Shares in AstraZeneca fell over 7 per cent in early trading today after regulators in Europe and the United States raised safety concerns about its anti-cholesterol treatment Crestor.
At 8.20 a.m., the shares were down 6.9 per cent at £22.03 , above a low of 21.82p.
The European Medicines Agency (EMEA) said late today it was investigating whether all patients taking Crestor should start on the lowest five-milligram dose following a referral from the UK sparked by "public health concerns".
EMEA's decision follows a Reuters story on Monday in which AstraZeneca said it was talking to European regulators about the potential wider use of a five-milligram dose of Crestor.
Late last night, US Food and Drug Administration reviewer Mr David Graham, who has accused the agency of being lax in monitoring drug safety, named Crestor as one of five medicines needing closer scrutiny.
AstraZeneca in the meantime reaffirmed the safety of Crestor in a statement last night .
Crestor is one of AstraZeneca's biggest new drug hopes as it looks to offset falling sales of ulcer pill Prilosec following the arrival of cheaper rival generic versions. Some analysts have forecast peak sales for Crestor at over $3 billion a year.
GlaxoSmithKline's Serevent treatment for asthma was another of the five drugs. GSK's shares were 3.7 per cent lower at £11.48.