(b) Notwithstanding section 17, a physician, physician assistant, dentist, podiatrist, optometrist, certified nurse midwife, nurse practitioner, psychiatric nurse mental health clinical specialist, nurse anesthetist, pharmacist as limited by said subsection (g) of said section 7 and section 24B 1/2 of said chapter 112, or veterinarian registered under said section 7, may, when acting in good faith and in the practice of medicine, dentistry, podiatry, optometry, nurse-midwifery, pharmacy or veterinary medicine or as a nurse, as the case may be, and when authorized by a physician, dentist, podiatrist, optometrist, nurse practitioner, physician assistant, certified nurse midwife, psychiatric nurse mental health clinical specialist, nurse anesthetist, or veterinarian in the course of such nurse's professional practice, dispense by delivering to an ultimate user a controlled substance in a single dose or in a quantity that is, in the opinion of such physician, dentist, podiatrist, optometrist, nurse practitioner, physician assistant, certified midwife, psychiatric nurse mental health clinical specialist, nurse anesthetist, pharmacist or veterinarian, essential for the treatment of a patient. The amount or quantity of any controlled substance dispensed under this subsection shall not exceed the quantity of a controlled substance necessary for the immediate and proper treatment of the patient until it is possible for the patient to have a prescription filled by a pharmacy. All controlled substances required by the patient as part of the patient's treatment shall be dispensed by prescription to the ultimate user in accordance with this chapter. see full law