Walgreen’s (WAG) is off 88 cents to $28.95 and down 9.6 percent month-to-date. Implied volatility is up 5.5 percent to 38.5, from about 30 the week before, after a fight erupted between Walgreens and CVS over the two largest drug chain’s pharmacy benefits management arrangement. Walgreen’s announced the decision to end any new drug plans handled by the CVS PBM Network Monday. CVS retaliated Wednesday by saying it will divert more of its patients to its own drug stores. The battle is weighing on WAG shares and options action is picking up as well, with 22K contracts traded so far (55% puts). The action is scattered across a number of strikes and expiration months. The top trade looks like a bearish risk-reversal in the Jun 29 puts – 30 calls, apparently bought at 49 cents, 470X.