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(CNN) -- The Food and Drug Administration advised concerned consumers Thursday to stop taking a popular cholesterol drug that may be contaminated with specks of glass if the pills came from one of 41 recalled lots.
The recall of generic Lipitor was initiated nearly three weeks ago by Ranbaxy Pharmaceuticals, but this is the first time the FDA -- or anyone else -- has told consumers to stop taking the drug.
The FDA also announced Thursday that Ranbaxy would stop making atorvastatin while it investigates how the glass might have gotten into the drug.
Even with these new guidelines, some pharmacies are still telling customers it's safe to take the drug.
"Patients should continue to proceed as they normally would," said Brian Henry, vice president of corporate communications at Express Scripts, on Thursday. He added that the company would not give customers refunds for the generic Lipitor, or atorvastatin.
Henry explained that this was a "pharmacy-level recall," meaning pharmacies must stop dispensing contaminated lots of the drug, but consumers could keep taking what they already had at home -- even though the FDA has confirmed that some of the contaminated drug may have reached consumers.
Pharmacists at several CVS stores also told customers it was OK to keep taking Ranbaxy's atorvastatin but said they would replace the drug at a patient's request.
"This whole thing is confusing for consumers," said Lisa Gill, editor of prescription drugs at Consumer Reports.
She also expressed concern that it took the FDA nearly three weeks to issue guidance to consumers.
"It's not clear why it took them so long," she said. "It's surprising."
FDA spokeswoman Sarah Clark-Lynn declined to comment on the reasons behind the delay.
In its statement Thursday, the FDA said that the glass particles were "similar to the size of a grain of sand" and that "the possibility of adverse events related to the recalled product appear to be low."
Making matters potentially even more confusing, the FDA directed concerned consumers to call their pharmacies to see whether their pills had been recalled, as not all lots of the drug are effected.
However, pharmacists say they have no way of figuring out what lot number a bottle of pills came from.
"The ability to tie a specific prescription to a lot number would be very difficult," said Ronna Hauser, vice president of policy and regulatory affairs at the National Community Pharmacists Association.
Ranbaxy, India's largest pharmaceutical company and the 12th largest generics maker in the world, has had quality problems in the past.
The FDA has accused the company of "a pattern of systemic fraudulent conduct," including taking shortcuts in crucial quality tests. So widespread and grave was the misbehavior that in 2008 the FDA barred Ranbaxy from importing 30 drugs into the United States.