New Challenge for Medco

These days, pharmacy benefit managers can't seem to catch a break.

First, Wal-Mart (WMT Quote) starts selling generic drugs so cheaply that some people have started questioning whether other drug sellers, including PBMs, should be charging less for generics as well.

Then, a firm which publishes the "average wholesale prices" of brand-name drugs accepts new policies that could lower prices on branded drugs to boot. ...