Amazon are buying online pharmacy PillPack making shares from other pharmaceutical comapnies plummet.
Shares in pharmacy chains CVS Health and Walgreens Boots Alliance plunged more than 8% in early trade.
The announcement confirmed earlier speculation that Amazon was interested in expanding into healthcare.
It expects to complete the deal in the second half of the year.
TJ Parker, PillPack's co-founder and chief executive, said: "Together with Amazon, we are eager to continue working with partners across the healthcare industry to help people throughout the US who can benefit from a better pharmacy experience."
