By Diane Bartz and Leroy Leo (Reuters) -The U.S. Federal Trade Commission is looking into how big pharmacy benefit managers like CVS Caremark affect pricing and patients’ access to prescription drugs at a time when costs of some medicines, even older ones like insulin, have skyrocketed, the agency said Tuesday. As part of the probe, the FTC is sending demands for information to CVS Health Corp’s Caremark, Humana Inc, Cigna Corp’s Express Scripts and UnitedHealth Group’s OptumRx, among others. Pharmacy benefit managers (PBMs) negotiate with drugmakers for rebates and lower fees on behalf of emp…