In its earnings presentation this week, CVS offered a timeframe on the expected merger while rebutting criticism that PBMs spur higher drug prices.

Investors were wary of the deal from the start, and since the deal was announced the threats to Express Scripts's business have only increased.

The move gives Amazon an immediate national drug network and represents a formidable threat to pharmacy chains.

Munger thought the article was so useful that he blindly mailed Gawande a $20,000 check, Buffett told CNBC at the time.

In an attempt to shame drugmakers into keeping list prices down, a new federal dashboard highlights drugs with particularly rapid increases in unit costs.

Shares of drug-supply-chain stocks have been in a tizzy for months over what Amazon might do.

The retail giant is said to be in talks with online startup PillPack, which pre-sorts pills into date- and time-stamped packets for patients who take multiple drugs.

Using tactics that have drawn the attention of federal regulators and attracted lawsuits, drug plans and insurers have boxed out their smaller partners so they can take the business for themselves.