IL SB3733

Requires insurance companies offering prescription drug coverage through a formulary to immediately substitute brand name drugs with FDA-approved generic equivalents for plans amended, delivered, issued, or renewed in Illinois on or after January 1, 2021.

Allows insurers to alternatively move brand name drugs to a lower-cost formulary tier rather than substituting with generics, provided this reduces enrollee costs.

Applies to insurance companies transacting Class 1(b) or Class 2(a) kinds of insurance under the Illinois Insurance Code.

Requires insurers to notify insureds of any formulary changes, which can be accomplished by posting changes on the company's website.

Defines "brand name drug," "generic drug" (including biosimilars), and "formulary" for purposes of the regulation, with rulemaking authority granted to the Department of Insurance.