(1) Except as provided in subsection (2) of this section, for health plans that include prescription drug coverage issued or renewed on or after January 1, 2025, a health carrier or its health care benefit manager may not require the substitution of a nonpreferred drug with a preferred drug in a given therapeutic class, or increase an enrollee's cost-sharing obligation mid-plan year for the drug, if the prescription is for a refill of an antipsychotic, antidepressant, antiepileptic, or other drug prescribed to the enrollee to treat a serious mental illness, the enrollee is medically stable on the drug, and a participating provider continues to prescribe the drug.

(2) Nothing in this section prohibits:

(a) The carrier from requiring generic substitution during the current plan year;

(b) The carrier from adding new drugs to its formulary during the current plan year;

(c) The carrier from removing a drug from its formulary for reasons of patient safety concerns, drug recall or removal from the market, or medical evidence indicating no therapeutic effect of the drug; or

(d) A participating provider from prescribing a different drug that is covered by the plan and medically appropriate for the enrollee.

(3) For the purposes of this section:

(a) "Refill" means a second or subsequent filling of a previously issued prescription.

(b) "Serious mental illness" means a mental disorder, as defined in the most recent edition of the diagnostic and statistical manual of mental disorders published by the American psychiatric association, that results in serious functional impairment that substantially interferes with or limits one or more major life activities.