Final answer:
A prescription for a controlled substance must be accompanied by a physician's signature and a DEA number, which is used to prevent illegal distribution and ensure adherence to federal regulations.
Step-by-step explanation:
Every prescription for a controlled substance requires the physician's signature and a DEA number. The DEA number is a unique identifier assigned to a health care provider by the United States Drug Enforcement Administration, allowing them to write prescriptions for controlled substances.
The importance of the DEA number lies in its use to track prescriptions and prevent the illegal distribution of controlled substances. The correct use of a DEA number ensures that prescriptions are filled and tracked in accordance with federal regulations regarding controlled substances.