Amazon Prime members  are eligible for free two-day delivery and discounts of up to 80% on generic medicines and 40% on prescribed brand-name drugs.

Customers need to provide some basic health information, such as whether they are pregnant, as well as date of birth, gender and insurance details.

Some questioned the wisdom of giving health data to a tech corporation.

Amazon Pharmacy vice-president TJ Parker said it was hoping to transform an industry that "can be inconvenient and confusing".

"We work hard behind the scenes to handle complications seamlessly so anyone who needs a prescription can understand their options, place their order at the lowest available price and have their medication delivered quickly," he said.