Health & Saf. Code, § 11158

(a) Except as provided in Section 11159 or in subdivision (b) of this section, no controlled substance classified in Schedule II shall be dispensed without a prescription meeting the requirements of this chapter. Except as provided in Section 11159 or when dispensed directly to an ultimate user by a practitioner, other than a pharmacist or pharmacy, no controlled substance classified in Schedule III, IV, or V may be dispensed without a prescription meeting the requirements of this chapter.

(b) A practitioner specified in Section 11150 may dispense a controlled substance classified in Schedule II, which may be from a hospital pharmacy inventory, directly to an ultimate user in either of the following circumstances:

(1) In an amount not to exceed a 72-hour supply for the patient in accordance with directions for use given by the dispensing practitioner only where the patient is not expected to require any additional amount of the controlled substance beyond the 72 hours.

(2) For the purpose of initiating maintenance treatment or detoxification treatment, or both, for a person with an opioid use disorder. Not more than a three-day supply of such medication may be dispensed to the person at one time while arrangements are being made for referral for treatment. Such emergency treatment may not be renewed or extended.

(c) Except as otherwise prohibited or limited by law, a practitioner specified in Section 11150, may administer controlled substances in the regular practice of their profession.