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 Ms. 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 Representative Patrick Kennedy, Democrat of Rhode Island and current mental health activist, in 2006 blamed the drug in part for his crashing a car into a security barricade at the United States Capitol.