The UK's medicines watchdog is recalling a batch of a heart drug after more fake tablets are discovered.
Pharmacists will be able to replace the recalled drug
The Medicines and Healthcare products Regulatory Agency (MHRA), with Pfizer, is now recalling Lipitor 20mg tablets bearing the lot number 067404K3.
In July 2005 and again in July 2006 the agency recalled another Lipitor batch, 004405K1, because of counterfeits found in the pharmaceutical supply chain.
Patients should not take tablets displaying either of these lot numbers.
Both batches carry authentic Lipitor numbers, so patients will be unable to tell whether their tablets are fake or real.
A spokesman for the agency stressed there was no immediate risk to patients, but said: "Because it is a counterfeit we cannot guarantee its quality.
"Any patient who has the Lipitor 20mg product with lot number 067404K3 or lot number 004405K1 anywhere on the pack should stop taking the tablets and contact their pharmacist."
Patients will then be given new supplies of the prescription-only drug. Patients should leave 24 hours between taking their last tablet and the first tablet of a new supply of Lipitor.
A total of 73 fake packets of Lipitor with the lot number 004405K1 were seized last year and 320 fake packets carrying the same lot number have been discovered since July this year.
Overall, 120,000 packets, each containing 28 tablets, were involved in those two incidents.
Pfizer, which makes Lipitor, called for more effort to be made by authorities in the UK and Europe to ensure the safety of medicines
Kate Lloyd, medical director of Pfizer UK, said: "Patient safety is our primary concern and we are seriously concerned at yet another discovery of counterfeit product masquerading as one of our medicines in the UK."
Pfizer UK's managing director Dr Olivier Brandicourt said: "Enough is enough, and we are calling for the MHRA and law enforcement agencies to conduct a full and thorough investigation into this incident and the general vulnerably of the medicines supply chain."
More than a million Britons are believed to take Lipitor for cardiovascular conditions.