Final answer:
Pharmacists with additional prescribing authorization, and in some regions nurse practitioners, can substitute prescribed medications with drugs expected to have similar effects.
Step-by-step explanation:
The individuals who can engage in substituting a prescribed medication with another drug that is expected to have a similar therapeutic effect are typically pharmacists with additional prescribing authorization. This role goes beyond the traditional responsibilities of a pharmacist, which include dispensing drugs prescribed by a doctor and advising on their proper use. In some regions, nurse practitioners also have the authority to prescribe and make substitutions. It is important to note that the legality and extent of prescriptive privileges can vary depending on the jurisdiction and specific regulations in place.