The pharmacy industry, which has been grappling with a range of challenges over the past few years, is now facing additional pressure with the launch of same-day medication delivery by the nation's two largest retailers.

Earlier this week, Walmart announced plans to offer same-day medication delivery across the country early next year. The company will leverage its 4,600 outlets containing pharmacies to send out prescription drugs, according to a Financial Times article. The announcement followed news earlier this month that Amazon is expanding its same-day medication delivery to nearly half of the US population by the end of next year. It plans to add pharmacy services sites in 20 cities, including Philadelphia, Dallas and San Diego.

Amazon said its same-day service would mean an order received by 4 p.m. would arrive by 10 p.m. Walmart said its same-day prescription delivery times could be as short as half an hour.