When the Medicare Part D prescription drug benefit was implemented in 2006, six drug classes were designated “protected classes.” Because responsibility for obtaining favorable drug prices depends on private insurers’ abilities to negotiate with pharmaceutical manufacturers using the threat of formulary exclusion, the protected class designation could undermine the insurers’ ability to control spending and utilization of drugs in these six classes. I estimate the effect of the protected class policy on total drug spending and utilization for Medicare beneficiaries. Following Abadie et al. (2010), I employ the synthetic control method on 2001-2011 data from the Medical Expenditure Panel Survey (MEPS). I find that protected status led to a significant increase of approximately $1.02 billion per class per year in overall spending for drugs in protected classes. Results for drug utilization were also positive but not significant. These results are important for informing the recent and ongoing deliberation by the Medicare program over whether to remove several classes from protection.