Pharmacy; interchangeable biological products; effective date. The CS to HB 3791 allows pharmacists to substitute a prescribed biological product for a FDAapproved interchangeable substitute, provided the prescribing physician has allowed the substitution and the pharmacy informs the patient of the substitution. The substitution must be communicated to the prescriber via electronic record within five business days. Neither the pharmacist nor the prescriber are subject to disciplinary action for failing to ensure the record is accessible to the prescriber.