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The maker of the EpiPen will start selling a generic version in the wake of criticism about steep price increases.

Mylan said it expected to start selling a cheaper generic product "in several weeks" at a list price of $300 (£230).

That is about half the list price of the existing product, which is used in emergencies for severe food and insect allergies.

The cost of EpiPens in the US has risen by 500% in less than a decade.

Mylan said the generic version would be identical to the branded EpiPen, which costs $600 for two doses.

Allergy sufferers often have several pens - one to keep at home, as well as others at school or work, or in the car. They also expire after 12 months.

Mylan chief executive Heather Bresch said the company had spent hundreds of millions of dollars improving the product since buying the product from Merck in 2007.

"Our decision to launch a generic alternative to EpiPen is an extraordinary commercial response," she said. "We determined that bypassing the brand system in this case and offering an additional alternative was the best option."

'Heightened pressure'

The move is unusual because the branded version is still under patent and other rival treatments have failed to get regulatory clearance. The product generates annual sales of $1bn for Mylan.

Bernstein analyst Ronny Gal said: "We suspect Mylan will continue to receive some heat for its price increases and there will be heightened pressure on FDA [regulator the Food and Drug Administration] to bring competition to the market."

Ms Bresch also blamed the complex US health care system for the price rises and said that Mylan took just $274 of the $600 list price, while insurers, pharmacies and other parties shared the rest.

How much individuals pay for an EpiPen prescription can depend on their insurance coverage.

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Politicians and parents have challenged the price hikes, with Democratic presidential candidate Hillary Clinton calling them "outrageous" and unjustified.

The outcry over EpiPen price rises sent Mylan shares falling about 12% last week. The stock was flat at $43.04 in afternoon trading in New York.

Actor Sarah Jessica Parker, who had endorsed EpiPens, said last week she was ending her relationship with Mylan. She had previously spoken about the importance of the treatment to her family because of her son's peanut allergy.

Other drug makers including Valeant, Turing and Pfizer have come under fire in recent months for sharp price increases.