Doctors in the United States have shunned GlaxoSmithKline's diabetes drug Avandia since a study was published last week linking the drug to heart-attack risk, according to daily prescription data.
Information from market research group Impact RX indicates Avandia's share of the market for newly prescribed oral anti-diabetics fell to approximately zero from around 10% in the two days after the article was published on May 21.
"This reaction is far worse than we had anticipated and suggests that there could be as much as 22% downside risk to GSK's near term earnings, suggesting that there is still further downside to GSK's share price, " Deutsche Bank analysts, citing the prescription data, said in a note.