Analysts at Morgan Stanley downgraded the stock to equal-weight from overweight while cutting its price target to $36 from $57 a share.
Analyst Ricky Goldwasser said that "the crossroads of internet and healthcare just got a little more crowded," in explaining the firm's downgrade.
"What surprised us is the breadth of pharmacy network included in Amazon’s PrimeRx offering. By entering into an exclusive agreement with Express Scripts/Cigna, Amazon is tapping into Express’ pharmacy network to quickly gain scale," Goldwasser said.
Meanwhile, analysts at J.P. Morgan downgraded the stock to underweight from neutral while citing the competitive threat from Amazon.
GoodRX, which debuted in late September, fell 6.1% to $34 a share, nearing its initial public offering price of $33. Amazon shares were down 0.45% to $3,121 on Wednesday.
Amazon's new offering comes more than two years after Seattle-based Amazon's $753 million acquisition of PillPack, an online pharmacy known for organizing pills into packets that also delivers drugs directly to consumers’ homes.
Previously, U.S. Amazon customers were redirected to PillPack for orders.
Shoppers can pay using their health insurance. Prime members who don’t use their insurance are eligible for discounts on generic and brand-name drugs on Amazon’s site or at about 50,000 participating pharmacies, Amazon said.