IL SB1773

Amends the Illinois Controlled Substances Act to add a comprehensive definition of "fentanyl-related substances" as Schedule I controlled substances, covering compounds structurally derived from fentanyl through various chemical modifications including ring replacements and substitutions

Adds several specific opioids to Schedule I including brorphine, flunitazene, isotonitazene, and metonitazene, while removing individually listed fentanyl analogs that are now covered under the broader fentanyl-related substances definition

Schedules xylazine as a Schedule III controlled substance but exempts veterinary uses, including administration by licensed veterinarians, certified euthanasia technicians, and wildlife biologists working under veterinarian supervision

Consolidates synthetic cannabinoid structural class definitions into a single subsection, listing 24 specific chemical scaffolds (such as naphthoylindoles, phenylacetylindoles, and indazole carboxamides) that qualify as controlled synthetic cannabinoids

Adds a definition clarifying that "isomer" means optical isomer unless otherwise specified, and removes "positional" from the isomer definition for coca leaf derivatives in Schedule II