The largest pharmacy benefit manager in the country, Express Scripts (NASDAQ: ESRX), has seen its shares fall under serious pressure since reporting earnings. To keep investors up to speed with the stock, Motley Fool health care bureau chief Brenton Flynn breaks down some of the key changes to the company's latest SEC filings and compares his findings with the commentary from one of its big customers, UnitedHealth Group (NYSE:UNH).

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