Spending on prescription drugs for health plans created under the Affordable Care Act increased last year at a rate more than three times that of other commercial plans and most government-run plans managed by Express Scripts Holding Co. Express Scripts, the largest manager of prescription drug plans for U.S. employers, on Tuesday said year-over-year spending per person for individual insurance plans sold on the Obamacare exchanges where it manages the pharmacy benefit rose 14 percent in 2016, driven by higher drug prices and utilization.