kenney, revealed she was ready to leave in protest at the comments.
Film director Ava DuVernay praised ABC entertainment boss Channing Dungey, tweeting: “For the record, this is Channing Dungey. Sitting on top of your world like a Queen in full judgement of your garbage and taking it out. #Roseanne.”
Shonda Rhimes, the creator of ABC shows Scandal and Grey’s Anatomy, tweeted: “Thank you, Channing. #justice.”
She added: “The terrible part is all of the talented innocent people who worked on that show now suffer because of this. #notjustice.
“But honestly she got what she deserved. As I tell my 4 year old, one makes a choice with one’s actions. Roseanne made a choice. A racist one. ABC made a choice. A human one.”
Ms Jarrett is yet to respond to Barr’s apology on Twitter, only tweeting a response to actress Julia Louis-Dreyfus, who had shared a selfie of the two of them.
Earlier, speaking on MSNBC, she said: “I’m fine. I’m worried about the people out there who don’t have a circle of friends and followers who come right to their defence.”