Which of the following is a requirement of telephone prescriptions for controlled substances?

The requirement that telephone prescriptions for controlled substances must be directly provided by the prescriber is rooted in regulatory standards aimed at ensuring patient safety and proper control over prescription medications. Controlled substances are drugs that have a high potential for abuse or dependency, which makes it crucial that their prescribing is managed carefully.

When a prescriber calls in a prescription for a controlled substance, it ensures that the prescribing is intentional and validated by the licensed individual responsible for the patient's care. This prevents unauthorized or fraudulent prescriptions and contributes to a more secure medication dispensing process. Regulations often stipulate that only the prescriber can provide these prescriptions via phone to protect patients and ensure that no miscommunication or unauthorized instructions occur.

Given the significance of this requirement, it is clear why this option is deemed the correct answer, as it aligns with the legal and ethical standards for handling controlled substances in the healthcare system.