When are controlled substances allowed to be shipped?

Controlled substances are permitted to be shipped under the condition that they are sent specifically under a prescription. This aligns with regulations governing the handling of controlled substances, which stipulate that prescription requirements must be met to ensure safety, accountability, and proper oversight through the pharmacy dispensing process.

Shipping controlled substances without this requirement could lead to misuse or diversion, thereby exacerbating issues of substance abuse and regulatory noncompliance. These rules exist to maintain a structured framework where only licensed pharmacies can dispense these substances based on a valid prescription, which ultimately protects public health and safety.

Other scenarios presented in the options, such as shipping solely between licensed practitioners, emergencies, or outright prohibitions on shipping, would not align with the established regulatory framework for the transportation of controlled substances.