WA SB5594

Beginning January 1, 2026, health carriers and prescription drug utilization management entities may require patients to try a biosimilar before providing coverage for an equivalent branded prescription drug, expanding existing step therapy rules that already applied to generic equivalents and interchangeable biological products.

Pharmacists may substitute therapeutically equivalent generic drugs or interchangeable biological products unless the prescriber explicitly indicates "dispense as written," eliminating the previous requirement for dual signature lines on prescription forms.

Pharmacists may substitute interchangeable biological products when the consumer's out-of-pocket cost for the interchangeable product is less than the cost for the prescribed biological product, changing the standard from wholesale price comparison to consumer cost comparison.

Qualified health plans offered through the Washington Health Benefit Exchange must comply with requirements to increase generic and biosimilar utilization and use evidence-based formularies.

Amends RCW 48.43.420, 41.05.410, 69.41.120, and 69.41.125 to implement these changes to prescription drug utilization management and pharmacy substitution practices.