Restrictive Drug Coverage Policies can Induce Substantial Drug Exposure Misclassification in Pharmacoepidemiologic Studies

Drugs subject to restrictive coverage policies are substantially under-captured in administrative databases, leading to potential drug exposure misclassification in pharmacoepidemiologic studies relying on administrative databases. Pharmacoepidemiologic studies should clearly describe whether evaluated drugs are available as full benefits or subject to restrictive coverage policies and the potential impact on their results.