“It was 2 in the morning and I was ambien tweeting”

That’s how Roseanne Barr explained her now-infamous slur about Valerie Jarrett, a former senior adviser to President Barack Obama.

On Thursday, Ambien’s manufacturer was quick to respond on Twitter: “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.”

The scientific research, too, suggests there’s good reason to be skeptical. It’s true that Ambien on occasion produces significant side effects, including hallucinations and memory lapses. But blaming the drug for bilious tweeting is a stretch.

>> Could Barr’s use of Ambien have led to a racist taunt?

It’s a far-fetched claim at best.

Since they were introduced in the 1980s, the so-called “Z-drugs,” like Ambien (zolpidem) and Lunesta (eszopiclone), have become enormously popular. They are sedatives used primarily to treat insomnia, and users have reported all variety of adverse reactions.

The best known (and yes, these are most often associated with Ambien) are sleepwalking and memory blackouts, as well as nighttime feasting — the discovery on waking that, say, an entire bowl of spaghetti has been consumed, and the only plausible culprit is oneself.

Many people have described zombielike behavior when on Ambien. Former Rep. Patrick Kennedy, D-R.I., a mental health activist, in 2006 blamed the drug in part for his crashing a car into a security barricade at the U.S. Capitol.

But stories of such side effects tend to involve physical actions, often taken at night in a state of near amnesia — not specific and cogent comments made with apparent conscious awareness.

>> Could the drug cause a severe lapse in judgment?

It’s possible, to a point.

Most of the Z-drugs can have lingering mental effects the morning after use, and not just drowsiness. Verbal memory may slip; so may mental focus, the ability to read through a news article, to follow a complex email chain.

So-called working memory — the mental scratchpad where the brain manipulates numbers, names and images — may shrink temporarily. The evidence for these thinking effects is strongest for Ambien and Zimovane (zopiclone), compared with the others, according to a recent review, which also noted that other drugs in this class have not been so well studied.

Yet these effects, taken together, have much more in common with sleep deprivation than with Tourette-like outbursts of insults and epithets. Tourette’s episodes typically arrive as a deluge and generally have no rational connection to the person’s usual behavior.

Barr, by contrast, has a history of making inflammatory remarks, on Twitter and elsewhere.

>> Could the drug possibly have caused a “break” with reality, resulting in a racist insult?

Probably not.

Many people have reported hallucinations while taking Ambien. But these tend to be visual: letters swimming on the computer screen, figures in a familiar painting seeming to move, or daydreams so vivid they are like waking dreams — before the person snaps back into the here and now.

Sleep scientists suspect that at least some of these reactions represent “mixed states,” when mental processes of the slumbering brain leak into the patient’s waking hours. The nighttime forays to the fridge, for instance, are thought to result when the sleeping brain is active but the chemical that usually circulates to keep the body still is out of sync.

Still, these states tend to produce a spacey quality during waking hours, not the kind that lends itself to tossing off vituperative insults. For the agent causing that, Barr may have to look past the medicine cabinet.