Final answer:
The legal limit for day supply and quantity of a C-II prescription depends on federal and state regulations, typically with no specific maximum at the federal level but possible state restrictions such as a 30-day supply limit.
Step-by-step explanation:
The legal limit for a day supply and quantity for a Schedule II (C-II) controlled substance prescription can vary by jurisdiction, but federal regulations in the United States generally do not specify a maximum day supply for a C-II prescription. However, the prescribing practitioner must determine a legitimate medical purpose for the quantity prescribed, and it should be consistent with the usual course of treatment.
A prescription for a C-II substance typically cannot be refilled; a new prescription is required for additional medication. In some states, the law may limit the day supply to a 30-day maximum, but this can vary. Clinicians must comply not only with federal regulations but also with the state laws that can impose stricter controls.