What information is NOT required on a prescription for a controlled substance?

The physician's phone number is not a required element on a prescription for a controlled substance. While including contact information is often a best practice that can assist in clarifying prescriptions or addressing potential issues with the pharmacy, it is not mandated by regulations regarding the prescribing of controlled substances.

In contrast, the patient's name, drug quantity, and physician signature are essential for a valid prescription. The patient's name ensures that the medication is being prescribed to the correct individual. The drug quantity specifies the amount that the patient is to receive, which is crucial for the correct management of the patient's health care and for regulatory compliance. Finally, the physician's signature serves as a means of verification, indicating that the prescriber has authorized the prescription, thus making it legally binding.