Final answer:
Only one controlled substance can be prescribed per prescription blank due to DEA regulations, although multiple non-controlled substances may be listed on the same blank.
Step-by-step explanation:
The number of control substances that can appear on a single prescription blank can vary based on regional regulations and the type of prescription form being used. In the United States, the Drug Enforcement Administration (DEA) requires that for controlled substances, each prescription must be written on a separate prescription blank. This means only one controlled substance can be issued per prescription blank. However, for non-controlled substances, multiple medications can be prescribed on the same form, depending on the space available and the prescribing doctor's discretion.
This rule for controlled substances is a part of efforts to prevent abuse and prescription fraud, ensuring a more secure and traceable system for dispensing medications that have potential for abuse or dependency.