Which of the following practitioners is designated by a DEA number starting with the letter M?

In the context of the Drug Enforcement Administration (DEA) numbering system, a DEA number that begins with the letter "M" is assigned to practitioners who are authorized to prescribe controlled substances, with a specific focus on Nurse Practitioners (NPs) and Physician Assistants (PAs) who have obtained certification to do so.

Nurse Practitioners, as advanced practice registered nurses, have the ability to prescribe medications, including controlled substances, within the scope of their practice and according to state regulations. This authority is reflected in their DEA registration, which starts with the letter "M."

In contrast, pharmacists are identified by DEA numbers that start with the letter "P" or "R," chiropractors are generally not authorized to prescribe controlled substances and do not receive a specific DEA number for that purpose, and physical therapists are also not authorized to prescribe medications, including controlled substances, and thus do not have a DEA number. Therefore, the designation of a DEA number starting with "M" is specifically reserved for Nurse Practitioners.