Insurance, Health, Accident - As introduced, prohibits an insurer, pharmacy benefits manager, or third-party administrator from changing or conditioning the terms of health plan coverage based on availability of financial or other product assistance for a prescription drug; establishes certain procedures for calculating an enrollee's contribution to an applicable cost sharing requirement. - Amends TCA Title 4; Title 8; Title 10; Title 53; Title 56; Title 63; Title 68 and Title 71.

SB 420 prohibits insurers, pharmacy benefits managers, and third-party administrators in Tennessee from altering health plan coverage terms - such as cost-sharing or benefit design - based on whether a patient has access to prescription drug assistance programs (like manufacturer coupons or patient aid). This directly affects health plan enrollees who use such programs to lower drug costs. The bill requires insurers to calculate cost-sharing contributions based on actual patient payments, not external assistance, and applies to plans entered into or renewed on or after January 1, 2026. It aims to prevent insurers from penalizing patients for utilizing available drug cost-saving resources.