PROHIBITS PHARMACY BENEFIT MANAGERS FROM MAKING CERTAIN RETROACTIVE REDUCTIONS IN CLAIM PAYMENTS TO PHARMACIES:  After the date of receipt of a clean claim for payment made by a pharmacy, a pharmacy benefits manager shall not retroactively reduce payment on the claim, either directly or indirectly, through aggregated effective rate or otherwise, except if the claim is found not to be clean during the course of a routine audit performed pursuant to an agreement between the pharmacy benefits manager and the pharmacy.  Nothing in the bill prohibits any retroactive increase in payment to a pharmacy pursuant to a written agreement between the pharmacy benefits manager and the pharmacy.