IL HB3519

Amends the Pharmacy Practice Act to allow pharmacists to substitute a prescription biosimilar product for a prescribed biological product under specified conditions.

Substitution is permitted only if the FDA has determined the biosimilar is interchangeable with the prescribed biological product and the prescriber has not prohibited substitution.

Requires pharmacy to inform the patient of the substitution and obtain patient agreement before dispensing the biosimilar product.

Mandates pharmacist notification to the prescriber within 3 business days of substitution, including the biosimilar's name and manufacturer, and requires the pharmacy to maintain written records of substitutions for at least 5 years.

Permits substitution only if the biosimilar costs less than the original product, or if costs more, the patient must be informed and agree to the higher cost; directs the Board to adopt implementing rules.