The drop of $63.51 (£40.21) to $450.50 (£285.30) was prompted by weaker-than-expected holiday iPhone sales, which were revealed on Wednesday.
Apple said it sold a record 47.8 million iPhones in the quarter ending in December, but this lagged behind the average analyst forecast of 50 million units.
It was the third straight quarter Apple missed Wall Street's revenue forecast, fanning fears that its dominance of consumer electronics is slipping.
Jefferies & Company analyst Peter Misek, who previously raised red flags about Apple cutting orders to suppliers, said the iPhone slowdown was "real and material" and here to stay.
"We think Apple is losing the screen-size wars," Mr Misek said.
Eighteen US brokerages have now cut their price targets on Apple shares, which slid to $451 (£285) at the opening of the Nasdaq exchange in New York.
Competition from Samsung and signs that the smartphone market may be close to saturation have slowed Apple's growth.
Questions remain over the company's ability to innovate after the death of iconic co-founder Steve Jobs.
But chief executive Tim Cook said he was delighted with the figures and insisted the company continued to focus on innovation.
"We're thrilled with record revenue of over $54bn (£34bn) and sales of over 75 million iOS devices in a single quarter," Mr Cook said.
"We're very confident in our product pipeline as we continue to focus on innovation and making the best products in the world."
Apple also sold 22.9 million iPads in the quarter, in line with expectations.
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