NEW YORK Now at Amazon.com : insulin and inhalers.

The online colossus opened an online pharmacy Tuesday that allows customers to order medication or prescription refills, and have them delivered to their front door in a couple of days.

The potential impact of Amazons arrival in the pharmaceutical space rippled through that sector immediately. The stocks of CVS Health Corp., Walgreens and Rite Aid all tumbled Tuesday.

The big chains rely on their pharmacies for a steady flow of shoppers who may also grab a snack or shampoo or groceries on the way out. All have upped online services and touted their abilities to deliver prescriptions and other goods as the COVID-19 pandemic has pushed more consumers to stay home. But Amazon.com has mastered these things, and its online store is infinitely larger, with millions of loyal shoppers already buying books, TVs and just about anything else.