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The "Sex and the City" star was a spokeswoman for the company's "Anaphylaxis for Reel" campaign, which sought to bring awareness to its anaphylactic shock products, including the EpiPen.
She is also a customer. She purchases the EpiPen for her son, James Wilkie, in case of emergency reactions as a result of his peanut allergy.
Parker posted her statement about cutting ties with the company on Instagram Thursday. In it, she said that she is "disappointed, saddened, and deeply concerned" about the company's price hike.
The price hike, which was revealed on Wednesday, resulted in furious reactions from the public and political leaders, including Hillary Clinton. At first, Mylan said the price increase was partly a result of President Barack Obama and the Affordable Care Act, aka Obamacare.
Mylan then announced it would be implementing new measures that would bring the cost down for patients, including $300 coupons and increasing income assistance in buying the medication.